146 lines
3.8 KiB
C
146 lines
3.8 KiB
C
/*
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* Interface to libgsm for gsm encoding/decoding
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* Copyright (c) 2005 Alban Bedel <albeu@free.fr>
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* Copyright (c) 2006, 2007 Michel Bardiaux <mbardiaux@mediaxim.be>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser 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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* FFmpeg 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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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file libgsm.c
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* Interface to libgsm for gsm encoding/decoding
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*/
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// The idiosyncrasies of GSM-in-WAV are explained at http://kbs.cs.tu-berlin.de/~jutta/toast.html
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#include "avcodec.h"
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#include <gsm.h>
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// gsm.h misses some essential constants
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#define GSM_BLOCK_SIZE 33
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#define GSM_MS_BLOCK_SIZE 65
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#define GSM_FRAME_SIZE 160
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static int libgsm_init(AVCodecContext *avctx) {
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if (avctx->channels > 1 || avctx->sample_rate != 8000 || avctx->bit_rate != 13000)
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return -1;
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avctx->priv_data = gsm_create();
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switch(avctx->codec_id) {
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case CODEC_ID_GSM:
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avctx->frame_size = GSM_FRAME_SIZE;
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avctx->block_align = GSM_BLOCK_SIZE;
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break;
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case CODEC_ID_GSM_MS: {
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int one = 1;
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gsm_option(avctx->priv_data, GSM_OPT_WAV49, &one);
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avctx->frame_size = 2*GSM_FRAME_SIZE;
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avctx->block_align = GSM_MS_BLOCK_SIZE;
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}
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}
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avctx->coded_frame= avcodec_alloc_frame();
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avctx->coded_frame->key_frame= 1;
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return 0;
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}
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static int libgsm_close(AVCodecContext *avctx) {
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gsm_destroy(avctx->priv_data);
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avctx->priv_data = NULL;
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return 0;
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}
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static int libgsm_encode_frame(AVCodecContext *avctx,
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unsigned char *frame, int buf_size, void *data) {
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// we need a full block
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if(buf_size < avctx->block_align) return 0;
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switch(avctx->codec_id) {
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case CODEC_ID_GSM:
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gsm_encode(avctx->priv_data,data,frame);
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break;
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case CODEC_ID_GSM_MS:
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gsm_encode(avctx->priv_data,data,frame);
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gsm_encode(avctx->priv_data,((short*)data)+GSM_FRAME_SIZE,frame+32);
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}
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return avctx->block_align;
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}
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AVCodec libgsm_encoder = {
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"libgsm",
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CODEC_TYPE_AUDIO,
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CODEC_ID_GSM,
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0,
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libgsm_init,
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libgsm_encode_frame,
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libgsm_close,
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};
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AVCodec libgsm_ms_encoder = {
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"libgsm_ms",
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CODEC_TYPE_AUDIO,
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CODEC_ID_GSM_MS,
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0,
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libgsm_init,
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libgsm_encode_frame,
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libgsm_close,
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};
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static int libgsm_decode_frame(AVCodecContext *avctx,
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void *data, int *data_size,
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uint8_t *buf, int buf_size) {
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if(buf_size < avctx->block_align) return 0;
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switch(avctx->codec_id) {
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case CODEC_ID_GSM:
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if(gsm_decode(avctx->priv_data,buf,data)) return -1;
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*data_size = GSM_FRAME_SIZE*sizeof(int16_t);
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break;
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case CODEC_ID_GSM_MS:
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if(gsm_decode(avctx->priv_data,buf,data) ||
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gsm_decode(avctx->priv_data,buf+33,((int16_t*)data)+GSM_FRAME_SIZE)) return -1;
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*data_size = GSM_FRAME_SIZE*sizeof(int16_t)*2;
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}
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return avctx->block_align;
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}
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AVCodec libgsm_decoder = {
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"libgsm",
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CODEC_TYPE_AUDIO,
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CODEC_ID_GSM,
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0,
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libgsm_init,
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NULL,
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libgsm_close,
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libgsm_decode_frame,
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};
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AVCodec libgsm_ms_decoder = {
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"libgsm_ms",
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CODEC_TYPE_AUDIO,
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CODEC_ID_GSM_MS,
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0,
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libgsm_init,
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NULL,
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libgsm_close,
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libgsm_decode_frame,
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};
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