--- /dev/null
+/* GStreamer
+ * Copyright (C) 2014 Antonio Ospite <ao2@ao2.it>
+ *
+ * alsamidisrc.c: Source element for ALSA MIDI sequencer events
+ *
+ * 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., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+/**
+ * SECTION:element-alsamidisrc
+ * @see_also: #GstPushSrc
+ *
+ * The alsamidisrc element is an element that fetches ALSA MIDI sequencer
+ * events and makes them available to elements understanding
+ * audio/x-midi-events in their sink pads.
+ *
+ * It can be used to generate notes from a MIDI input device.
+ *
+ * <refsect2>
+ * <title>Example launch line</title>
+ * |[
+ * gst-launch-1.0 -v alsamidisrc ports=129:0 ! fluiddec ! audioconvert ! autoaudiosink
+ * ]| This pipeline will listen for events from the sequencer device at port 129:0,
+ * and generate notes using the fluiddec element.
+ *
+ * |[
+ * vkeybd & gst-launch-1.0 -v alsamidisrc ports=128:0 ! fluiddec ! audioconvert ! autoaudiosink
+ * ]| Use a software midi keyboard to play fluiddec.
+ * </refsect2>
+ */
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include "alsamidisrc.h"
+
+GST_DEBUG_CATEGORY_STATIC (gst_alsa_midi_src_debug);
+#define GST_CAT_DEFAULT gst_alsa_midi_src_debug
+
+/*
+ * The MIDI specification declares some status bytes undefined:
+ *
+ * - 0xF4 System common - Undefined (Reserved)
+ * - 0xF5 System common - Undefined (Reserved)
+ * - 0xF9 System real-time - Undefined (Reserved)
+ * - 0xFD System real-time - Undefined (Reserved)
+ *
+ * See: http://www.midi.org/techspecs/midimessages.php#2
+ *
+ * Some other documents define status 0xf9 as a tick message with a period of
+ * 10ms:
+ *
+ * - http://www.blitter.com/~russtopia/MIDI/~jglatt/tech/midispec/tick.htm
+ * - http://www.sequencer.de/synth/index.php/MIDI_Format#0xf9_-_MIDI_Tick
+ *
+ * Even if non-standard it looks like this convention is quite widespread.
+ *
+ * For instance Fluidsynth uses 0xF9 as a "midi tick" message:
+ * http://sourceforge.net/p/fluidsynth/code-git/ci/master/tree/fluidsynth/src/midi/fluid_midi.h#l62
+ *
+ * And then so does the midiparse element in order to be compatible with
+ * Fluidsynth and the fluiddec element.
+ *
+ * Do the same to behave like midiparse.
+ */
+#define MIDI_TICK 0xf9
+#define MIDI_TICK_PERIOD_MS 10
+
+/* Functions specific to the Alsa MIDI sequencer API */
+
+#define DEFAULT_BUFSIZE 65536
+#define DEFAULT_CLIENT_NAME "alsamidisrc"
+#define DEFAULT_POLL_TIMEOUT_MS (MIDI_TICK_PERIOD_MS / 2)
+
+static int
+init_seq (GstAlsaMidiSrc * alsamidisrc)
+{
+ int ret;
+
+ ret = snd_seq_open (&alsamidisrc->seq, "default", SND_SEQ_OPEN_DUPLEX, 0);
+ if (ret < 0) {
+ GST_ERROR_OBJECT (alsamidisrc, "Cannot open sequencer - %s",
+ snd_strerror (ret));
+ goto error;
+ }
+
+ ret = snd_seq_set_client_name (alsamidisrc->seq, DEFAULT_CLIENT_NAME);
+ if (ret < 0) {
+ GST_ERROR_OBJECT (alsamidisrc, "Cannot set client name - %s",
+ snd_strerror (ret));
+ goto error_seq_close;
+ }
+
+ return 0;
+
+error_seq_close:
+ snd_seq_close (alsamidisrc->seq);
+error:
+ return ret;
+}
+
+/* Parses one or more port addresses from the string */
+static int
+parse_ports (const char *arg, GstAlsaMidiSrc * alsamidisrc)
+{
+ gchar **ports_list;
+ guint i;
+ int ret = 0;
+
+ GST_DEBUG_OBJECT (alsamidisrc, "ports: %s", arg);
+
+ /*
+ * Assume that ports are separated by commas.
