added alsa
authorThomas Vander Stichele <thomas@apestaart.org>
Sun, 23 Dec 2001 00:25:30 +0000 (00:25 +0000)
committerThomas Vander Stichele <thomas@apestaart.org>
Sun, 23 Dec 2001 00:25:30 +0000 (00:25 +0000)
Original commit message from CVS:
added alsa

TODO
configure.ac
ext/Makefile.am
ext/alsa/Makefile.am [new file with mode: 0644]
ext/alsa/README [new file with mode: 0644]
ext/alsa/gstalsa.c [new file with mode: 0644]
ext/alsa/gstalsa.h [new file with mode: 0644]

diff --git a/TODO b/TODO
index f229dca..bfcbdf4 100644 (file)
--- a/TODO
+++ b/TODO
@@ -17,3 +17,4 @@
 
 * check options in a52, it has some arch stuff and some opti stuff that 
   looks dodgy
+
index 89fe6d4..1e4660c 100644 (file)
@@ -1152,6 +1152,7 @@ sys/xvideo/Makefile
 ext/Makefile
 ext/a52/Makefile
 ext/aalib/Makefile
+ext/alsa/Makefile
 ext/audiofile/Makefile
 ext/esd/Makefile
 ext/lame/Makefile
index 2b2aca0..ff91846 100644 (file)
@@ -10,6 +10,12 @@ else
 AALIB_DIR=
 endif
 
+if USE_ALSA
+ALSA_DIR=alsa
+else
+ALSA_DIR=
+endif
+
 if USE_AUDIOFILE
 AUDIOFILE_DIR=audiofile
 else
@@ -47,8 +53,8 @@ VORBIS_DIR=
 endif
 
 
-SUBDIRS=$(A52_DIR) $(AALIB_DIR) $(AUDIOFILE_DIR) $(ESD_DIR) \
+SUBDIRS=$(A52_DIR) $(AALIB_DIR) $(ALSA_DIR) $(AUDIOFILE_DIR) $(ESD_DIR) \
         $(LAME_DIR) $(MAD_DIR) \
        $(SDL_DIR) $(VORBIS_DIR)
 
-DIST_SUBDIRS=a52 aalib audiofile esd lame mad sdl vorbis
+DIST_SUBDIRS=a52 aalib alsa audiofile esd lame mad sdl vorbis
diff --git a/ext/alsa/Makefile.am b/ext/alsa/Makefile.am
new file mode 100644 (file)
index 0000000..75ff111
--- /dev/null
@@ -0,0 +1,13 @@
+plugindir = $(libdir)/gst
+
+plugin_LTLIBRARIES = libgstalsa.la
+
+libgstalsa_la_SOURCES = gstalsa.c
+
+noinst_HEADERS = gstalsa.h
+
+libgstalsa_la_CFLAGS = $(ALSA_CFLAGS) $(GST_CFLAGS)
+libgstalsa_la_LIBADD = $(ALSA_LIBS)
+
+EXTRA_DIST = README
+
diff --git a/ext/alsa/README b/ext/alsa/README
new file mode 100644 (file)
index 0000000..406b83a
--- /dev/null
@@ -0,0 +1,64 @@
+0.0 History
+-----------
+
+This plugin was originally written by Thomas Nyberg <thomas@codefactory.se> for
+ALSA 0.5.x. It was updated and changed quite a bit in September 2001 by Andy
+Wingo for use with ALSA 0.9.x.
+
+1.0 Introduction
+----------------
+
+This plugin was designed for use with ALSA 0.9.x, using other versions most
+assuredly will not work.
+
+The plugin will probe which cards and pcm-devices that are availible, and then
+it tries to determine their capabilities. This will allow the use of multiple
+cards with multiple pcm-devices - at the same time! Since I only have one card
+on my system, as of yet, I haven't had the chance to try this out.
+
+2.0 How to use it
+-----------------
+
+Since we can have multiple soundcards, each having the same name - and also
+multiple pcm-devices on each card, a problem with naming occurs. When
+the alsa-plugins are initialized, a factory is created for each card and 
+pcm-device on the system. 
+
+On my desktop, I have the following:
+
+wingo@cebreiro:~/src/gstreamer$ gstreamer-inspect alsa
+INFO (  339:-1) Initializing GStreamer Core Library
+INFO (  339:-1) CPU features: (808009bf) MMX 3DNOW 
+Plugin Details:
+  Name:         alsa
+  Long Name:    Alsa plugin library
+  Filename:     /usr/lib/gst/libalsa.so
+
+  ES1370/1_sink: ES1370 DAC2/ADC
+  ES1370/2_sink: ES1370 DAC1
+  ES1370/1_src: ES1370 DAC2/ADC
+  alsasink: default alsa sink
+  alsasrc: default alsa src
+
+My particular card has 4 channel out and 2 channel in. As you can see, each of
+these devices are stereo. The alsasink and alsasrc elements correspond to the
+default alsa devices.
+
+3.0 License
+-----------
+
+ALSA 0.9.x isn't very well documented, so I had to rely on a number of different
+sources for guidance. One of the main sources of inspiration was Paul Davis'
+audioengine (available in quasimodo's cvs tree,
+http://quasimodo.sourceforge.net/), from which I took a large amount of code.
+Since that project is licensed under the GPL, it was only right that I license
+the updated version of this plugin under the GPL as well. What, in my
+understanding, this means for the end user is that you cannot use the ALSA
+plugin with a non-GPL program. If in doubt, please refer to the COPYING file
+located in this directory.
+
+
+
+
+
+
diff --git a/ext/alsa/gstalsa.c b/ext/alsa/gstalsa.c
new file mode 100644 (file)
index 0000000..8cd8afc
--- /dev/null
@@ -0,0 +1,1433 @@
+/*
+    Copyright (C) 2001 CodeFactory AB
+    Copyright (C) 2001 Thomas Nyberg <thomas@codefactory.se>
+    Copyright (C) 2001 Andy Wingo <apwingo@eos.ncsu.edu>
+
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public
+    License as published by the Free Software Foundation; either
+    version 2 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    General Public License for more details.
