libavcodec/mpegaudio_parser.c

   1 /*
   2  * MPEG Audio parser
   3  * Copyright (c) 2003 Fabrice Bellard
   4  * Copyright (c) 2003 Michael Niedermayer
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include "parser.h"
  24 #include "mpegaudio.h"
  25 #include "mpegaudiodecheader.h"
  26
  27
  28 typedef struct MpegAudioParseContext {
  29     uint8_t inbuf[MPA_MAX_CODED_FRAME_SIZE];    /* input buffer */
  30     uint8_t *inbuf_ptr;
  31     int frame_size;
  32     int free_format_frame_size;
  33     int free_format_next_header;
  34     uint32_t header;
  35     int header_count;
  36 } MpegAudioParseContext;
  37
  38 #define MPA_HEADER_SIZE 4
  39
  40 /* header + layer + bitrate + freq + lsf/mpeg25 */
  41 #undef SAME_HEADER_MASK /* mpegaudio.h defines different version */
  42 #define SAME_HEADER_MASK \
  43    (0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19))
  44
  45 /* useful helper to get mpeg audio stream infos. Return -1 if error in
  46    header, otherwise the coded frame size in bytes */
  47 int ff_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bit_rate)
  48 {
  49     MPADecodeHeader s1, *s = &s1;
  50
  51     if (ff_mpa_check_header(head) != 0)
  52         return -1;
  53
  54     if (ff_mpegaudio_decode_header(s, head) != 0) {
  55         return -1;
  56     }
  57
  58     switch(s->layer) {
  59     case 1:
  60         avctx->codec_id = CODEC_ID_MP1;
  61         *frame_size = 384;
  62         break;
  63     case 2:
  64         avctx->codec_id = CODEC_ID_MP2;
  65         *frame_size = 1152;
  66         break;
  67     default:
  68     case 3:
  69         avctx->codec_id = CODEC_ID_MP3;
  70         if (s->lsf)
  71             *frame_size = 576;
  72         else
  73             *frame_size = 1152;
  74         break;
  75     }
  76
  77     *sample_rate = s->sample_rate;
  78     *channels = s->nb_channels;
  79     *bit_rate = s->bit_rate;
  80     avctx->sub_id = s->layer;
  81     return s->frame_size;
  82 }
  83
  84 static av_cold int mpegaudio_parse_init(AVCodecParserContext *s1)
  85 {
  86     MpegAudioParseContext *s = s1->priv_data;
  87     s->inbuf_ptr = s->inbuf;
  88     return 0;
  89 }
  90
  91 static int mpegaudio_parse(AVCodecParserContext *s1,
  92                            AVCodecContext *avctx,
  93                            const uint8_t **poutbuf, int *poutbuf_size,
  94                            const uint8_t *buf, int buf_size)
  95 {
  96     MpegAudioParseContext *s = s1->priv_data;
  97     int len, ret, sr, channels, bit_rate, frame_size;
  98     uint32_t header;
  99     const uint8_t *buf_ptr;
 100
 101     *poutbuf = NULL;
 102     *poutbuf_size = 0;
 103     buf_ptr = buf;
 104     while (buf_size > 0) {
 105         len = s->inbuf_ptr - s->inbuf;
 106         if (s->frame_size == 0) {
 107             /* special case for next header for first frame in free
 108                format case (XXX: find a simpler method) */
 109             if (s->free_format_next_header != 0) {
 110                 AV_WB32(s->inbuf, s->free_format_next_header);
 111                 s->inbuf_ptr = s->inbuf + 4;
 112                 s->free_format_next_header = 0;
 113                 goto got_header;
 114             }
 115             /* no header seen : find one. We need at least MPA_HEADER_SIZE
 116                bytes to parse it */
 117             len = FFMIN(MPA_HEADER_SIZE - len, buf_size);
 118             if (len > 0) {
 119                 memcpy(s->inbuf_ptr, buf_ptr, len);
 120                 buf_ptr += len;
 121                 buf_size -= len;
 122                 s->inbuf_ptr += len;
 123             }
 124             if ((s->inbuf_ptr - s->inbuf) >= MPA_HEADER_SIZE) {
 125             got_header:
 126                 header = AV_RB32(s->inbuf);
 127
 128                 ret = ff_mpa_decode_header(avctx, header, &sr, &channels, &frame_size, &bit_rate);
 129                 if (ret < 0) {
 130                     s->header_count= -2;
 131                     /* no sync found : move by one byte (inefficient, but simple!) */
 132                     memmove(s->inbuf, s->inbuf + 1, s->inbuf_ptr - s->inbuf - 1);
 133                     s->inbuf_ptr--;
 134                     dprintf(avctx, "skip %x\n", header);
 135                     /* reset free format frame size to give a chance
 136                        to get a new bitrate */
 137                     s->free_format_frame_size = 0;
 138                 } else {
 139                     if((header&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header)
 140                         s->header_count= -3;
 141                     s->header= header;
 142                     s->header_count++;
 143                     s->frame_size = ret;