+ *
+ * Commas are used instead of spaces because those are valid in client
+ * names.
+ */
+ ports_list = g_strsplit (arg, ",", 0);
+
+ alsamidisrc->port_count = g_strv_length (ports_list);
+ alsamidisrc->seq_ports = g_try_new (snd_seq_addr_t, alsamidisrc->port_count);
+ if (!alsamidisrc->seq_ports) {
+ GST_ERROR_OBJECT (alsamidisrc, "Out of memory");
+ ret = -ENOMEM;
+ goto out_free_ports_list;
+ }
+
+ for (i = 0; i < alsamidisrc->port_count; i++) {
+ gchar *port_name = ports_list[i];
+
+ ret = snd_seq_parse_address (alsamidisrc->seq, &alsamidisrc->seq_ports[i],
+ port_name);
+ if (ret < 0) {
+ GST_ERROR_OBJECT (alsamidisrc, "Invalid port %s - %s", port_name,
+ snd_strerror (ret));
+ goto error_free_seq_ports;
+ }
+ }
+
+ goto out_free_ports_list;
+
+error_free_seq_ports:
+ g_free (alsamidisrc->seq_ports);
+out_free_ports_list:
+ g_strfreev (ports_list);
+ return ret;
+}
+
+static int
+create_port (GstAlsaMidiSrc * alsamidisrc)
+{
+ int ret;
+
+ ret = snd_seq_create_simple_port (alsamidisrc->seq, DEFAULT_CLIENT_NAME,
+ SND_SEQ_PORT_CAP_WRITE |
+ SND_SEQ_PORT_CAP_SUBS_WRITE,
+ SND_SEQ_PORT_TYPE_MIDI_GENERIC | SND_SEQ_PORT_TYPE_APPLICATION);
+ if (ret < 0)
+ GST_ERROR_OBJECT (alsamidisrc, "Cannot create port - %s",
+ snd_strerror (ret));
+
+ return ret;
+}
+
+static void
+connect_ports (GstAlsaMidiSrc * alsamidisrc)
+{
+ int i;
+ int ret;
+
+ for (i = 0; i < alsamidisrc->port_count; ++i) {
+ ret =
+ snd_seq_connect_from (alsamidisrc->seq, 0,
+ alsamidisrc->seq_ports[i].client, alsamidisrc->seq_ports[i].port);
+ if (ret < 0)
+ /* Issue a warning and try the other ports */
+ GST_WARNING_OBJECT (alsamidisrc, "Cannot connect from port %d:%d - %s",
+ alsamidisrc->seq_ports[i].client, alsamidisrc->seq_ports[i].port,
+ snd_strerror (ret));
+ }
+}
+
+/* GStreamer specific functions */
+
+static GstStaticPadTemplate srctemplate = GST_STATIC_PAD_TEMPLATE ("src",
+ GST_PAD_SRC,
+ GST_PAD_ALWAYS,
+ GST_STATIC_CAPS ("audio/x-midi-event"));
+
+#define DEFAULT_PORTS NULL
+
+enum
+{
+ PROP_0,
+ PROP_PORTS,
+ PROP_LAST,
+};
+
+#define _do_init \
+ GST_DEBUG_CATEGORY_INIT (gst_alsa_midi_src_debug, "alsamidisrc", 0, "alsamidisrc element");
+#define gst_alsa_midi_src_parent_class parent_class
+G_DEFINE_TYPE_WITH_CODE (GstAlsaMidiSrc, gst_alsa_midi_src, GST_TYPE_PUSH_SRC,
+ _do_init);
+
+static void gst_alsa_midi_src_set_property (GObject * object, guint prop_id,
+ const GValue * value, GParamSpec * pspec);
+static void gst_alsa_midi_src_get_property (GObject * object, guint prop_id,
+ GValue * value, GParamSpec * pspec);
+
+static gboolean gst_alsa_midi_src_start (GstBaseSrc * basesrc);
+static gboolean gst_alsa_midi_src_stop (GstBaseSrc * basesrc);
+
+static GstFlowReturn
+gst_alsa_midi_src_create (GstPushSrc * src, GstBuffer ** buf);
+
+static void
+gst_alsa_midi_src_class_init (GstAlsaMidiSrcClass * klass)
+{
+ GObjectClass *gobject_class;