+
+    You should have received a copy of the GNU General Public
+    License along with this library; if not, write to the Free
+    Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include <stdlib.h>
+#include "alsa.h"
+
+static GstElementDetails gst_alsa_sink_details = {  
+    "Alsa Sink",
+    "Sink/Audio",
+    "Output to a sound card via ALSA: see plugins/alsa/README for more info",
+    VERSION,
+    "Thomas Nyberg <thomas@codefactory.se>, "
+    "Andy Wingo <apwingo@eos.ncsu.edu>",
+    "(C) 2001 "
+};
+
+static GstElementDetails gst_alsa_src_details = {  
+    "Alsa Src",
+    "Source/Audio",
+    "Read from a sound card via ALSA: see plugins/alsa/README for more info",
+    VERSION,
+    "Thomas Nyberg <thomas@codefactory.se>, "
+    "Andy Wingo <apwingo@eos.ncsu.edu>"
+    "(C) 2001",
+};
+
+static GstElement *parent_class = NULL;
+
+static void gst_alsa_init(GstAlsa *this);
+static void gst_alsa_class_init(GstAlsaClass *klass);
+
+static GstPadTemplate *gst_alsa_src_pad_factory();
+static GstPadTemplate *gst_alsa_src_request_pad_factory();
+static GstPadTemplate *gst_alsa_sink_pad_factory();
+static GstPadTemplate *gst_alsa_sink_request_pad_factory();
+
+static GstPad* gst_alsa_request_new_pad (GstElement *element, GstPadTemplate *templ, const
+                                         gchar *name);
+
+static void gst_alsa_set_property(GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec);
+static void gst_alsa_get_property(GObject *object, guint prop_id, GValue *value, GParamSpec *pspec);
+static GstElementStateReturn gst_alsa_change_state(GstElement *element);
+static GstPadNegotiateReturn gst_alsa_negotiate(GstPad *pad, GstCaps **caps, gpointer *user_data);
+
+static GstCaps* gst_alsa_caps (GstAlsa *this);
+
+static gboolean gst_alsa_open_audio(GstAlsa *this);
+static gboolean gst_alsa_start_audio(GstAlsa *this);
+static void gst_alsa_stop_audio(GstAlsa *this);
+static void gst_alsa_close_audio(GstAlsa *this);
+
+static gboolean gst_alsa_set_params(GstAlsa *this);
+static void gst_alsa_loop (GstElement *element);
+static gboolean gst_alsa_sink_process (GstAlsa *this, snd_pcm_uframes_t frames);
+static gboolean gst_alsa_src_process (GstAlsa *this, snd_pcm_uframes_t frames);
+
+static gboolean gst_alsa_get_channel_addresses (GstAlsa *this);
+static void gst_alsa_release_channel_addresses (GstAlsa *this);
+
+static void gst_alsa_sink_silence_on_channel (GstAlsa *this, guint32 chn, guint32 nframes);
+static void memset_interleave (char *dst, char val, unsigned int bytes, 
+                               unsigned int unit_bytes, 
+                               unsigned int skip_bytes);
+
+
+enum {
+    ARG_0,
+    ARG_DEVICE,
+    ARG_FORMAT,
+    ARG_CHANNELS,
+    ARG_RATE,
+    ARG_PERIODCOUNT,
+    ARG_PERIODFRAMES
+};
+
+GType
+gst_alsa_get_type (void) 
+{
+  static GType alsa_type = 0;
+
+  if (!alsa_type) {
+    static const GTypeInfo alsa_info = {
+      sizeof(GstAlsaClass),
+      NULL,
+      NULL,
+      NULL,
+      NULL,
+      NULL,
+      sizeof(GstAlsa),
+      0,
+      NULL,
+    };
+    alsa_type = g_type_register_static (GST_TYPE_ELEMENT, "GstAlsa", &alsa_info, 0);
+  }
+  return alsa_type;
+}
+
+GType
+gst_alsa_sink_get_type (void) 
+{
+  static GType alsa_type = 0;
+
+  if (!alsa_type) {
+    static const GTypeInfo alsa_info = {
+      sizeof(GstAlsaClass),
+      NULL,
+      NULL,
+      (GClassInitFunc)gst_alsa_class_init,
+      NULL,
+      NULL,
+      sizeof(GstAlsa),
+      0,
+      (GInstanceInitFunc)gst_alsa_init,
+    };
+    alsa_type = g_type_register_static (GST_TYPE_ALSA, "GstAlsaSink", &alsa_info, 0);
+  }
+  return alsa_type;
+}
+
+GType
+gst_alsa_src_get_type (void) 
+{
+  static GType alsa_type = 0;
+
+  if (!alsa_type) {
+    static const GTypeInfo alsa_info = {
+      sizeof(GstAlsaClass),
+      NULL,
+      NULL,
+      (GClassInitFunc)gst_alsa_class_init,
+      NULL,
+      NULL,
+      sizeof(GstAlsa),
+      0,
+      (GInstanceInitFunc)gst_alsa_init,
+    };
+    alsa_type = g_type_register_static (GST_TYPE_ALSA, "GstAlsaSrc", &alsa_info, 0);
+  }
+  return alsa_type;
+}
+
+static GstPadTemplate*
+gst_alsa_src_pad_factory(void)
+{
+    static GstPadTemplate *template = NULL;
+    
+    if (!template)
+        template = gst_padtemplate_new("src", GST_PAD_SRC, GST_PAD_SOMETIMES, 
+                                       gst_caps_new("src", "audio/raw", NULL),
+                                       NULL);
+    
+    return template;
+}
+
+static GstPadTemplate*
+gst_alsa_src_request_pad_factory(void)
+{
+    static GstPadTemplate *template = NULL;
+    
+    if (!template)
+        template = gst_padtemplate_new("src%d", GST_PAD_SRC, GST_PAD_REQUEST, 
+                                       gst_caps_new("src", "audio/raw",
+                                                    gst_props_new("channels", GST_PROPS_INT(1), NULL)),
+                                       NULL);
+    
+    return template;
+}
+
+static GstPadTemplate*
+gst_alsa_sink_pad_factory(void)
+{
+    static GstPadTemplate *template = NULL;
+    
+    if (!template)
+        template = gst_padtemplate_new("sink", GST_PAD_SINK, GST_PAD_SOMETIMES, 
+                                       gst_caps_new("sink", "audio/raw", NULL),
+                                       NULL);
+    
+    return template;
+}
+
+static GstPadTemplate*
+gst_alsa_sink_request_pad_factory(void)
+{
+    static GstPadTemplate *template = NULL;
+    
+    if (!template)
+        template = gst_padtemplate_new("sink%d", GST_PAD_SINK, GST_PAD_REQUEST, 
+                                       gst_caps_new("sink-request", "audio/raw",
+                                                    gst_props_new("channels", GST_PROPS_INT(1), NULL)),
+                                       NULL);
+    
+    return template;
+}
+
+static void
+gst_alsa_class_init(GstAlsaClass *klass)
+{
+    GObjectClass *object_class;
+    GstElementClass *element_class;
+    
+    object_class = (GObjectClass *)klass;
+    element_class = (GstElementClass *)klass;
+    
+    if (parent_class == NULL)
+        parent_class = g_type_class_ref(GST_TYPE_ELEMENT);
+    
+    object_class->get_property = gst_alsa_get_property;
+    object_class->set_property = gst_alsa_set_property;
+    
+    g_object_class_install_property(G_OBJECT_CLASS(klass), ARG_DEVICE,
+                                    g_param_spec_string("device","device","alsa device: please see README for details",
+                                                     "default",
+                                                     G_PARAM_READWRITE));
+    g_object_class_install_property(G_OBJECT_CLASS(klass), ARG_FORMAT,
+                                    g_param_spec_int("format","format","format",
+                                                     0, SND_PCM_FORMAT_LAST, SND_PCM_FORMAT_S16,
+                                                     G_PARAM_READWRITE));
+    g_object_class_install_property(G_OBJECT_CLASS(klass), ARG_CHANNELS,
+                                    g_param_spec_int("channels","channels","channels",
+                                                     1, 64, 1,
+                                                     G_PARAM_READWRITE));
+    g_object_class_install_property(G_OBJECT_CLASS(klass), ARG_RATE,
+                                    g_param_spec_int("rate","rate","rate",
+                                                     8000, 192000, 44100,
+                                                     G_PARAM_READWRITE));
+    g_object_class_install_property(G_OBJECT_CLASS(klass), ARG_PERIODCOUNT,
+                                    g_param_spec_int("period_count","period count","period count",
+                                                     2, 64, 2,
+                                                     G_PARAM_READWRITE));
+    g_object_class_install_property(G_OBJECT_CLASS(klass), ARG_PERIODFRAMES,
+                                    g_param_spec_int("period_frames","period frames","period frames",
+                                                     64, 4096, 256,
+                                                     G_PARAM_READWRITE));
+    
+    element_class->change_state = gst_alsa_change_state;
+    
+    element_class->request_new_pad = gst_alsa_request_new_pad;
+}
+
+static void
+gst_alsa_init(GstAlsa *this)
+{
+    /* init values */
+    this->handle = NULL;
+    
+    /* i tried to trim this down to only the essentials needed for proper
