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)
  48 {
  49     MPADecodeContext s1, *s = &s1;
  50     s1.avctx = avctx;
  51
  52     if (ff_mpa_check_header(head) != 0)
  53         return -1;
  54
  55     if (ff_mpegaudio_decode_header(s, head) != 0) {
  56         return -1;
  57     }
  58
  59     switch(s->layer) {
  60     case 1:
  61         avctx->frame_size = 384;
  62         break;
  63     case 2:
  64         avctx->frame_size = 1152;
  65         break;
  66     default:
  67     case 3:
  68         if (s->lsf)
  69             avctx->frame_size = 576;
  70         else
  71             avctx->frame_size = 1152;
  72         break;
  73     }
  74
  75     *sample_rate = s->sample_rate;
  76     avctx->channels = s->nb_channels;
  77     avctx->bit_rate = s->bit_rate;
  78     avctx->sub_id = s->layer;
  79     return s->frame_size;
  80 }
  81
  82 static int mpegaudio_parse_init(AVCodecParserContext *s1)
  83 {
  84     MpegAudioParseContext *s = s1->priv_data;
  85     s->inbuf_ptr = s->inbuf;
  86     return 0;
  87 }
  88
  89 static int mpegaudio_parse(AVCodecParserContext *s1,
  90                            AVCodecContext *avctx,
  91                            const uint8_t **poutbuf, int *poutbuf_size,
  92                            const uint8_t *buf, int buf_size)
  93 {
  94     MpegAudioParseContext *s = s1->priv_data;
  95     int len, ret, sr;
  96     uint32_t header;
  97     const uint8_t *buf_ptr;
  98
  99     *poutbuf = NULL;
 100     *poutbuf_size = 0;
 101     buf_ptr = buf;
 102     while (buf_size > 0) {
 103         len = s->inbuf_ptr - s->inbuf;
 104         if (s->frame_size == 0) {
 105             /* special case for next header for first frame in free
 106                format case (XXX: find a simpler method) */
 107             if (s->free_format_next_header != 0) {
 108                 AV_WB32(s->inbuf, s->free_format_next_header);
 109                 s->inbuf_ptr = s->inbuf + 4;
 110                 s->free_format_next_header = 0;
 111                 goto got_header;
 112             }
 113             /* no header seen : find one. We need at least MPA_HEADER_SIZE
 114                bytes to parse it */
 115             len = FFMIN(MPA_HEADER_SIZE - len, buf_size);
 116             if (len > 0) {
 117                 memcpy(s->inbuf_ptr, buf_ptr, len);
 118                 buf_ptr += len;
 119                 buf_size -= len;
 120                 s->inbuf_ptr += len;
 121             }
 122             if ((s->inbuf_ptr - s->inbuf) >= MPA_HEADER_SIZE) {
 123             got_header:
 124                 header = AV_RB32(s->inbuf);
 125
 126                 ret = ff_mpa_decode_header(avctx, header, &sr);
 127                 if (ret < 0) {
 128                     s->header_count= -2;
 129                     /* no sync found : move by one byte (inefficient, but simple!) */
 130                     memmove(s->inbuf, s->inbuf + 1, s->inbuf_ptr - s->inbuf - 1);
 131                     s->inbuf_ptr--;
 132                     dprintf(avctx, "skip %x\n", header);
 133                     /* reset free format frame size to give a chance
 134                        to get a new bitrate */
 135                     s->free_format_frame_size = 0;
 136                 } else {
 137                     if((header&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header)
 138                         s->header_count= -3;
 139                     s->header= header;
 140                     s->header_count++;
 141                     s->frame_size = ret;
 142
 143 #if 0
 144                     /* free format: prepare to compute frame size */
 145                     if (ff_mpegaudio_decode_header(s, header) == 1) {
 146                         s->frame_size = -1;
 147                     }
 148 #endif
 149                     if(s->header_count > 1)
 150                         avctx->sample_rate= sr;
 151                 }
 152             }
 153         } else
 154 #if 0
 155         if (s->frame_size == -1) {