 144
 145 #if 0
 146                     /* free format: prepare to compute frame size */
 147                     if (ff_mpegaudio_decode_header((MPADecodeHeader *)s, header) == 1) {
 148                         s->frame_size = -1;
 149                     }
 150 #endif
 151                     if(s->header_count > 1){
 152                         avctx->sample_rate= sr;
 153                         avctx->channels   = channels;
 154                         avctx->frame_size = frame_size;
 155                         avctx->bit_rate   = bit_rate;
 156                     }
 157                 }
 158             }
 159         } else
 160 #if 0
 161         if (s->frame_size == -1) {
 162             /* free format : find next sync to compute frame size */
 163             len = MPA_MAX_CODED_FRAME_SIZE - len;
 164             if (len > buf_size)
 165                 len = buf_size;
 166             if (len == 0) {
 167                 /* frame too long: resync */
 168                 s->frame_size = 0;
 169                 memmove(s->inbuf, s->inbuf + 1, s->inbuf_ptr - s->inbuf - 1);
 170                 s->inbuf_ptr--;
 171             } else {
 172                 uint8_t *p, *pend;
 173                 uint32_t header1;
 174                 int padding;
 175
 176                 memcpy(s->inbuf_ptr, buf_ptr, len);
 177                 /* check for header */
 178                 p = s->inbuf_ptr - 3;
 179                 pend = s->inbuf_ptr + len - 4;
 180                 while (p <= pend) {
 181                     header = AV_RB32(p);
 182                     header1 = AV_RB32(s->inbuf);
 183                     /* check with high probability that we have a
 184                        valid header */
 185                     if ((header & SAME_HEADER_MASK) ==
 186                         (header1 & SAME_HEADER_MASK)) {
 187                         /* header found: update pointers */
 188                         len = (p + 4) - s->inbuf_ptr;
 189                         buf_ptr += len;
 190                         buf_size -= len;
 191                         s->inbuf_ptr = p;
 192                         /* compute frame size */
 193                         s->free_format_next_header = header;
 194                         s->free_format_frame_size = s->inbuf_ptr - s->inbuf;
 195                         padding = (header1 >> 9) & 1;
 196                         if (s->layer == 1)
 197                             s->free_format_frame_size -= padding * 4;
 198                         else
 199                             s->free_format_frame_size -= padding;
 200                         dprintf(avctx, "free frame size=%d padding=%d\n",
 201                                 s->free_format_frame_size, padding);
 202                         ff_mpegaudio_decode_header((MPADecodeHeader *)s, header1);
 203                         goto next_data;
 204                     }
 205                     p++;
 206                 }
 207                 /* not found: simply increase pointers */
 208                 buf_ptr += len;
 209                 s->inbuf_ptr += len;
 210                 buf_size -= len;
 211             }
 212         } else
 213 #endif
 214         if (len < s->frame_size) {
 215             if (s->frame_size > MPA_MAX_CODED_FRAME_SIZE)
 216                 s->frame_size = MPA_MAX_CODED_FRAME_SIZE;
 217             len = FFMIN(s->frame_size - len, buf_size);
 218             memcpy(s->inbuf_ptr, buf_ptr, len);
 219             buf_ptr += len;
 220             s->inbuf_ptr += len;
 221             buf_size -= len;
 222         }
 223
 224         if(s->frame_size > 0 && buf_ptr - buf == s->inbuf_ptr - s->inbuf
 225            && buf_size + buf_ptr - buf >= s->frame_size){
 226             if(s->header_count > 0){
 227                 *poutbuf = buf;
 228                 *poutbuf_size = s->frame_size;
 229             }
 230             buf_ptr = buf + s->frame_size;
 231             s->inbuf_ptr = s->inbuf;
 232             s->frame_size = 0;
 233             break;
 234         }
 235
 236         //    next_data:
 237         if (s->frame_size > 0 &&
 238             (s->inbuf_ptr - s->inbuf) >= s->frame_size) {
 239             if(s->header_count > 0){
 240                 *poutbuf = s->inbuf;
 241                 *poutbuf_size = s->inbuf_ptr - s->inbuf;
 242             }
 243             s->inbuf_ptr = s->inbuf;
 244             s->frame_size = 0;
 245             break;
 246         }
 247     }
 248     return buf_ptr - buf;
 249 }
 250
 251
 252 AVCodecParser mpegaudio_parser = {
 253     { CODEC_ID_MP1, CODEC_ID_MP2, CODEC_ID_MP3 },
 254     sizeof(MpegAudioParseContext),
 255     mpegaudio_parse_init,
 256     mpegaudio_parse,
 257     NULL,
 258 };