+ GstElementClass *gstelement_class;
+ GstBaseSrcClass *gstbase_src_class;
+ GstPushSrcClass *gstpush_src_class;
+
+ gobject_class = G_OBJECT_CLASS (klass);
+ gstelement_class = GST_ELEMENT_CLASS (klass);
+ gstbase_src_class = GST_BASE_SRC_CLASS (klass);
+ gstpush_src_class = GST_PUSH_SRC_CLASS (klass);
+
+ gobject_class->set_property = gst_alsa_midi_src_set_property;
+ gobject_class->get_property = gst_alsa_midi_src_get_property;
+
+ g_object_class_install_property (gobject_class, PROP_PORTS,
+ g_param_spec_string ("ports", "Ports",
+ "Comma separated list of sequencer ports (e.g. client:port,...)",
+ DEFAULT_PORTS, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+
+ gst_element_class_set_static_metadata (gstelement_class,
+ "AlsaMidi Source",
+ "Source",
+ "Push ALSA MIDI sequencer events around", "Antonio Ospite <ao2@ao2.it>");
+ gst_element_class_add_pad_template (gstelement_class,
+ gst_static_pad_template_get (&srctemplate));
+
+ gstbase_src_class->start = GST_DEBUG_FUNCPTR (gst_alsa_midi_src_start);
+ gstbase_src_class->stop = GST_DEBUG_FUNCPTR (gst_alsa_midi_src_stop);
+ gstpush_src_class->create = GST_DEBUG_FUNCPTR (gst_alsa_midi_src_create);
+}
+
+static void
+gst_alsa_midi_src_init (GstAlsaMidiSrc * alsamidisrc)
+{
+ alsamidisrc->ports = DEFAULT_PORTS;
+
+ gst_base_src_set_format (GST_BASE_SRC (alsamidisrc), GST_FORMAT_TIME);
+ gst_base_src_set_live (GST_BASE_SRC (alsamidisrc), TRUE);
+}
+
+static void
+gst_alsa_midi_src_set_property (GObject * object, guint prop_id,
+ const GValue * value, GParamSpec * pspec)
+{
+ GstAlsaMidiSrc *src;
+
+ src = GST_ALSA_MIDI_SRC (object);
+
+ switch (prop_id) {
+ case PROP_PORTS:
+ g_free (src->ports);
+ src->ports = g_value_dup_string (value);
+ break;
+ default:
+ G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+ break;
+ }
+}
+
+static void
+gst_alsa_midi_src_get_property (GObject * object, guint prop_id, GValue * value,
+ GParamSpec * pspec)
+{
+ GstAlsaMidiSrc *src;
+
+ g_return_if_fail (GST_IS_ALSA_MIDI_SRC (object));
+
+ src = GST_ALSA_MIDI_SRC (object);
+
+ switch (prop_id) {
+ case PROP_PORTS:
+ g_value_set_string (value, src->ports);
+ break;
+ default:
+ G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+ break;
+ }
+}
+
+static GstBuffer *
+prepare_buffer (GstAlsaMidiSrc * alsamidisrc, gpointer data, guint size)
+{
+ GstClockTime time;
+ gpointer local_data;
+ GstBuffer *buffer;
+
+ buffer = gst_buffer_new ();
+
+ time = alsamidisrc->tick * MIDI_TICK_PERIOD_MS * GST_MSECOND;
+
+ GST_BUFFER_DTS (buffer) = time;
+ GST_BUFFER_PTS (buffer) = time;
+ GST_BUFFER_OFFSET (buffer) = time;
+ GST_BUFFER_DURATION (buffer) = MIDI_TICK_PERIOD_MS * GST_MSECOND;
+
+ local_data = g_memdup (data, size);
+
+ gst_buffer_append_memory (buffer,
+ gst_memory_new_wrapped (0, local_data, size, 0, size, local_data,
+ g_free));
+
+ GST_MEMDUMP_OBJECT (alsamidisrc, "MIDI data:", local_data, size);
+
