gstreamer/gst/law/alaw-encode.c

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/* GStreamer
* Copyright (C) 1999 Erik Walthinsen <omega@cse.ogi.edu>
* PCM - A-Law conversion
* Copyright (C) 2000 by Abramo Bagnara <abramo@alsa-project.org>
*
* 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 2.1 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., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <gst/gst.h>
#include "alaw-encode.h"
extern GstPadTemplate *alawenc_src_template, *alawenc_sink_template;
/* Stereo signals and args */
enum
{
/* FILL ME */
LAST_SIGNAL
};
enum
{
ARG_0
};
static void gst_alawenc_class_init (GstALawEncClass * klass);
static void gst_alawenc_base_init (GstALawEncClass * klass);
static void gst_alawenc_init (GstALawEnc * alawenc);
static GstFlowReturn gst_alawenc_chain (GstPad * pad, GstBuffer * buffer);
/*
* s16_to_alaw() - Convert a 16-bit linear PCM value to 8-bit A-law
*
* s16_to_alaw() accepts an 16-bit integer and encodes it as A-law data.
*
* Linear Input Code Compressed Code
* ------------------------ ---------------
* 0000000wxyza 000wxyz
* 0000001wxyza 001wxyz
* 000001wxyzab 010wxyz
* 00001wxyzabc 011wxyz
* 0001wxyzabcd 100wxyz
* 001wxyzabcde 101wxyz
* 01wxyzabcdef 110wxyz
* 1wxyzabcdefg 111wxyz
*
* For further information see John C. Bellamy's Digital Telephony, 1982,
* John Wiley & Sons, pps 98-111 and 472-476.
*/
static inline gint
val_seg (gint val)
{
gint r = 1;
val >>= 8;
if (val & 0xf0) {
val >>= 4;
r += 4;
}
if (val & 0x0c) {
val >>= 2;
r += 2;
}
if (val & 0x02)
r += 1;
return r;
}
static guint8
s16_to_alaw (gint pcm_val)
{
gint seg;
guint8 mask;
guint8 aval;
if (pcm_val >= 0) {
mask = 0xD5;
} else {
mask = 0x55;
pcm_val = -pcm_val;
if (pcm_val > 0x7fff)
pcm_val = 0x7fff;
}
if (pcm_val < 256)
aval = pcm_val >> 4;
else {
/* Convert the scaled magnitude to segment number. */
seg = val_seg (pcm_val);
aval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0x0f);
}
return aval ^ mask;
}
static GstElementClass *parent_class = NULL;
/*static guint gst_stereo_signals[LAST_SIGNAL] = { 0 }; */
static GstCaps *
alawenc_getcaps (GstPad * pad)
{
GstALawEnc *alawenc;
GstPad *otherpad;
GstCaps *base_caps, *othercaps, *result;
GstStructure *structure;
const GValue *rate, *chans;
alawenc = GST_ALAWENC (GST_PAD_PARENT (pad));
/* we can do what our template says */
base_caps = gst_caps_copy (gst_pad_get_pad_template_caps (pad));
if (pad == alawenc->srcpad) {
otherpad = alawenc->sinkpad;
} else {
otherpad = alawenc->srcpad;
}
othercaps = gst_pad_peer_get_caps (otherpad);
if (othercaps) {
GstStructure *structure;
const GValue *orate, *ochans;
const GValue *rate, *chans;
GValue irate = { 0 }, ichans = {
0};
structure = gst_caps_get_structure (othercaps, 0);
orate = gst_structure_get_value (structure, "rate");
ochans = gst_structure_get_value (structure, "channels");
if (!rate || !chans)
goto done;
structure = gst_caps_get_structure (base_caps, 0);
rate = gst_structure_get_value (structure, "rate");
chans = gst_structure_get_value (structure, "channels");
if (!rate || !chans)
goto done;
gst_value_intersect (&irate, orate, rate);
gst_value_intersect (&ichans, ochans, chans);
/* Set the samplerate/channels on the to-be-returned caps */
structure = gst_caps_get_structure (base_caps, 0);
gst_structure_set_value (structure, "rate", &irate);
gst_structure_set_value (structure, "channels", &ichans);
