2 * Copyright (C) 1999 Erik Walthinsen <omega@cse.ogi.edu>
3 * PCM - A-Law conversion
4 * Copyright (C) 2000 by Abramo Bagnara <abramo@alsa-project.org>
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Library General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Library General Public License for more details.
16 * You should have received a copy of the GNU Library General Public
17 * License along with this library; if not, write to the
18 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 * Boston, MA 02111-1307, USA.
26 #include "alaw-encode.h"
28 extern GstPadTemplate *alawenc_src_template, *alawenc_sink_template;
30 /* elementfactory information */
31 static GstElementDetails alawenc_details = {
32 "PCM to A Law conversion",
33 "Codec/Encoder/Audio",
34 "Convert 16bit PCM to 8bit A law",
35 "Zaheer Merali <zaheer@bellworldwide.net>"
38 /* Stereo signals and args */
48 static void gst_alawenc_class_init (GstALawEncClass *klass);
49 static void gst_alawenc_base_init (GstALawEncClass *klass);
50 static void gst_alawenc_init (GstALawEnc *alawenc);
52 static void gst_alawenc_set_property (GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec);
53 static void gst_alawenc_get_property (GObject *object, guint prop_id, GValue *value, GParamSpec *pspec);
55 static void gst_alawenc_chain (GstPad *pad, GstData *_data);
58 * s16_to_alaw() - Convert a 16-bit linear PCM value to 8-bit A-law
60 * s16_to_alaw() accepts an 16-bit integer and encodes it as A-law data.
62 * Linear Input Code Compressed Code
63 * ------------------------ ---------------
64 * 0000000wxyza 000wxyz
65 * 0000001wxyza 001wxyz
66 * 000001wxyzab 010wxyz
67 * 00001wxyzabc 011wxyz
68 * 0001wxyzabcd 100wxyz
69 * 001wxyzabcde 101wxyz
70 * 01wxyzabcdef 110wxyz
71 * 1wxyzabcdefg 111wxyz
73 * For further information see John C. Bellamy's Digital Telephony, 1982,
74 * John Wiley & Sons, pps 98-111 and 472-476.
77 static inline gint val_seg(gint val)
94 static guint8 s16_to_alaw(gint pcm_val)
105 if (pcm_val > 0x7fff)
112 /* Convert the scaled magnitude to segment number. */
113 seg = val_seg(pcm_val);
114 aval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0x0f);
119 static GstElementClass *parent_class = NULL;
120 /*static guint gst_stereo_signals[LAST_SIGNAL] = { 0 }; */
122 static GstPadLinkReturn
123 alawenc_link (GstPad *pad, const GstCaps *caps)
127 GstStructure *structure;
130 GstALawEnc* alawenc = GST_ALAWENC (GST_OBJECT_PARENT (pad));
132 structure = gst_caps_get_structure (caps, 0);
134 ret = gst_structure_get_int (structure, "rate", &rate);
135 ret &= gst_structure_get_int (structure, "channels", &channels);
137 if (!ret) return GST_PAD_LINK_REFUSED;
139 tempcaps = gst_caps_new_simple ("audio/x-alaw",
140 "depth", G_TYPE_INT, 8,
141 "width", G_TYPE_INT, 8,
142 "signed", G_TYPE_BOOLEAN, FALSE,
143 "rate", G_TYPE_INT, rate,
144 "channels", G_TYPE_INT, channels,
147 return gst_pad_try_set_caps (alawenc->srcpad, tempcaps);
151 gst_alawenc_get_type(void) {
152 static GType alawenc_type = 0;
155 static const GTypeInfo alawenc_info = {
156 sizeof(GstALawEncClass),
157 (GBaseInitFunc)gst_alawenc_base_init,
159 (GClassInitFunc)gst_alawenc_class_init,
164 (GInstanceInitFunc)gst_alawenc_init,
166 alawenc_type = g_type_register_static(GST_TYPE_ELEMENT, "GstALawEnc", &alawenc_info, 0);
172 gst_alawenc_base_init (GstALawEncClass *klass)
174 GstElementClass *element_class = GST_ELEMENT_CLASS (klass);
176 gst_element_class_add_pad_template (element_class, alawenc_src_template);
177 gst_element_class_add_pad_template (element_class, alawenc_sink_template);
178 gst_element_class_set_details (element_class, &alawenc_details);
182 gst_alawenc_class_init (GstALawEncClass *klass)
184 GObjectClass *gobject_class;
185 GstElementClass *gstelement_class;
187 gobject_class = (GObjectClass*)klass;
188 gstelement_class = (GstElementClass*)klass;
190 parent_class = g_type_class_ref(GST_TYPE_ELEMENT);
192 gobject_class->set_property = gst_alawenc_set_property;
193 gobject_class->get_property = gst_alawenc_get_property;
197 gst_alawenc_init (GstALawEnc *alawenc)
199 alawenc->sinkpad = gst_pad_new_from_template(alawenc_sink_template,"sink");
200 alawenc->srcpad = gst_pad_new_from_template(alawenc_src_template,"src");
201 gst_pad_set_link_function (alawenc->sinkpad, alawenc_link);
203 gst_element_add_pad(GST_ELEMENT(alawenc),alawenc->sinkpad);
204 gst_pad_set_chain_function(alawenc->sinkpad,gst_alawenc_chain);
205 gst_element_add_pad(GST_ELEMENT(alawenc),alawenc->srcpad);
209 gst_alawenc_chain (GstPad *pad,GstData *_data)
211 GstBuffer *buf = GST_BUFFER (_data);
218 g_return_if_fail(pad != NULL);
219 g_return_if_fail(GST_IS_PAD(pad));
220 g_return_if_fail(buf != NULL);
222 alawenc = GST_ALAWENC(GST_OBJECT_PARENT (pad));
223 g_return_if_fail(alawenc != NULL);
224 g_return_if_fail(GST_IS_ALAWENC(alawenc));
226 linear_data = (gint16 *)GST_BUFFER_DATA(buf);
227 outbuf=gst_buffer_new();
228 GST_BUFFER_DATA(outbuf) = (gchar*)g_new(guint8,GST_BUFFER_SIZE(buf)/2);
229 GST_BUFFER_SIZE(outbuf) = GST_BUFFER_SIZE(buf)/2;
232 alaw_data = (guint8*)GST_BUFFER_DATA(outbuf);
233 for (i = 0; i < GST_BUFFER_SIZE(outbuf); i++) {
234 *alaw_data = s16_to_alaw (*linear_data);
238 gst_buffer_unref(buf);
239 gst_pad_push(alawenc->srcpad,GST_DATA (outbuf));
243 gst_alawenc_set_property (GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec)
247 /* it's not null if we got it, but it might not be ours */
248 g_return_if_fail(GST_IS_ALAWENC(object));
249 alawenc = GST_ALAWENC(object);
258 gst_alawenc_get_property (GObject *object, guint prop_id, GValue *value, GParamSpec *pspec)
262 /* it's not null if we got it, but it might not be ours */
263 g_return_if_fail(GST_IS_ALAWENC(object));
264 alawenc = GST_ALAWENC(object);
268 G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);