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272 lines
7.1 KiB
C
272 lines
7.1 KiB
C
/* GStreamer
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* Copyright (C) 1999 Erik Walthinsen <omega@cse.ogi.edu>
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* PCM - A-Law conversion
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* Copyright (C) 2000 by Abramo Bagnara <abramo@alsa-project.org>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <gst/gst.h>
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#include "alaw-encode.h"
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extern GstPadTemplate *alawenc_src_template, *alawenc_sink_template;
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/* elementfactory information */
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static GstElementDetails alawenc_details = {
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"PCM to A Law conversion",
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"Codec/Encoder/Audio",
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"Convert 16bit PCM to 8bit A law",
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"Zaheer Merali <zaheer@bellworldwide.net>"
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};
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/* Stereo signals and args */
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enum {
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/* FILL ME */
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LAST_SIGNAL
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};
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enum {
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ARG_0
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};
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static void gst_alawenc_class_init (GstALawEncClass *klass);
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static void gst_alawenc_base_init (GstALawEncClass *klass);
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static void gst_alawenc_init (GstALawEnc *alawenc);
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static void gst_alawenc_set_property (GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec);
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static void gst_alawenc_get_property (GObject *object, guint prop_id, GValue *value, GParamSpec *pspec);
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static void gst_alawenc_chain (GstPad *pad, GstData *_data);
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/*
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* s16_to_alaw() - Convert a 16-bit linear PCM value to 8-bit A-law
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*
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* s16_to_alaw() accepts an 16-bit integer and encodes it as A-law data.
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*
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* Linear Input Code Compressed Code
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* ------------------------ ---------------
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* 0000000wxyza 000wxyz
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* 0000001wxyza 001wxyz
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* 000001wxyzab 010wxyz
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* 00001wxyzabc 011wxyz
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* 0001wxyzabcd 100wxyz
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* 001wxyzabcde 101wxyz
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* 01wxyzabcdef 110wxyz
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* 1wxyzabcdefg 111wxyz
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*
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* For further information see John C. Bellamy's Digital Telephony, 1982,
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* John Wiley & Sons, pps 98-111 and 472-476.
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*/
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static inline gint val_seg(gint val)
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{
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gint r = 1;
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val >>= 8;
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if (val & 0xf0) {
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val >>= 4;
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r += 4;
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}
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if (val & 0x0c) {
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val >>= 2;
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r += 2;
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}
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if (val & 0x02)
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r += 1;
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return r;
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}
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static guint8 s16_to_alaw(gint pcm_val)
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{
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gint seg;
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guint8 mask;
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guint8 aval;
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if (pcm_val >= 0) {
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mask = 0xD5;
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} else {
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mask = 0x55;
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pcm_val = -pcm_val;
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if (pcm_val > 0x7fff)
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pcm_val = 0x7fff;
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}
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if (pcm_val < 256)
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aval = pcm_val >> 4;
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else {
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/* Convert the scaled magnitude to segment number. */
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seg = val_seg(pcm_val);
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aval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0x0f);
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}
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return aval ^ mask;
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}
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static GstElementClass *parent_class = NULL;
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/*static guint gst_stereo_signals[LAST_SIGNAL] = { 0 }; */
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static GstPadLinkReturn
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alawenc_link (GstPad *pad, GstCaps *caps)
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{
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GstCaps* tempcaps;
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gint rate, channels;
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GstALawEnc* alawenc = GST_ALAWENC (GST_OBJECT_PARENT (pad));
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if (!GST_CAPS_IS_FIXED (caps))
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return GST_PAD_LINK_DELAYED;
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if (!gst_caps_get (caps, "rate", &rate,
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"channels", &channels,
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NULL))
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return GST_PAD_LINK_DELAYED;
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tempcaps = GST_CAPS_NEW (
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"alawenc_src_caps",
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"audio/x-alaw",
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"depth", GST_PROPS_INT (8),
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"width", GST_PROPS_INT (8),
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"signed", GST_PROPS_BOOLEAN (FALSE),
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"rate", GST_PROPS_INT (rate),
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"channels", GST_PROPS_INT (channels),
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NULL);