+     * functioning; we'll be setting this values 'in earnest' when caps come */
+    
+    this->rate = 44100;
+    this->channels = 2;
+    
+    /* i wish i could leave these to defaults, but when caps come and typically
+     * the number of channels doubles, you can't have the default count and size
+     * that alsa gives you from the pre-caps setup apply to the post-caps setup
+     * due to internal hw buffer size restrictions. these values seem to be
+     * pretty common, though, although not pushing latency limits */
+    this->period_count = 2;
+    this->period_frames = 4096;
+    
+    this->device = g_strdup("default");
+    
+    /* is this right? */
+    GST_FLAG_SET(this, GST_ELEMENT_THREAD_SUGGESTED);
+    
+    if (G_OBJECT_TYPE(this) == GST_TYPE_ALSA_SRC) {
+        this->stream = SND_PCM_STREAM_CAPTURE;
+        this->pads = g_list_append(NULL, g_new0(GstAlsaPad, 1));
+        GST_ALSA_PAD(this->pads)->pad = gst_pad_new_from_template(gst_alsa_src_pad_factory(), "src");
+        this->process = gst_alsa_src_process;
+        this->format = SND_PCM_FORMAT_S16; /* native endian */
+    } else if (G_OBJECT_TYPE(this) == GST_TYPE_ALSA_SINK) {
+        this->stream = SND_PCM_STREAM_PLAYBACK;
+        this->pads = g_list_append(NULL, g_new0(GstAlsaPad, 1));
+        GST_ALSA_PAD(this->pads)->pad = gst_pad_new_from_template(gst_alsa_sink_pad_factory(), "sink");
+        this->process = gst_alsa_sink_process;
+        this->format = SND_PCM_FORMAT_UNKNOWN; /* we don't know until caps are
+                                                * set */
+    } else {
+        g_print("you cannot instantiate an object of type gstalsa. use alsasink or alsasrc instead.\n");
+        G_BREAKPOINT();
+        return;
+    }
+    
+    GST_ALSA_PAD(this->pads)->channel = -1;
+    
+    this->data_interleaved = TRUE;
+    
+    gst_element_add_pad(GST_ELEMENT(this), GST_ALSA_PAD(this->pads)->pad);
+    
+    gst_pad_set_negotiate_function(GST_ALSA_PAD(this->pads)->pad, gst_alsa_negotiate);
+    gst_element_set_loop_function(GST_ELEMENT(this), gst_alsa_loop);
+}
+
+static GstPad*
+gst_alsa_request_new_pad (GstElement *element, GstPadTemplate *templ, const gchar *name) 
+{
+    GstAlsa *this;
+    gint channel;
+    gchar *newname;
+    GList *l;
+    GstAlsaPad *pad;
+    
+    g_return_val_if_fail (this = GST_ALSA(element), NULL);
+    
+    /* you can't request a pad if the non-request pad is connected */
+    g_return_val_if_fail (this->data_interleaved == FALSE ||
+                          this->pads == NULL || 
+                          GST_ALSA_PAD(this->pads) == NULL ||
+                          GST_ALSA_PAD(this->pads)->pad == NULL ||
+                          GST_PAD_PEER(GST_ALSA_PAD(this->pads)->pad) == NULL, 
+                          NULL);
+    
+    if (name) {
+        if (sscanf(name, templ->name_template, &channel) != 1) {
+            g_warning("invalid pad name %s (trying to fit with %s)", name,
+                      templ->name_template);
+            return NULL;
+        }
+        l = this->pads;
+        while (l) {
+            if (GST_ALSA_PAD(l)->channel == channel) {
+                g_warning("requested channel %d already in use.", channel);
+                return NULL;
+            }
+            l = l->next;
+        }
+    } else {
+        l = this->pads;
+        channel = 0;
+        while (l) {
+            if (GST_ALSA_PAD(l)->channel > channel)
+                channel = GST_ALSA_PAD(l)->channel;
+            l = l->next;
+        }
+    }
+    
+    newname = g_strdup_printf (templ->name_template, channel);
+    
+    pad = g_new0(GstAlsaPad, 1);
+    pad->channel = channel;
+    pad->pad = gst_pad_new_from_template (templ, newname);
+    gst_element_add_pad (GST_ELEMENT (this), pad->pad);
+    gst_pad_set_negotiate_function(pad->pad, gst_alsa_negotiate);
+    
+    if (this->data_interleaved && this->pads) {
+        gst_element_remove_pad (GST_ELEMENT (this), GST_ALSA_PAD(this->pads)->pad);
+        g_free (GST_ALSA_PAD(this->pads));
+        g_list_free (this->pads);
+        this->pads = NULL;
+    }
+    
+    this->pads = g_list_append(this->pads, pad);
+    
+    // FIXME: allow interleaved access (for hw:N,M access on consumer hardware)
+
+    if (this->data_interleaved) {
+        this->channels = pad->channel + 1;
+        this->data_interleaved = FALSE;
+    } else {
+        this->channels = MAX(this->channels, pad->channel + 1);
+    }
+    
+    return pad->pad;
+}
+
+static void
+gst_alsa_set_property(GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec)
+{
+    GstAlsa *this;
+    
+    this = (GstAlsa *)object;
+    switch (prop_id) {
+    case ARG_DEVICE:
+        if (this->device)
+            g_free (this->device);
+        this->device = g_strdup(g_value_get_string (value));
+        break;
+    case ARG_FORMAT:
+        this->format = g_value_get_int (value);
+        break;
+    case ARG_CHANNELS:
+        this->channels = g_value_get_int (value);
+        break;
+    case ARG_RATE:
+        this->rate = g_value_get_int (value);
+        break;
+    case ARG_PERIODCOUNT:
+        this->period_count = g_value_get_int (value);
+        this->buffer_frames = this->period_count * this->period_frames;
+        break;
+    case ARG_PERIODFRAMES:
+        this->period_frames = g_value_get_int (value);
+        this->buffer_frames = this->period_count * this->period_frames;
+        break;
+    default:
+        GST_DEBUG(0, "Unknown arg");
+        return;
+    }
+    
+    if (GST_STATE(this) == GST_STATE_NULL)
+        return;
+    
+    if (GST_FLAG_IS_SET(this, GST_ALSA_RUNNING)) {
+        gst_alsa_stop_audio(this);
+        gst_alsa_set_params(this);
+        gst_alsa_start_audio(this);
+    } else {
+        gst_alsa_set_params(this);
+    }
+}
+
+static void
+gst_alsa_get_property(GObject *object, guint prop_id, GValue *value, GParamSpec *pspec)
+{
+    GstAlsa *this;
+
+    this = (GstAlsa *)object;
+
+    switch (prop_id) {
+    case ARG_DEVICE:
+        g_value_set_string (value, this->device);
+        break;
+    case ARG_FORMAT:
+        g_value_set_int (value, this->format);
+        break;
+    case ARG_CHANNELS:
+        g_value_set_int (value, this->channels);
+        break;
+    case ARG_RATE:
+        g_value_set_int (value, this->rate);
+        break;
+    case ARG_PERIODCOUNT:
+        g_value_set_int (value, this->period_count);
+        break;
+    case ARG_PERIODFRAMES:
+        g_value_set_int (value, this->period_frames);
+        break;
+    default:
+        GST_DEBUG(0, "Unknown arg");
+        break;
+    }
+}
+
+static GstElementStateReturn
+gst_alsa_change_state(GstElement *element)
+{
+    GstAlsa *this;
+    guint chn;
+    
+    g_return_val_if_fail(element != NULL, FALSE);
+    this = GST_ALSA (element);
+    
+    switch (GST_STATE_PENDING(element)) {
+    case GST_STATE_NULL:
+        if (GST_FLAG_IS_SET(element, GST_ALSA_RUNNING))
+            gst_alsa_stop_audio((GstAlsa *)element);
+        if (GST_FLAG_IS_SET(element, GST_ALSA_OPEN))
+            gst_alsa_close_audio((GstAlsa *)element);
+        /* FIXME: clean up bytestreams, etc */
+        break;
+        
+    case GST_STATE_READY:
+        break;
+        
+    case GST_STATE_PAUSED:
+        if (GST_FLAG_IS_SET(element, GST_ALSA_OPEN) == FALSE)
+            if (gst_alsa_open_audio((GstAlsa *)element) == FALSE)
+                return GST_STATE_FAILURE;
+        if (GST_FLAG_IS_SET(element, GST_ALSA_RUNNING)) {
+            if (this->stream == SND_PCM_STREAM_PLAYBACK) {
+                for (chn = 0; chn < this->channels; chn++) {
+                    gst_alsa_sink_silence_on_channel (this, chn, this->avail);
+                }
+            }
+            gst_alsa_stop_audio((GstAlsa *)element);
+        }
+        break;
+        
+    case GST_STATE_PLAYING:
+        if (GST_FLAG_IS_SET(element, GST_ALSA_RUNNING) == FALSE)
+            if (gst_alsa_start_audio((GstAlsa *)element) == FALSE)
+                return GST_STATE_FAILURE;
+        break;
+    }
+    
+    if (GST_ELEMENT_CLASS(parent_class)->change_state)
+        return GST_ELEMENT_CLASS(parent_class)->change_state(element);
+
+    return GST_STATE_SUCCESS;
+}
+
+static gboolean
+gst_alsa_parse_caps (GstAlsa *this, GstCaps *caps)
+{
+    gint law, endianness, width, depth;
+    gboolean sign;
+    gint format = -1;
+    const gchar* format_name;