gst_caps_unref (othercaps);
}
done:
return base_caps;
}
static gboolean
alawenc_setcaps (GstPad * pad, GstCaps * caps)
{
GstALawEnc *alawenc;
GstPad *otherpad;
GstStructure *structure;
const GValue *rate, *chans;
GstCaps *base_caps;
alawenc = GST_ALAWENC (GST_PAD_PARENT (pad));
structure = gst_caps_get_structure (caps, 0);
rate = gst_structure_get_value (structure, "rate");
chans = gst_structure_get_value (structure, "channels");
if (!rate || !chans)
return FALSE;
if (pad == alawenc->sinkpad) {
otherpad = alawenc->srcpad;
} else {
otherpad = alawenc->sinkpad;
}
base_caps = gst_caps_copy (gst_pad_get_pad_template_caps (otherpad));
structure = gst_caps_get_structure (base_caps, 0);
gst_structure_set_value (structure, "rate", rate);
gst_structure_set_value (structure, "channels", chans);
gst_pad_set_caps (otherpad, base_caps);
gst_caps_unref (base_caps);
return TRUE;
}
GType
gst_alawenc_get_type (void)
{
static GType alawenc_type = 0;
if (!alawenc_type) {
static const GTypeInfo alawenc_info = {
sizeof (GstALawEncClass),
(GBaseInitFunc) gst_alawenc_base_init,
NULL,
(GClassInitFunc) gst_alawenc_class_init,
NULL,
NULL,
sizeof (GstALawEnc),
0,
(GInstanceInitFunc) gst_alawenc_init,
};
alawenc_type =
g_type_register_static (GST_TYPE_ELEMENT, "GstALawEnc", &alawenc_info,
0);
}
return alawenc_type;
}
static void
gst_alawenc_base_init (GstALawEncClass * klass)
{
GstElementClass *element_class = GST_ELEMENT_CLASS (klass);
GstElementDetails alawenc_details = {
"PCM to A Law conversion",
"Codec/Encoder/Audio",
"Convert 16bit PCM to 8bit A law",
"Zaheer Abbas Merali <zaheerabbas at merali dot org>"
};
gst_element_class_add_pad_template (element_class, alawenc_src_template);
gst_element_class_add_pad_template (element_class, alawenc_sink_template);
gst_element_class_set_details (element_class, &alawenc_details);
}
static void
gst_alawenc_class_init (GstALawEncClass * klass)
{
parent_class = g_type_class_ref (GST_TYPE_ELEMENT);
}
static void
gst_alawenc_init (GstALawEnc * alawenc)
{
alawenc->sinkpad = gst_pad_new_from_template (alawenc_sink_template, "sink");
gst_pad_set_setcaps_function (alawenc->sinkpad, alawenc_setcaps);
gst_pad_set_getcaps_function (alawenc->sinkpad, alawenc_getcaps);
gst_pad_set_chain_function (alawenc->sinkpad, gst_alawenc_chain);
gst_element_add_pad (GST_ELEMENT (alawenc), alawenc->sinkpad);
alawenc->srcpad = gst_pad_new_from_template (alawenc_src_template, "src");
gst_pad_set_setcaps_function (alawenc->srcpad, alawenc_setcaps);
gst_pad_set_getcaps_function (alawenc->srcpad, alawenc_getcaps);
gst_element_add_pad (GST_ELEMENT (alawenc), alawenc->srcpad);
}
static GstFlowReturn
gst_alawenc_chain (GstPad * pad, GstBuffer * buffer)
{
GstALawEnc *alawenc;
gint16 *linear_data;
guint8 *alaw_data;
GstBuffer *outbuf;
gint i;
alawenc = GST_ALAWENC (GST_OBJECT_PARENT (pad));
linear_data = (gint16 *) GST_BUFFER_DATA (buffer);
outbuf = gst_buffer_new_and_alloc (GST_BUFFER_SIZE (buffer) / 2);
GST_BUFFER_TIMESTAMP (outbuf) = GST_BUFFER_TIMESTAMP (buffer);
GST_BUFFER_DURATION (outbuf) = GST_BUFFER_DURATION (buffer);
gst_buffer_set_caps (outbuf, GST_PAD_CAPS (alawenc->srcpad));
alaw_data = (guint8 *) GST_BUFFER_DATA (outbuf);
for (i = 0; i < GST_BUFFER_SIZE (outbuf); i++) {
*alaw_data = s16_to_alaw (*linear_data);
alaw_data++;
linear_data++;
}
gst_buffer_unref (buffer);
return gst_pad_push (alawenc->srcpad, outbuf);
}