+ alsamidisrc->tick += 1;
+
+ return buffer;
+}
+
+static void
+push_buffer (GstAlsaMidiSrc * alsamidisrc, gpointer data, guint size,
+ GstBufferList * buffer_list)
+{
+ gst_buffer_list_add (buffer_list, prepare_buffer (alsamidisrc, data, size));
+}
+
+static void
+push_tick_buffer (GstAlsaMidiSrc * alsamidisrc, GstBufferList * buffer_list)
+{
+ alsamidisrc->buffer[0] = MIDI_TICK;
+ push_buffer (alsamidisrc, alsamidisrc->buffer, 1, buffer_list);
+}
+
+static GstFlowReturn
+gst_alsa_midi_src_create (GstPushSrc * src, GstBuffer ** buf)
+{
+ GstAlsaMidiSrc *alsamidisrc;
+ GstBufferList *buffer_list;
+ long size_ev = 0;
+ int err;
+ int ret;
+ guint len;
+
+ alsamidisrc = GST_ALSA_MIDI_SRC (src);
+
+ buffer_list = gst_buffer_list_new ();
+
+ snd_seq_poll_descriptors (alsamidisrc->seq, alsamidisrc->pfds,
+ alsamidisrc->npfds, POLLIN);
+
+ /*
+ * The file descriptors are polled with a timeout _less_ than 10ms (the MIDI
+ * tick period) in order not to loose events because of possible overlaps
+ * with MIDI ticks.
+ *
+ * If the polling times out (no new events) then a MIDI-tick event gets
+ * generated in order to keep the pipeline alive and progressing.
+ *
+ * If new events are present, then they are decoded and queued in
+ * a buffer_list. One buffer per event will be queued, all with different
+ * timestamps (see the prepare_buffer() function); maybe this can be
+ * optimized but a as a proof-of-concept mechanism it works OK.
+ */
+ ret = poll (alsamidisrc->pfds, alsamidisrc->npfds, DEFAULT_POLL_TIMEOUT_MS);
+ if (ret < 0) {
+ GST_ERROR_OBJECT (alsamidisrc, "ERROR in poll: %s", strerror (errno));
+ } else if (ret == 0) {
+ push_tick_buffer (alsamidisrc, buffer_list);
+ } else {
+ /* There are events available */
+ do {
+ snd_seq_event_t *event;
+ err = snd_seq_event_input (alsamidisrc->seq, &event);
+ if (err < 0)
+ break; /* Processed all events */
+
+ if (event) {
+ size_ev =
+ snd_midi_event_decode (alsamidisrc->parser, alsamidisrc->buffer,
+ DEFAULT_BUFSIZE, event);
+ if (size_ev < 0) {
+ /* ENOENT indicates an event that is not a MIDI message, silently skip it */
+ if (-ENOENT == size_ev) {
+ GST_WARNING_OBJECT (alsamidisrc,
+ "Warning: Received non-MIDI message");
+ push_tick_buffer (alsamidisrc, buffer_list);
+ } else {
+ GST_ERROR_OBJECT (alsamidisrc,
+ "Error decoding event from ALSA to output: %s",
+ strerror (-size_ev));
+ goto error;
+ }
+ } else {
+ push_buffer (alsamidisrc, alsamidisrc->buffer, size_ev, buffer_list);
+ }
+ }
+ } while (err > 0);
+ }
+
+ len = gst_buffer_list_length (buffer_list);
+ if (len == 0)
+ goto error;
+
+ /* Pop the _last_ buffer in the list */
+ *buf = gst_buffer_copy (gst_buffer_list_get (buffer_list, len - 1));
+ gst_buffer_list_remove (buffer_list, len - 1, 1);
+ --len;
+
+ /*
+ * If there are no more buffers left, free the list, otherwise push all the
+ * _previous_ buffers left in the list.