+
+    format_name = gst_caps_get_string(caps, "format");
+    
+    if (format_name == NULL) {
+        return FALSE;
+    } else if (strcmp(format_name, "int")==0) {
+        width = gst_caps_get_int (caps, "width");
+        depth = gst_caps_get_int (caps, "depth");
+        
+        law = gst_caps_get_int (caps, "law");
+        endianness = gst_caps_get_int (caps, "endianness");
+        sign = gst_caps_get_boolean (caps, "signed");
+        
+        if (law == 0) {
+            if (width == 8) {
+                if (sign == TRUE) {
+                    format = SND_PCM_FORMAT_S8;
+                } else {
+                    format = SND_PCM_FORMAT_U8;
+                }
+            } else if (width == 16) {
+                if (sign == TRUE) {
+                    if (endianness == G_LITTLE_ENDIAN)
+                        format = SND_PCM_FORMAT_S16_LE;
+                    else if (endianness == G_BIG_ENDIAN)
+                        format = SND_PCM_FORMAT_S16_BE;
+                } else {
+                    if (endianness == G_LITTLE_ENDIAN)
+                        format = SND_PCM_FORMAT_U16_LE;
+                    else if (endianness == G_BIG_ENDIAN)
+                        format = SND_PCM_FORMAT_U16_BE;
+                }
+            } else if (width == 24) {
+                if (sign == TRUE) {
+                    if (endianness == G_LITTLE_ENDIAN)
+                        format = SND_PCM_FORMAT_S24_LE;
+                    else if (endianness == G_BIG_ENDIAN)
+                        format = SND_PCM_FORMAT_S24_BE;
+                } else {
+                    if (endianness == G_LITTLE_ENDIAN)
+                        format = SND_PCM_FORMAT_U24_LE;
+                    else if (endianness == G_BIG_ENDIAN)
+                        format = SND_PCM_FORMAT_U24_BE;
+                }
+            } else if (width == 32) {
+                if (sign == TRUE) {
+                    if (endianness == G_LITTLE_ENDIAN)
+                        format = SND_PCM_FORMAT_S32_LE;
+                    else if (endianness == G_BIG_ENDIAN)
+                        format = SND_PCM_FORMAT_S32_BE;
+                } else {
+                    if (endianness == G_LITTLE_ENDIAN)
+                        format = SND_PCM_FORMAT_U32_LE;
+                    else if (endianness == G_BIG_ENDIAN)
+                        format = SND_PCM_FORMAT_U32_BE;
+                }
+            }
+        } else if (law == 1) { /* mu law */
+            if (width == depth && width == 8 && sign == FALSE) {
+                format = SND_PCM_FORMAT_MU_LAW;
+            } else {
+                return FALSE;
+            }
+        } else if (law == 2) { /* a law, ug. */
+            if (width == depth && width == 8 && sign == FALSE) {
+                format = SND_PCM_FORMAT_A_LAW;
+            }
+        } else {
+            return FALSE;
+        }
+    } else if (strcmp(format_name, "float")==0) {
+        if (strcmp(gst_caps_get_string(caps, "layout"), "gfloat")==0) {
+            format = SND_PCM_FORMAT_FLOAT;
+        } else {
+            return FALSE;
+            /* if you need float64, chat w/ me on irc.gstreamer.net and i'll tell you what needs to
+             * be done. i'm 'wingo'. */
+        }
+    } else {
+        return FALSE;
+    }
+    
+    this->format = format;
+    this->rate = gst_caps_get_int(caps, "rate");
+    if (this->data_interleaved)
+        this->channels = gst_caps_get_int(caps, "channels");
+    else if (gst_caps_get_int(caps, "channels") != 1)
+        return FALSE;
+    
+    return TRUE;
+}
+
+/* caps are so painful sometimes. */
+static GstCaps*
+gst_alsa_caps (GstAlsa *this)
+{
+    gint law, endianness, width, depth;
+    gboolean sign;
+    GstProps *props;
+    
+    g_return_val_if_fail (this != NULL && this->handle != NULL, NULL);
+    
+    if (this->format == SND_PCM_FORMAT_FLOAT) {
+        props = gst_props_new ("format", GST_PROPS_STRING ("float"),
+                               "layout", GST_PROPS_STRING ("gfloat"),
+                               "rate",       GST_PROPS_INT (this->rate),
+                               "channels",   GST_PROPS_INT ((this->data_interleaved ? this->channels : 1)),
+                               NULL);
+    } else {
+        // we'll just have to assume int, i don't feel like checking
+        if (this->format == SND_PCM_FORMAT_MU_LAW) {
+            law = 1;
+            width = 8;
+            sign = FALSE;
+            endianness = 0;
+        } else if (this->format == SND_PCM_FORMAT_A_LAW) {
+            law = 2;
+            width = 8;
+            sign = FALSE;
+            endianness = 0;
+        } else {
+            law = 0;
+            if (this->format == SND_PCM_FORMAT_S8) {
+                width = 8;
+                sign = TRUE;
+                endianness = 0;
+            } else if (this->format == SND_PCM_FORMAT_U8) {
+                width = 8;
+                sign = FALSE;
+                endianness = 0;
+            } else if (this->format == SND_PCM_FORMAT_S16_LE) {
+                width = 16;
+                sign = TRUE;
+                endianness = G_LITTLE_ENDIAN;
+            } else if (this->format == SND_PCM_FORMAT_S16_BE) {
+                width = 16;
+                sign = TRUE;
+                endianness = G_BIG_ENDIAN;
+            } else if (this->format == SND_PCM_FORMAT_U16_LE) {
+                width = 16;
+                sign = FALSE;
+                endianness = G_LITTLE_ENDIAN;
+            } else if (this->format == SND_PCM_FORMAT_U16_BE) {
+                width = 16;
+                sign = FALSE;
+                endianness = G_BIG_ENDIAN;
+            } else if (this->format == SND_PCM_FORMAT_S24_LE) {
+                width = 24;
+                sign = TRUE;
+                endianness = G_LITTLE_ENDIAN;
+            } else if (this->format == SND_PCM_FORMAT_S24_BE) {
+                width = 24;
+                sign = TRUE;
+                endianness = G_BIG_ENDIAN;
+            } else if (this->format == SND_PCM_FORMAT_U24_LE) {
+                width = 24;
+                sign = FALSE;
+                endianness = G_LITTLE_ENDIAN;
+            } else if (this->format == SND_PCM_FORMAT_U24_BE) {
+                width = 24;
+                sign = FALSE;
+                endianness = G_BIG_ENDIAN;
+            } else if (this->format == SND_PCM_FORMAT_S32_LE) {
+                width = 32;
+                sign = TRUE;
+                endianness = G_LITTLE_ENDIAN;
+            } else if (this->format == SND_PCM_FORMAT_S32_BE) {
+                width = 32;
+                sign = TRUE;
+                endianness = G_BIG_ENDIAN;
+            } else if (this->format == SND_PCM_FORMAT_U32_LE) {
+                width = 32;
+                sign = FALSE;
+                endianness = G_LITTLE_ENDIAN;
+            } else if (this->format == SND_PCM_FORMAT_U32_BE) {
+                width = 32;
+                sign = FALSE;
+                endianness = G_BIG_ENDIAN;
+            } else {
+                g_error ("what is going on here?");
+                return NULL;
+            }
+        }
+        depth = width;
+        props = gst_props_new ("format", GST_PROPS_STRING ("int"),
+                               "rate",       GST_PROPS_INT (this->rate),
+                               "channels",   GST_PROPS_INT ((this->data_interleaved ? this->channels : 1)),
+                               "law",        GST_PROPS_INT (law),
+                               "endianness", GST_PROPS_INT (endianness),
+                               "signed",     GST_PROPS_BOOLEAN (sign),
+                               "width",      GST_PROPS_INT (width),
+                               "depth",      GST_PROPS_INT (depth),
+                               NULL);
+    }
+    
+    return gst_caps_new ("alsasrc", "audio/raw", props);
+}
+
+/*
+ * Negotiates the caps, "borrowed" from gstosssink.c
+ */
+GstPadNegotiateReturn
+gst_alsa_negotiate(GstPad *pad, GstCaps **caps, gpointer *user_data)
+{
+    GstAlsa *this;
+    gboolean need_mmap;
+    
+    g_return_val_if_fail (pad != NULL, GST_PAD_NEGOTIATE_FAIL);
+    g_return_val_if_fail (GST_IS_PAD (pad), GST_PAD_NEGOTIATE_FAIL);
+    
+    this = GST_ALSA(gst_pad_get_parent(pad));
+    
+    // we decide
+    if (user_data == NULL) {
+        *caps = NULL;
+        return GST_PAD_NEGOTIATE_TRY;
+    }
+    // have we got caps?