 156             /* free format : find next sync to compute frame size */
 157             len = MPA_MAX_CODED_FRAME_SIZE - len;
 158             if (len > buf_size)
 159                 len = buf_size;
 160             if (len == 0) {
 161                 /* frame too long: resync */
 162                 s->frame_size = 0;
 163                 memmove(s->inbuf, s->inbuf + 1, s->inbuf_ptr - s->inbuf - 1);
 164                 s->inbuf_ptr--;
 165             } else {
 166                 uint8_t *p, *pend;
 167                 uint32_t header1;
 168                 int padding;
 169
 170                 memcpy(s->inbuf_ptr, buf_ptr, len);
 171                 /* check for header */
 172                 p = s->inbuf_ptr - 3;
 173                 pend = s->inbuf_ptr + len - 4;
 174                 while (p <= pend) {
 175                     header = AV_RB32(p);
 176                     header1 = AV_RB32(s->inbuf);
 177                     /* check with high probability that we have a
 178                        valid header */
 179                     if ((header & SAME_HEADER_MASK) ==
 180                         (header1 & SAME_HEADER_MASK)) {
 181                         /* header found: update pointers */
 182                         len = (p + 4) - s->inbuf_ptr;
 183                         buf_ptr += len;
 184                         buf_size -= len;
 185                         s->inbuf_ptr = p;
 186                         /* compute frame size */
 187                         s->free_format_next_header = header;
 188                         s->free_format_frame_size = s->inbuf_ptr - s->inbuf;
 189                         padding = (header1 >> 9) & 1;
 190                         if (s->layer == 1)
 191                             s->free_format_frame_size -= padding * 4;
 192                         else
 193                             s->free_format_frame_size -= padding;
 194                         dprintf(avctx, "free frame size=%d padding=%d\n",
 195                                 s->free_format_frame_size, padding);
 196                         ff_mpegaudio_decode_header(s, header1);
 197                         goto next_data;
 198                     }
 199                     p++;
 200                 }
 201                 /* not found: simply increase pointers */
 202                 buf_ptr += len;
 203                 s->inbuf_ptr += len;
 204                 buf_size -= len;
 205             }
 206         } else
 207 #endif
 208         if (len < s->frame_size) {
 209             if (s->frame_size > MPA_MAX_CODED_FRAME_SIZE)
 210                 s->frame_size = MPA_MAX_CODED_FRAME_SIZE;
 211             len = FFMIN(s->frame_size - len, buf_size);
 212             memcpy(s->inbuf_ptr, buf_ptr, len);
 213             buf_ptr += len;
 214             s->inbuf_ptr += len;
 215             buf_size -= len;
 216         }
 217
 218         if(s->frame_size > 0 && buf_ptr - buf == s->inbuf_ptr - s->inbuf
 219            && buf_size + buf_ptr - buf >= s->frame_size){
 220             if(s->header_count > 0){
 221                 *poutbuf = buf;
 222                 *poutbuf_size = s->frame_size;
 223             }
 224             buf_ptr = buf + s->frame_size;
 225             s->inbuf_ptr = s->inbuf;
 226             s->frame_size = 0;
 227             break;
 228         }
 229
 230         //    next_data:
 231         if (s->frame_size > 0 &&
 232             (s->inbuf_ptr - s->inbuf) >= s->frame_size) {
 233             if(s->header_count > 0){
 234                 *poutbuf = s->inbuf;
 235                 *poutbuf_size = s->inbuf_ptr - s->inbuf;
 236             }
 237             s->inbuf_ptr = s->inbuf;
 238             s->frame_size = 0;
 239             break;
 240         }
 241     }
 242     return buf_ptr - buf;
 243 }
 244
 245
 246 AVCodecParser mpegaudio_parser = {
 247     { CODEC_ID_MP2, CODEC_ID_MP3 },
 248     sizeof(MpegAudioParseContext),
 249     mpegaudio_parse_init,
 250     mpegaudio_parse,
 251     NULL,
 252 };