+ *
+ * The one popped above will be pushed last when this function returns.
+ */
+ if (len == 0)
+ gst_buffer_list_unref (buffer_list);
+ else
+ gst_pad_push_list (GST_BASE_SRC (src)->srcpad, buffer_list);
+
+ return GST_FLOW_OK;
+
+error:
+ gst_buffer_list_unref (buffer_list);
+ return GST_FLOW_ERROR;
+}
+
+static gboolean
+gst_alsa_midi_src_start (GstBaseSrc * basesrc)
+{
+ GstAlsaMidiSrc *alsamidisrc;
+ int ret;
+
+ alsamidisrc = GST_ALSA_MIDI_SRC (basesrc);
+
+ alsamidisrc->tick = 0;
+ alsamidisrc->port_count = 0;
+
+ ret = init_seq (alsamidisrc);
+ if (ret < 0)
+ goto err;
+
+ if (alsamidisrc->ports) {
+ ret = parse_ports (alsamidisrc->ports, alsamidisrc);
+ if (ret < 0)
+ goto error_seq_close;
+ }
+
+ ret = create_port (alsamidisrc);
+ if (ret < 0)
+ goto error_free_seq_ports;
+
+ connect_ports (alsamidisrc);
+
+ ret = snd_seq_nonblock (alsamidisrc->seq, 1);
+ if (ret < 0) {
+ GST_ERROR_OBJECT (alsamidisrc, "Cannot set nonblock mode - %s",
+ snd_strerror (ret));
+ goto error_free_seq_ports;
+ }
+
+ snd_midi_event_new (DEFAULT_BUFSIZE, &alsamidisrc->parser);
+ snd_midi_event_init (alsamidisrc->parser);
+ snd_midi_event_reset_decode (alsamidisrc->parser);
+
+ snd_midi_event_no_status (alsamidisrc->parser, 1);
+
+ alsamidisrc->buffer = g_try_malloc (DEFAULT_BUFSIZE);
+ if (alsamidisrc->buffer == NULL)
+ goto error_free_parser;
+
+ alsamidisrc->npfds =
+ snd_seq_poll_descriptors_count (alsamidisrc->seq, POLLIN);
+ alsamidisrc->pfds =
+ g_try_malloc (sizeof (*alsamidisrc->pfds) * alsamidisrc->npfds);
+ if (alsamidisrc->pfds == NULL)
+ goto error_free_buffer;
+
+ return TRUE;
+
+error_free_buffer:
+ g_free (alsamidisrc->buffer);
+error_free_parser:
+ snd_midi_event_free (alsamidisrc->parser);
+error_free_seq_ports:
+ g_free (alsamidisrc->seq_ports);
+error_seq_close:
+ snd_seq_close (alsamidisrc->seq);
+err:
+ return FALSE;
+}
+
+static gboolean
+gst_alsa_midi_src_stop (GstBaseSrc * basesrc)
+{
+ GstAlsaMidiSrc *alsamidisrc;
+
+ alsamidisrc = GST_ALSA_MIDI_SRC (basesrc);
+
+ g_free (alsamidisrc->pfds);
+ g_free (alsamidisrc->buffer);
+ snd_midi_event_free (alsamidisrc->parser);
+ g_free (alsamidisrc->seq_ports);
+ snd_seq_close (alsamidisrc->seq);
+
+ return TRUE;
+}
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