+    else if (*caps) {
+        if (this->handle == NULL)
+            return GST_PAD_NEGOTIATE_FAIL;
+        
+        if (gst_alsa_parse_caps(this, *caps)) {
+            need_mmap = this->mmap_open;
+            
+            /* sync the params */
+            if (GST_FLAG_IS_SET(this, GST_ALSA_RUNNING))
+                gst_alsa_stop_audio(this);
+            
+            if (GST_FLAG_IS_SET(this, GST_ALSA_OPEN))
+                gst_alsa_close_audio(this);
+            
+            // FIXME send out another caps if nego fails
+            
+            if (!gst_alsa_open_audio(this))
+                return GST_PAD_NEGOTIATE_FAIL;
+            
+            if (!gst_alsa_start_audio(this))
+                return GST_PAD_NEGOTIATE_FAIL;
+            
+            if (need_mmap && !gst_alsa_get_channel_addresses(this))
+                return GST_PAD_NEGOTIATE_FAIL;
+            
+            return GST_PAD_NEGOTIATE_AGREE;
+        }
+        
+        return GST_PAD_NEGOTIATE_FAIL;
+    }
+    
+    return GST_PAD_NEGOTIATE_FAIL;
+}
+
+/* shamelessly stolen from pbd's audioengine. thanks, paul! */
+static void
+gst_alsa_loop (GstElement *element)
+{
+    struct pollfd pfd;
+    gboolean xrun_detected;
+    guint32 i;
+    GstAlsa *this = GST_ALSA(element);
+    
+    g_return_if_fail(this != NULL);
+    
+    snd_pcm_poll_descriptors (this->handle, &pfd, 1);
+    
+    if (this->stream == SND_PCM_STREAM_PLAYBACK) {
+        pfd.events = POLLOUT | POLLERR;
+    } else {
+        pfd.events = POLLIN | POLLERR;
+    }
+    
+    do {
+        if (poll (&pfd, 1, 1000) < 0) {
+            if (errno == EINTR) {
+                /* this happens mostly when run
+                 * under gdb, or when exiting due to a signal */
+                g_print ("EINTR\n");
+                continue;
+            }
+            
+            g_warning("poll call failed (%s)", strerror(errno));
+            return;
+        }
+        
+        if (pfd.revents & POLLERR) {
+            g_warning("alsa: poll reports error.");
+            return;
+        }
+        
+        if (pfd.revents == 0) {
+            g_print ("poll on alsa %s device \"%s\" timed out\n",
+                     this->stream==SND_PCM_STREAM_CAPTURE ? "capture" : "playback",
+                     this->device);
+            /* timed out, such as when the device is paused */
+            continue;
+        }
+        
+        xrun_detected = FALSE;
+        
+        this->avail = snd_pcm_avail_update (this->handle);
+//        g_print ("snd_pcm_avail_update() = %d\n", this->avail);
+        
+        if (this->avail < 0) {
+            if (this->avail == -EPIPE) {
+                xrun_detected = TRUE;
+            } else {
+                g_warning("unknown ALSA avail_update return value (%d)",
+                          (int)this->avail);
+                return;
+            }
+        }
+        
+        /* pretty sophisticated eh? */
+        if (xrun_detected)
+            g_warning ("xrun detected"); 
+        
+        /* we need to loop here because the available bytes might not be
+         * contiguous */
+        while (this->avail) {
+            /* changes this->avail, as a side effect */
+            if (!gst_alsa_get_channel_addresses (this) < 0) {
+                g_error("could not get channels");
+                return;
+            }
+            
+            if (this->mute && this->stream == SND_PCM_STREAM_PLAYBACK) {
+                for (i = 0; i < this->channels; i++) {
+                    if (this->mute & (1<<i)) {
+                        gst_alsa_sink_silence_on_channel (this, i, this->buffer_frames);
+                    }
+                }
+            }
+            
+            if (!this->process(this, this->avail)) {
+                g_warning("alsa: something happened while processing audio");
+                return;
+            }
+            
+            /* we could have released the mmap regions on a state change */
+            if (this->mmap_open)
+                gst_alsa_release_channel_addresses(this);
+        }
+       gst_element_yield (element);
+    } while (TRUE);
+}
+
+static gboolean
+gst_alsa_src_process (GstAlsa *this, snd_pcm_uframes_t frames)
+{
+    GstBuffer *buf;
+    GList *l;
+    GstAlsaPad *pad = NULL;
+    GstCaps *caps;
+    gint unit;
+//    gint i=0;
+    
+    static gboolean caps_set = FALSE;
+    
+    if (!caps_set) {
+        /* let's get on the caps-setting merry-go-round! */
+        caps = gst_alsa_caps(this);
+        l = this->pads;
+        while (l) {
+            if (!gst_pad_set_caps (GST_ALSA_PAD(l)->pad, caps)) {
+                g_print ("DANGER WILL ROBINSON!\n");
+                sleep(1);
+                return FALSE;
+            }
+            
+            l = l->next;
+        }
+        caps_set = TRUE;
+    }
+    
+    unit = this->sample_bytes * (this->data_interleaved ? this->channels : 1);
+    
+    while (frames) {
+//        g_print ("(%d) frames to process: %d\n", i++, frames);
+        l = this->pads;
+        while (l) {
+            pad = GST_ALSA_PAD(l);
+            
+            if (!pad->buf) {
+                pad->buf = g_malloc(this->period_frames * unit);
+                //  g_print ("created buffer %p of size %d\n", pad->buf, this->period_frames * unit);
+            }
+            /*
+            g_print ("pad->buf = %p, offset = %d\n", pad->buf, pad->offset);
+            g_print ("about to memcpy(%p, %p, %d)\n", 
+                     pad->buf + pad->offset * unit,
+                     pad->access_addr,  
+                     MIN(frames, this->period_frames - pad->offset) * unit);
+            */
+            memcpy(pad->buf + pad->offset * unit,
+                   pad->access_addr, 
+                   MIN(frames, this->period_frames - pad->offset) * unit);
+            
+            pad->offset += MIN(frames, this->period_frames - pad->offset);
+            
+            if (pad->offset >= this->period_frames) {
+                if (pad->offset > this->period_frames)
+                    G_BREAKPOINT();
+                
+                buf = gst_buffer_new();
+                GST_BUFFER_DATA(buf)    = pad->buf;
+                GST_BUFFER_SIZE(buf)    = this->period_frames * unit;
+                GST_BUFFER_MAXSIZE(buf) = this->period_frames * unit;
+                gst_pad_push(pad->pad, buf);
+                pad->buf = NULL;
+                pad->offset = 0;
+            }
+            l = l->next;
+        }
+        frames -= MIN(frames, this->period_frames - pad->offset); // shouldn't
+        // matter which pad, in theory (tm)
+    }
+    
+    return TRUE;
+}
+
+static gboolean
+gst_alsa_sink_process (GstAlsa *this, snd_pcm_uframes_t frames)
+{
+    guint8 *peeked;
+    guint32 len, avail;
+    GstEvent *event = NULL;
+    GList *l;
+    
+    /* this is necessary because the sample_bytes will change, probably, when
+     * caps are set, which will occur after the first bytestream_peek. we
+     * underestimate the amount of data we will need by peeking 'frames' only.