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return gst_pad_try_set_caps (alawenc->srcpad, tempcaps);
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}
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GType
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gst_alawenc_get_type(void) {
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static GType alawenc_type = 0;
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if (!alawenc_type) {
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static const GTypeInfo alawenc_info = {
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sizeof(GstALawEncClass),
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(GBaseInitFunc)gst_alawenc_base_init,
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NULL,
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(GClassInitFunc)gst_alawenc_class_init,
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NULL,
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NULL,
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sizeof(GstALawEnc),
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0,
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(GInstanceInitFunc)gst_alawenc_init,
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};
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alawenc_type = g_type_register_static(GST_TYPE_ELEMENT, "GstALawEnc", &alawenc_info, 0);
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}
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return alawenc_type;
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}
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static void
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gst_alawenc_base_init (GstALawEncClass *klass)
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{
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GstElementClass *element_class = GST_ELEMENT_CLASS (klass);
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gst_element_class_add_pad_template (element_class, alawenc_src_template);
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gst_element_class_add_pad_template (element_class, alawenc_sink_template);
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gst_element_class_set_details (element_class, &alawenc_details);
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}
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static void
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gst_alawenc_class_init (GstALawEncClass *klass)
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{
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GObjectClass *gobject_class;
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GstElementClass *gstelement_class;
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gobject_class = (GObjectClass*)klass;
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gstelement_class = (GstElementClass*)klass;
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parent_class = g_type_class_ref(GST_TYPE_ELEMENT);
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gobject_class->set_property = gst_alawenc_set_property;
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gobject_class->get_property = gst_alawenc_get_property;
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}
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static void
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gst_alawenc_init (GstALawEnc *alawenc)
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{
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alawenc->sinkpad = gst_pad_new_from_template(alawenc_sink_template,"sink");
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alawenc->srcpad = gst_pad_new_from_template(alawenc_src_template,"src");
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gst_pad_set_link_function (alawenc->sinkpad, alawenc_link);
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gst_element_add_pad(GST_ELEMENT(alawenc),alawenc->sinkpad);
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gst_pad_set_chain_function(alawenc->sinkpad,gst_alawenc_chain);
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gst_element_add_pad(GST_ELEMENT(alawenc),alawenc->srcpad);
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}
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static void
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gst_alawenc_chain (GstPad *pad,GstData *_data)
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{
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GstBuffer *buf = GST_BUFFER (_data);
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GstALawEnc *alawenc;
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gint16 *linear_data;
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guint8 *alaw_data;
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GstBuffer* outbuf;
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gint i;
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g_return_if_fail(pad != NULL);
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g_return_if_fail(GST_IS_PAD(pad));
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g_return_if_fail(buf != NULL);
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alawenc = GST_ALAWENC(GST_OBJECT_PARENT (pad));
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g_return_if_fail(alawenc != NULL);
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g_return_if_fail(GST_IS_ALAWENC(alawenc));
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linear_data = (gint16 *)GST_BUFFER_DATA(buf);
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outbuf=gst_buffer_new();
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GST_BUFFER_DATA(outbuf) = (gchar*)g_new(guint8,GST_BUFFER_SIZE(buf)/2);
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GST_BUFFER_SIZE(outbuf) = GST_BUFFER_SIZE(buf)/2;
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alaw_data = (guint8*)GST_BUFFER_DATA(outbuf);
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for (i = 0; i < GST_BUFFER_SIZE(outbuf); i++) {
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*alaw_data = s16_to_alaw (*linear_data);
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alaw_data++;
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linear_data++;
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}
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gst_buffer_unref(buf);
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gst_pad_push(alawenc->srcpad,GST_DATA (outbuf));
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}
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static void
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gst_alawenc_set_property (GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec)
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{
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GstALawEnc *alawenc;
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/* it's not null if we got it, but it might not be ours */
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g_return_if_fail(GST_IS_ALAWENC(object));
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alawenc = GST_ALAWENC(object);
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switch (prop_id) {
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default:
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break;
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}
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}
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static void
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gst_alawenc_get_property (GObject *object, guint prop_id, GValue *value, GParamSpec *pspec)
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{
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GstALawEnc *alawenc;
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/* it's not null if we got it, but it might not be ours */
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g_return_if_fail(GST_IS_ALAWENC(object));
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alawenc = GST_ALAWENC(object);
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switch (prop_id) {
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default:
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G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
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break;
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}
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}
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