1/*
2 * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
3 *
4 * This file is part of Libav.
5 *
6 * Libav 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 * Libav 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 Libav; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21#include "libavutil/intreadwrite.h"
22#include "avcodec.h"
23#include "mpegaudiodecheader.h"
24
25
26static int mp3_header_compress(AVBitStreamFilterContext *bsfc, AVCodecContext *avctx, const char *args,
27                     uint8_t **poutbuf, int *poutbuf_size,
28                     const uint8_t *buf, int buf_size, int keyframe){
29    uint32_t header, extraheader;
30    int mode_extension, header_size;
31
32    if(avctx->strict_std_compliance > FF_COMPLIANCE_EXPERIMENTAL){
33        av_log(avctx, AV_LOG_ERROR, "not standards compliant\n");
34        return -1;
35    }
36
37    header = AV_RB32(buf);
38    mode_extension= (header>>4)&3;
39
40    if(ff_mpa_check_header(header) < 0 || (header&0x60000) != 0x20000){
41output_unchanged:
42        *poutbuf= (uint8_t *) buf;
43        *poutbuf_size= buf_size;
44
45        av_log(avctx, AV_LOG_INFO, "cannot compress %08X\n", header);
46        return 0;
47    }
48
49    if(avctx->extradata_size == 0){
50        avctx->extradata_size=15;
51        avctx->extradata= av_malloc(avctx->extradata_size);
52        strcpy(avctx->extradata, "FFCMP3 0.0");
53        memcpy(avctx->extradata+11, buf, 4);
54    }
55    if(avctx->extradata_size != 15){
56        av_log(avctx, AV_LOG_ERROR, "Extradata invalid\n");
57        return -1;
58    }
59    extraheader = AV_RB32(avctx->extradata+11);
60    if((extraheader&MP3_MASK) != (header&MP3_MASK))
61        goto output_unchanged;
62
63    header_size= (header&0x10000) ? 4 : 6;
64
65    *poutbuf_size= buf_size - header_size;
66    *poutbuf= av_malloc(buf_size - header_size + FF_INPUT_BUFFER_PADDING_SIZE);
67    memcpy(*poutbuf, buf + header_size, buf_size - header_size + FF_INPUT_BUFFER_PADDING_SIZE);
68
69    if(avctx->channels==2){
70        if((header & (3<<19)) != 3<<19){
71            (*poutbuf)[1] &= 0x3F;
72            (*poutbuf)[1] |= mode_extension<<6;
73            FFSWAP(int, (*poutbuf)[1], (*poutbuf)[2]);
74        }else{
75            (*poutbuf)[1] &= 0x8F;
76            (*poutbuf)[1] |= mode_extension<<4;
77        }
78    }
79
80    return 1;
81}
82
83AVBitStreamFilter ff_mp3_header_compress_bsf={
84    "mp3comp",
85    0,
86    mp3_header_compress,
87};
88