+     * */
+    
+    if (!this->sample_bytes) {
+        if (!GST_ALSA_PAD(this->pads)->bs)
+            GST_ALSA_PAD(this->pads)->bs = gst_bytestream_new(GST_ALSA_PAD(this->pads)->pad);
+        
+        if (!(peeked = gst_bytestream_peek_bytes(GST_ALSA_PAD(this->pads)->bs, frames))) {
+            g_warning("initial pull on pad %s returned NULL", GST_OBJECT_NAME(GST_ALSA_PAD(this->pads)->pad));
+            gst_element_set_state(GST_ELEMENT(this), GST_STATE_PAUSED);
+            return FALSE;
+        }
+        
+        if (!this->sample_bytes) {
+            g_critical ("alsa plugin requires a pipeline that can adequately set caps.");
+            return FALSE;
+        }
+    }
+    
+    len = frames * this->channels * this->sample_bytes;
+    
+    l = this->pads;
+    while (l) {
+        if (!GST_ALSA_PAD(this->pads)->bs)
+            GST_ALSA_PAD(this->pads)->bs = gst_bytestream_new(GST_ALSA_PAD(this->pads)->pad);
+        
+        if (!(peeked = gst_bytestream_peek_bytes(GST_ALSA_PAD(this->pads)->bs, len))) {
+            gst_bytestream_get_status(GST_ALSA_PAD(this->pads)->bs, &avail, &event);
+            if (event) {
+                g_warning("got an event on alsasink");
+                if (GST_EVENT_TYPE(event) == GST_EVENT_EOS) {
+                    /* really, we should just cut this pad out of the graph. let
+                     * me know when this is needed ;)
+                     * also, for sample accuracy etc, we should play avail
+                     * bytes, but hey. */
+                    gst_element_set_state(GST_ELEMENT(this), GST_STATE_PAUSED);
+                    gst_event_free(event);
+                    return TRUE;
+                }
+            } else {
+                /* the element at the top of the chain did not emit an eos
+                 * event. this is a Bug(tm) */
+                g_assert_not_reached();
+            }
+        }
+        
+        memcpy(GST_ALSA_PAD(this->pads)->access_addr, peeked, len);
+        gst_bytestream_flush(GST_ALSA_PAD(this->pads)->bs, len);
+        
+        l=l->next;
+    }
+    
+    return TRUE;
+}
+
+/* taken more or less from pbd's audioengine code */
+static gboolean
+gst_alsa_set_params (GstAlsa *this)
+{
+    snd_pcm_sw_params_t *sw_param;
+    snd_pcm_hw_params_t *hw_param;
+    snd_pcm_access_mask_t *mask;
+    gint ret;
+    
+    g_return_val_if_fail(this != NULL, FALSE);
+    g_return_val_if_fail(this->handle != NULL, FALSE);
+    
+    g_print("Preparing channel: %s %dHz, %d channels\n", 
+            snd_pcm_format_name(this->format), 
+            this->rate, this->channels);
+        
+    snd_pcm_hw_params_alloca(&hw_param);
+    snd_pcm_sw_params_alloca(&sw_param);
+        
+    ret = snd_pcm_hw_params_any(this->handle, hw_param);
+    if (ret < 0) {
+        g_warning("Broken configuration for this PCM: no configurations available");
+        return FALSE;
+    }
+    
+    if ((ret = snd_pcm_hw_params_set_periods_integer (this->handle, hw_param)) < 0) {
+        g_warning("cannot restrict period size to integral value.");
+        return FALSE;
+    }
+
+    mask = alloca(snd_pcm_access_mask_sizeof());
+    snd_pcm_access_mask_none(mask);
+    
+    if (this->data_interleaved)
+        snd_pcm_access_mask_set(mask, SND_PCM_ACCESS_MMAP_INTERLEAVED);
+    
+    snd_pcm_access_mask_set(mask, SND_PCM_ACCESS_MMAP_NONINTERLEAVED);
+    ret = snd_pcm_hw_params_set_access_mask(this->handle, hw_param, mask);
+    if (ret < 0) {
+        g_warning("the gstreamer alsa plugin does not support your hardware.");
+        return FALSE;
+    }
+    
+    if (this->format != SND_PCM_FORMAT_UNKNOWN) {
+        ret = snd_pcm_hw_params_set_format(this->handle, hw_param, this->format);
+        if (ret < 0) {
+            g_warning("Sample format (%s) not available: %s", snd_pcm_format_name(this->format), snd_strerror(ret));
+            return FALSE;
+        }
+        this->sample_bytes = snd_pcm_format_physical_width(this->format) / 8;
+    }
+    
+    ret = snd_pcm_hw_params_set_channels(this->handle, hw_param, this->channels);
+    if (ret < 0) {
+        g_warning("Channels count (%d) not available: %s", this->channels, snd_strerror(ret));
+        return FALSE;
+    }
+    this->channels = snd_pcm_hw_params_get_channels(hw_param);
+    
+    if (this->rate) {
+        ret = snd_pcm_hw_params_set_rate(this->handle, hw_param, this->rate, 0);
+        if (ret < 0) {
+            g_warning("error setting rate (%d): %s", this->rate, snd_strerror(ret));
+            return FALSE;
+        }
+    }
+    
+    if (this->period_count) {
+        ret = snd_pcm_hw_params_set_periods (this->handle, hw_param, this->period_count, 0);
+        if (ret < 0) {
+            g_warning("error setting period count minimum (%d): %s", this->period_count, snd_strerror(ret));
+            return FALSE;
+        }
+    }
+    
+    if (this->period_frames) {
+        ret = snd_pcm_hw_params_set_period_size (this->handle, hw_param, this->period_frames, 0);
+        if (ret < 0) {
+            g_warning("error setting period in frames (%d): %s", this->period_frames, snd_strerror(ret));
+            return FALSE;
+        }
+    }
+    
+    if (this->buffer_frames) {
+        ret = snd_pcm_hw_params_set_buffer_size (this->handle, hw_param, this->buffer_frames);
+        if (ret < 0) {
+            g_warning("error setting buffer size (%d): %s", this->buffer_frames, snd_strerror(ret));
+            return FALSE;
+        }
+    }
+    
+    ret = snd_pcm_hw_params(this->handle, hw_param);
+    if (ret < 0) {
+        g_warning("could not set hw params: %s", snd_strerror(ret));
+        snd_pcm_hw_params_dump(hw_param, this->out);
+        return FALSE;
+    }
+    
+    if (!this->rate)
+        this->rate = snd_pcm_hw_params_get_rate(hw_param, 0);
+    if (!this->format)
+        this->format = snd_pcm_hw_params_get_format(hw_param);
+    if (!this->period_count)
+        this->period_count = snd_pcm_hw_params_get_periods(hw_param, 0);
+    if (!this->period_frames)
