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.
*/
#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_init (GstALawEnc *alawenc);
static void gst_alawenc_set_property (GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec);
static void gst_alawenc_get_property (GObject *object, guint prop_id, GValue *value, GParamSpec *pspec);
static void gst_alawenc_chain (GstPad *pad, GstBuffer *buf);
/*
* 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 GstPadLinkReturn
alawenc_link (GstPad *pad, GstCaps *caps)
{
GstCaps* tempcaps;
gint rate, channels;
GstALawEnc* alawenc = GST_ALAWENC (GST_OBJECT_PARENT (pad));
if (!GST_CAPS_IS_FIXED (caps))
return GST_PAD_LINK_DELAYED;
if (!gst_caps_get (caps, "rate", &rate,
"channels", &channels,
NULL))
return GST_PAD_LINK_DELAYED;
tempcaps = GST_CAPS_NEW (
"alawenc_src_caps",
"audio/x-alaw",
"depth", GST_PROPS_INT (8),
"width", GST_PROPS_INT (8),
"signed", GST_PROPS_BOOLEAN (FALSE),
"rate", GST_PROPS_INT (rate),
"channels", GST_PROPS_INT (channels),
NULL);
return gst_pad_try_set_caps (alawenc->srcpad, tempcaps);
}
GType
gst_alawenc_get_type(void) {
static GType alawenc_type = 0;
if (!alawenc_type) {
static const GTypeInfo alawenc_info = {
sizeof(GstALawEncClass), NULL,
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_class_init (GstALawEncClass *klass)
{
GObjectClass *gobject_class;
GstElementClass *gstelement_class;
gobject_class = (GObjectClass*)klass;
gstelement_class = (GstElementClass*)klass;
parent_class = g_type_class_ref(GST_TYPE_ELEMENT);
gobject_class->set_property = gst_alawenc_set_property;
gobject_class->get_property = gst_alawenc_get_property;
}
static void
gst_alawenc_init (GstALawEnc *alawenc)
{
alawenc->sinkpad = gst_pad_new_from_template(alawenc_sink_template,"sink");
alawenc->srcpad = gst_pad_new_from_template(alawenc_src_template,"src");
gst_pad_set_link_function (alawenc->sinkpad, alawenc_link);
gst_element_add_pad(GST_ELEMENT(alawenc),alawenc->sinkpad);
gst_pad_set_chain_function(alawenc->sinkpad,gst_alawenc_chain);
gst_element_add_pad(GST_ELEMENT(alawenc),alawenc->srcpad);
}
static void
gst_alawenc_chain (GstPad *pad,GstBuffer *buf)
{
GstALawEnc *alawenc;
gint16 *linear_data;
guint8 *alaw_data;
GstBuffer* outbuf;
gint i;
g_return_if_fail(pad != NULL);
g_return_if_fail(GST_IS_PAD(pad));
g_return_if_fail(buf != NULL);
alawenc = GST_ALAWENC(GST_OBJECT_PARENT (pad));
g_return_if_fail(alawenc != NULL);
g_return_if_fail(GST_IS_ALAWENC(alawenc));
linear_data = (gint16 *)GST_BUFFER_DATA(buf);
outbuf=gst_buffer_new();
GST_BUFFER_DATA(outbuf) = (gchar*)g_new(guint8,GST_BUFFER_SIZE(buf)/2);
GST_BUFFER_SIZE(outbuf) = GST_BUFFER_SIZE(buf)/2;
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(buf);
gst_pad_push(alawenc->srcpad,outbuf);
}
static void
gst_alawenc_set_property (GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec)
{
GstALawEnc *alawenc;
/* it's not null if we got it, but it might not be ours */
g_return_if_fail(GST_IS_ALAWENC(object));
alawenc = GST_ALAWENC(object);
switch (prop_id) {
default:
break;
}
}
static void
gst_alawenc_get_property (GObject *object, guint prop_id, GValue *value, GParamSpec *pspec)
{
GstALawEnc *alawenc;
/* it's not null if we got it, but it might not be ours */
g_return_if_fail(GST_IS_ALAWENC(object));
alawenc = GST_ALAWENC(object);
switch (prop_id) {
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
break;
}
}