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#include "mpegaudiodata.h"
24
25
26static int mp3_header_decompress(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;
30    int sample_rate= avctx->sample_rate;
31    int sample_rate_index=0;
32    int lsf, mpeg25, bitrate_index, frame_size;
33
34    header = AV_RB32(buf);
35    if(ff_mpa_check_header(header) >= 0){
36        *poutbuf= (uint8_t *) buf;
37        *poutbuf_size= buf_size;
38
39        return 0;
40    }
41
42    if(avctx->extradata_size != 15 || strcmp(avctx->extradata, "FFCMP3 0.0")){
43        av_log(avctx, AV_LOG_ERROR, "Extradata invalid %d\n", avctx->extradata_size);
44        return -1;
45    }
46
47    header= AV_RB32(avctx->extradata+11) & MP3_MASK;
48
49    lsf     = sample_rate < (24000+32000)/2;
50    mpeg25  = sample_rate < (12000+16000)/2;
51    sample_rate_index= (header>>10)&3;
52    sample_rate= ff_mpa_freq_tab[sample_rate_index] >> (lsf + mpeg25); //in case sample rate is a little off
53
54    for(bitrate_index=2; bitrate_index<30; bitrate_index++){
55        frame_size = ff_mpa_bitrate_tab[lsf][2][bitrate_index>>1];
56        frame_size = (frame_size * 144000) / (sample_rate << lsf) + (bitrate_index&1);
57        if(frame_size == buf_size + 4)
58            break;
59        if(frame_size == buf_size + 6)
60            break;
61    }
62    if(bitrate_index == 30){
63        av_log(avctx, AV_LOG_ERROR, "Could not find bitrate_index.\n");
64        return -1;
65    }
66
67    header |= (bitrate_index&1)<<9;
68    header |= (bitrate_index>>1)<<12;
69    header |= (frame_size == buf_size + 4)<<16; //FIXME actually set a correct crc instead of 0
70
71    *poutbuf_size= frame_size;
72    *poutbuf= av_malloc(frame_size + FF_INPUT_BUFFER_PADDING_SIZE);
73    memcpy(*poutbuf + frame_size - buf_size, buf, buf_size + FF_INPUT_BUFFER_PADDING_SIZE);
74
75    if(avctx->channels==2){
76        uint8_t *p= *poutbuf + frame_size - buf_size;
77        if(lsf){
78            FFSWAP(int, p[1], p[2]);
79            header |= (p[1] & 0xC0)>>2;
80            p[1] &= 0x3F;
81        }else{
82            header |= p[1] & 0x30;
83            p[1] &= 0xCF;
84        }
85    }
86
87    AV_WB32(*poutbuf, header);
88
89    return 1;
90}
91
92AVBitStreamFilter mp3_header_decompress_bsf={
93    "mp3decomp",
94    0,
95    mp3_header_decompress,
96};
97