+        this->period_frames = snd_pcm_hw_params_get_period_size(hw_param, 0);
+    if (!this->buffer_frames)
+        this->buffer_frames = snd_pcm_hw_params_get_buffer_size(hw_param);
+    if (this->buffer_frames != this->period_count * this->period_frames)
+        g_critical ("buffer size != period size * number of periods, unexpected things may happen!");
+    
+    snd_pcm_sw_params_current (this->handle, sw_param);
+
+    ret = snd_pcm_sw_params_set_start_threshold (this->handle, sw_param, ~0U);
+    if (ret < 0) {
+        g_warning("could not set start mode: %s", snd_strerror(ret));
+        return FALSE;
+    }
+    
+    ret = snd_pcm_sw_params_set_stop_threshold (this->handle, sw_param, ~0U);
+    if (ret < 0) {
+        g_warning("could not set stop mode: %s", snd_strerror(ret));
+        return FALSE;
+    }
+    
+    ret = snd_pcm_sw_params_set_silence_threshold (this->handle, sw_param, 0);
+    if (ret < 0) {
+        g_warning("could not set silence threshold: %s", snd_strerror(ret));
+        return FALSE;
+    }
+    
+    ret = snd_pcm_sw_params_set_silence_size (this->handle, sw_param, this->buffer_frames);
+    if (ret < 0) {
+        g_warning("could not set silence size: %s", snd_strerror(ret));
+        return FALSE;
+    }
+    
+    ret = snd_pcm_sw_params_set_avail_min (this->handle, sw_param, this->period_frames);
+    if (ret < 0) {
+        g_warning("could not set avail min: %s", snd_strerror(ret));
+        return FALSE;
+    }
+    
+    ret = snd_pcm_sw_params (this->handle, sw_param);
+    if (ret < 0) {
+        g_warning("could not set sw_params: %s", snd_strerror(ret));
+        return FALSE;
+    }
+    
+    snd_pcm_dump(this->handle, this->out);
+    
+    this->access_interleaved = !(snd_pcm_hw_params_get_access (hw_param) ==
+                                 SND_PCM_ACCESS_MMAP_NONINTERLEAVED);
+    
+    if (this->access_interleaved) {
+        this->interleave_unit = this->sample_bytes;
+        this->interleave_skip = this->interleave_unit * this->channels;
+    } else {
+        this->interleave_unit = 0; /* not used */
+        this->interleave_skip = this->sample_bytes;
+    }
+    
+    if (this->access_addr)
+        g_free (this->access_addr);
+    this->access_addr = g_new0 (char*, this->channels);
+    
+    return TRUE;
+}
+
+static gboolean
+gst_alsa_open_audio(GstAlsa *this)
+{
+    gint ret;
+    g_assert(this != NULL);
+
+    if (this->handle)
+        gst_alsa_close_audio(this);
+    
+    g_print("Opening alsa device \"%s\" for %s...\n", this->device,
+            this->stream==SND_PCM_STREAM_PLAYBACK ? "playback" : "capture");
+    
+    ret = snd_output_stdio_attach(&this->out, stdout, 0);
+    if (ret < 0) {
+        g_print("error opening log output: %s", snd_strerror(ret));
+        return FALSE;
+    }
+    
+    /* blocking i/o */
+    if ((ret = snd_pcm_open(&this->handle, this->device, this->stream, 0))) {
+        g_print("error opening pcm device: %s", snd_strerror(ret));
+        return FALSE;
+    }
+    
+    if (gst_alsa_set_params(this) == FALSE) {
+        gst_alsa_close_audio(this);
+        return FALSE;
+    }
+    
+    GST_FLAG_SET(this, GST_ALSA_OPEN);
+    return TRUE;
+}
+
+
+static gboolean
+gst_alsa_start_audio(GstAlsa *this)
+{
+    gint err;
+    guint32 chn;
+    
+    g_return_val_if_fail(this != NULL, FALSE);
+    g_return_val_if_fail(this->handle != NULL, FALSE);
+    
+    if ((err = snd_pcm_prepare (this->handle)) < 0) {
+        g_warning("channel prepare failed: %s", snd_strerror (err));
+        return FALSE;
+    }
+        
+    this->avail = snd_pcm_avail_update (this->handle);
+    
+    if (this->stream == SND_PCM_STREAM_PLAYBACK &&
+        this->avail != this->buffer_frames) {
+        g_warning ("full buffer not available at start");
+        return FALSE;
+    }
+    
+    if (!gst_alsa_get_channel_addresses (this)) {
+        return FALSE;
+    }
+    
+    if (this->stream == SND_PCM_STREAM_PLAYBACK) {
+        for (chn = 0; chn < this->channels; chn++) {
+            gst_alsa_sink_silence_on_channel (this, chn, this->buffer_frames);
+        }
+    }
+    
+    gst_alsa_release_channel_addresses (this);
+    
+    if ((err = snd_pcm_start (this->handle)) < 0) {
+        g_warning("could not start audio: %s", snd_strerror (err));
+        return FALSE;
+    }
+    
+    GST_FLAG_SET(this, GST_ALSA_RUNNING);
+    return TRUE;
+}
+
+static void
+gst_alsa_stop_audio(GstAlsa *this)
+{
+    gint err;
+    g_assert(this != NULL);
+    
+    g_return_if_fail(this != NULL);
+    g_return_if_fail(this->handle != NULL);
+
+    if (this->mmap_open)
+        gst_alsa_release_channel_addresses (this);
+    
+    if (this->stream == SND_PCM_STREAM_PLAYBACK && 
+        (err = snd_pcm_drop (this->handle)) < 0) {
+        g_warning("channel flush failed: %s", snd_strerror (err));
+        return;
+    }
+    
+    GST_FLAG_UNSET(this, GST_ALSA_RUNNING);
+}
+
+static void
+gst_alsa_close_audio(GstAlsa *this)
+{
+//    gint err;
+    g_return_if_fail(this != NULL);
+    g_return_if_fail(this->handle != NULL);
+
+/*    if ((err = snd_pcm_drop (this->handle)) < 0) {
+        g_warning("channel flush for failed: %s", snd_strerror (err));
+        return;
+        } */
+    
+    snd_pcm_close(this->handle);
+    
+    this->handle = NULL;
+
+    GST_FLAG_UNSET(this, GST_ALSA_OPEN);
+}
+
+static gboolean
+gst_alsa_get_channel_addresses (GstAlsa *this)
+{
+    guint32 err, i;
+    const snd_pcm_channel_area_t *a;
+    GList *l;
+    
+    g_return_val_if_fail (this->mmap_open == FALSE, FALSE);
+    
+    if ((err = snd_pcm_mmap_begin (this->handle, &this->mmap_areas, &this->offset, &this->avail)) < 0) {
+        g_warning("gstalsa: mmap failed: %s", snd_strerror(err));
+        return FALSE;
+    }
+    
+    GST_DEBUG(0, "got %d mmap'd frames\n", (int)this->avail);
+    
+//    g_print ("snd_pcm_mmap_begin() sets avail = %d\n", this->avail);
+    
+    l = this->pads;
+    while (l) {
+        a = &this->mmap_areas[GST_ALSA_PAD(l)->channel > 0 ?
