libavcodec/mp3_header_compress_bsf.c

   1 /*
   2  * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
   3  *
   4  * This file is part of FFmpeg.
   5  *
   6  * FFmpeg is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * FFmpeg is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with FFmpeg; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #include "avcodec.h"
  22 #include "mpegaudio.h"
  23
  24
  25 static int mp3_header_compress(AVBitStreamFilterContext *bsfc, AVCodecContext *avctx, const char *args,
  26                      uint8_t **poutbuf, int *poutbuf_size,
  27                      const uint8_t *buf, int buf_size, int keyframe){
  28     uint32_t header, extraheader;
  29     int mode_extension, header_size;
  30
  31     if(avctx->strict_std_compliance > FF_COMPLIANCE_EXPERIMENTAL){
  32         av_log(avctx, AV_LOG_ERROR, "not standards compliant\n");
  33         return -1;
  34     }
  35
  36     header = AV_RB32(buf);
  37     mode_extension= (header>>4)&3;
  38
  39     if(ff_mpa_check_header(header) < 0 || (header&0x60000) != 0x20000){
  40 output_unchanged:
  41         *poutbuf= (uint8_t *) buf;
  42         *poutbuf_size= buf_size;
  43
  44         av_log(avctx, AV_LOG_INFO, "cannot compress %08X\n", header);
  45         return 0;
  46     }
  47
  48     if(avctx->extradata_size == 0){
  49         avctx->extradata_size=15;
  50         avctx->extradata= av_malloc(avctx->extradata_size);
  51         strcpy(avctx->extradata, "FFCMP3 0.0");
  52         memcpy(avctx->extradata+11, buf, 4);
  53     }
  54     if(avctx->extradata_size != 15){
  55         av_log(avctx, AV_LOG_ERROR, "Extradata invalid\n");
  56         return -1;
  57     }
  58     extraheader = AV_RB32(avctx->extradata+11);
  59     if((extraheader&MP3_MASK) != (header&MP3_MASK))
  60         goto output_unchanged;
  61
  62     header_size= (header&0x10000) ? 4 : 6;
  63
  64     *poutbuf_size= buf_size - header_size;
  65     *poutbuf= av_malloc(buf_size - header_size + FF_INPUT_BUFFER_PADDING_SIZE);
  66     memcpy(*poutbuf, buf + header_size, buf_size - header_size + FF_INPUT_BUFFER_PADDING_SIZE);
  67
  68     if(avctx->channels==2){
  69         if((header & (3<<19)) != 3<<19){
  70             (*poutbuf)[1] &= 0x3F;
  71             (*poutbuf)[1] |= mode_extension<<6;
  72             FFSWAP(int, (*poutbuf)[1], (*poutbuf)[2]);
  73         }else{
  74             (*poutbuf)[1] &= 0x8F;
  75             (*poutbuf)[1] |= mode_extension<<4;
  76         }
  77     }
  78
  79     return 1;
  80 }
  81
  82 AVBitStreamFilter mp3_header_compress_bsf={
  83     "mp3comp",
  84     0,
  85     mp3_header_compress,
  86 };