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ffmpeg / libavcodec / mp3_header_compress_bsf.c @ 2912e87a

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/*
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 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
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 *
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 * This file is part of Libav.
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 *
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 * Libav 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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 * Libav 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 Libav; 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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#include "avcodec.h"
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#include "mpegaudio.h"
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static int mp3_header_compress(AVBitStreamFilterContext *bsfc, AVCodecContext *avctx, const char *args,
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                     uint8_t **poutbuf, int *poutbuf_size,
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                     const uint8_t *buf, int buf_size, int keyframe){
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    uint32_t header, extraheader;
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    int mode_extension, header_size;
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    if(avctx->strict_std_compliance > FF_COMPLIANCE_EXPERIMENTAL){
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        av_log(avctx, AV_LOG_ERROR, "not standards compliant\n");
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        return -1;
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    }
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    header = AV_RB32(buf);
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    mode_extension= (header>>4)&3;
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    if(ff_mpa_check_header(header) < 0 || (header&0x60000) != 0x20000){
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output_unchanged:
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        *poutbuf= (uint8_t *) buf;
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        *poutbuf_size= buf_size;
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        av_log(avctx, AV_LOG_INFO, "cannot compress %08X\n", header);
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        return 0;
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    }
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    if(avctx->extradata_size == 0){
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        avctx->extradata_size=15;
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        avctx->extradata= av_malloc(avctx->extradata_size);
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        strcpy(avctx->extradata, "FFCMP3 0.0");
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        memcpy(avctx->extradata+11, buf, 4);
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    }
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    if(avctx->extradata_size != 15){
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        av_log(avctx, AV_LOG_ERROR, "Extradata invalid\n");
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        return -1;
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    }
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    extraheader = AV_RB32(avctx->extradata+11);
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    if((extraheader&MP3_MASK) != (header&MP3_MASK))
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        goto output_unchanged;
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    header_size= (header&0x10000) ? 4 : 6;
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    *poutbuf_size= buf_size - header_size;
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    *poutbuf= av_malloc(buf_size - header_size + FF_INPUT_BUFFER_PADDING_SIZE);
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    memcpy(*poutbuf, buf + header_size, buf_size - header_size + FF_INPUT_BUFFER_PADDING_SIZE);
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    if(avctx->channels==2){
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        if((header & (3<<19)) != 3<<19){
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            (*poutbuf)[1] &= 0x3F;
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            (*poutbuf)[1] |= mode_extension<<6;
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            FFSWAP(int, (*poutbuf)[1], (*poutbuf)[2]);
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        }else{
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            (*poutbuf)[1] &= 0x8F;
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            (*poutbuf)[1] |= mode_extension<<4;
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        }
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    }
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    return 1;
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}
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AVBitStreamFilter ff_mp3_header_compress_bsf={
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    "mp3comp",
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    0,
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    mp3_header_compress,
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};