+                             GST_ALSA_PAD(l)->channel-1 : 0];
+        GST_ALSA_PAD(l)->access_addr = (char *) a->addr + ((a->first + a->step *
+                                                            this->offset) / 8);
+        l = l->next;
+    }
+    
+    for (i=0; i<this->channels; i++) {
+        a = &this->mmap_areas[i];
+        this->access_addr[i] = (char *) a->addr + ((a->first + a->step * this->offset) / 8);
+    }
+    
+    this->mmap_open = TRUE;
+    
+    return TRUE;
+}
+
+static void
+gst_alsa_release_channel_addresses (GstAlsa *this)
+{
+    guint32 err, i;
+    GList *l;
+    
+    g_return_if_fail (this->mmap_open == TRUE);
+    
+    GST_DEBUG(0, "releasing mmap'd data region: %d frames\n", (int)this->avail);
+    
+    if ((err = snd_pcm_mmap_commit (this->handle, this->offset, this->avail)) < 0) {
+        g_warning("gstalsa: mmap commit failed: %s", snd_strerror(err));
+        return;
+    }
+    
+    l = this->pads;
+    while (l) {
+        GST_ALSA_PAD(l)->access_addr = NULL;
+        l = l->next;
+    }
+    
+    for (i=0; i<this->channels; i++) {
+        this->access_addr[i] = NULL;
+    }
+    
+    this->mmap_open = FALSE;
+    this->avail=0;
+}
+
+static void 
+gst_alsa_sink_silence_on_channel (GstAlsa *this, guint32 chn, guint32 nframes) 
+{
+    if (this->access_interleaved) {
+        memset_interleave 
+            (this->access_addr[chn],
+             0, nframes * this->sample_bytes,
+             this->interleave_unit,
+             this->interleave_skip);
+    } else {
+        memset (this->access_addr[chn], 0, nframes * this->sample_bytes);
+    }
+//    mark_channel_done (chn);
+}
+
+/* taken directly from paul davis' memops.cc */
+static void
+memset_interleave (char *dst, char val, unsigned int bytes, 
+                   unsigned int unit_bytes, 
+                   unsigned int skip_bytes) 
+{
+    switch (unit_bytes) {
+    case 1:
+        while (bytes--) {
+            *dst = val;
+            dst += skip_bytes;
+        }
+        break;
+    case 2:
+        while (bytes) {
+            *((short *) dst) = (short) val;
+            dst += skip_bytes;
+            bytes -= 2;
+        }
+        break;
+    case 4:                
+        while (bytes) {
+            *((int *) dst) = (int) val;
+            dst += skip_bytes;
+            bytes -= 4;
+        }
+        break;
+    }
+}
+
+static gboolean
+plugin_init (GModule *module, GstPlugin *plugin)
+{
+    GstElementFactory *factory;
+    
+    if (!gst_library_load ("gstbytestream")) {
+        gst_info("alsa: could not load support library: 'gstbytestream'\n");
+        return FALSE;
+    }
+    
+    factory = gst_elementfactory_new ("alsasrc", GST_TYPE_ALSA_SRC, &gst_alsa_src_details);
+    g_return_val_if_fail (factory != NULL, FALSE);
+    gst_elementfactory_add_padtemplate (factory, gst_alsa_src_pad_factory());
+    gst_elementfactory_add_padtemplate (factory, gst_alsa_src_request_pad_factory());
+    gst_plugin_add_feature (plugin, GST_PLUGIN_FEATURE (factory));
+    
+    factory = gst_elementfactory_new ("alsasink", GST_TYPE_ALSA_SINK, &gst_alsa_sink_details);
+    g_return_val_if_fail (factory != NULL, FALSE);
+    gst_elementfactory_add_padtemplate (factory, gst_alsa_sink_pad_factory());
+    gst_elementfactory_add_padtemplate (factory, gst_alsa_sink_request_pad_factory());
+    gst_plugin_add_feature (plugin, GST_PLUGIN_FEATURE (factory));
+    
+    gst_plugin_set_longname(plugin, "ALSA plugin library");
+    
+    return TRUE;
+}
+
+GstPluginDesc plugin_desc = {
+    GST_VERSION_MAJOR,
+    GST_VERSION_MINOR,
+    "alsa",
+    plugin_init
+};
+
+
diff --git a/ext/alsa/gstalsa.h b/ext/alsa/gstalsa.h
new file mode 100644 (file)
index 0000000..4fdaaa6
--- /dev/null
@@ -0,0 +1,126 @@
+/*
+    Copyright (C) 2001 CodeFactory AB
+    Copyright (C) 2001 Thomas Nyberg <thomas@codefactory.se>
+    Copyright (C) 2001 Andy Wingo <apwingo@eos.ncsu.edu>
+                            
+    This library is free software; you can redistribute it and/or
+    modify it under the terms of the GNU Library General Public
+    License as published by the Free Software Foundation; either
+    version 2 of the License, or (at your option) any later version.
+
+    This library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+    Library General Public License for more details.
+
+    You should have received a copy of the GNU Library General Public
+    License along with this library; if not, write to the Free
+    Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#ifndef __GST_ALSA_H__
+#define __GST_ALSA_H__
+
+#include <sys/asoundlib.h>
+#include <gst/gst.h>
+#include <libs/bytestream/gstbytestream.h>
+#include <glib.h>
+
+#define GST_ALSA(obj) G_TYPE_CHECK_INSTANCE_CAST(obj, GST_TYPE_ALSA, GstAlsa)
+#define GST_ALSA_CLASS(klass) G_TYPE_CHECK_CLASS_CAST(klass, GST_TYPE_ALSA, GstAlsaClass)
+#define GST_IS_ALSA(obj) G_TYPE_CHECK_INSTANCE_TYPE(obj, GST_TYPE_ALSA)
+#define GST_IS_ALSA_CLASS(klass) G_TYPE_CHECK_CLASS_TYPE(klass, GST_TYPE_ALSA)
+#define GST_TYPE_ALSA gst_alsa_get_type()
+
+#define GST_ALSA_SINK(obj) G_TYPE_CHECK_INSTANCE_CAST(obj, GST_TYPE_ALSA_SINK, GstAlsa)
+#define GST_ALSA_SINK_CLASS(klass) G_TYPE_CHECK_CLASS_CAST(klass, GST_TYPE_ALSA_SINK, GstAlsaClass)
+#define GST_IS_ALSA_SINK(obj) G_TYPE_CHECK_INSTANCE_TYPE(obj, GST_TYPE_ALSA_SINK)
+#define GST_IS_ALSA_SINK_CLASS(klass) G_TYPE_CHECK_CLASS_TYPE(klass, GST_TYPE_ALSA_SINK)
+#define GST_TYPE_ALSA_SINK gst_alsa_sink_get_type()
+
+#define GST_ALSA_SRC(obj) G_TYPE_CHECK_INSTANCE_CAST(obj, GST_TYPE_ALSA_SRC, GstAlsa)
+#define GST_ALSA_SRC_CLASS(klass) G_TYPE_CHECK_CLASS_CAST(klass, GST_TYPE_ALSA_SRC, GstAlsaClass)
+#define GST_IS_ALSA_SRC(obj) G_TYPE_CHECK_INSTANCE_TYPE(obj, GST_TYPE_ALSA_SRC)
+#define GST_IS_ALSA_SRC_CLASS(klass) G_TYPE_CHECK_CLASS_TYPE(klass, GST_TYPE_ALSA_SRC)
+#define GST_TYPE_ALSA_SRC gst_alsa_src_get_type()
+
+#define GST_ALSA_PAD(obj) ((GstAlsaPad*)obj->data) /* obj is a GList */
+
+/* I would have preferred to avoid this variety of trickery, but without it i
+ * can't tell whether I'm a source or a sink upon creation. */
+
+typedef struct _GstAlsa GstAlsa;
+typedef struct _GstAlsaClass GstAlsaClass;
+typedef GstAlsa GstAlsaSink;
+typedef GstAlsaClass GstAlsaSinkClass;
+typedef GstAlsa GstAlsaSrc;
+typedef GstAlsaClass GstAlsaSrcClass;
+
+enum {
+    GST_ALSA_OPEN = GST_ELEMENT_FLAG_LAST,
+    GST_ALSA_RUNNING,
+    GST_ALSA_FLAG_LAST = GST_ELEMENT_FLAG_LAST + 3,
+};
+
+typedef gboolean (*GstAlsaProcessFunc) (GstAlsa *, snd_pcm_uframes_t frames);
+
+typedef struct {
+    gint channel;
+    GstPad *pad;
+    GstByteStream *bs;
+    /* pointer to where we can access mmap_areas */
+    char *access_addr;
+    char *buf;
+    /* how much of the buffer we have used */
+    snd_pcm_uframes_t offset;
+} GstAlsaPad;
+
+struct _GstAlsa {
+    GstElement parent;
+
+    /* list of GstAlsaPads */
+    GList *pads;
+    
+    gchar *device;
+    snd_pcm_stream_t stream;
+    
+    snd_pcm_t *handle;
+    snd_output_t *out;
+    
+    /* our mmap'd data areas */
+    gboolean mmap_open;
+    const snd_pcm_channel_area_t *mmap_areas;
+    char **access_addr;
+    snd_pcm_uframes_t offset;
+    snd_pcm_sframes_t avail;
+    
+    GstAlsaProcessFunc process;
+    
+    snd_pcm_format_t format;
+    guint rate;
+    gint channels;
+    guint32 mute; /* bitmask. */
+    
+    /* the gstreamer data */
+    gboolean data_interleaved;
+    
+    /* access to the hardware */
+    gboolean access_interleaved;
+    guint sample_bytes;
+    guint interleave_unit;
+    guint interleave_skip;
+    
+    guint buffer_frames;
+    guint period_count; /* 'number of fragments' in oss-speak */
+    guint period_frames;
+};
+
+struct _GstAlsaClass {
+    GstElementClass parent_class;
+};
+
+GType gst_alsa_get_type (void);
+GType gst_alsa_sink_get_type (void);
+GType gst_alsa_src_get_type (void);
+
+#endif /* __ALSA_H__ */