git.sesse.net Git - ffmpeg/blob - 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
  26
  27 typedef struct MpegAudioParseContext {
  28     uint8_t inbuf[MPA_MAX_CODED_FRAME_SIZE];    /* input buffer */
  29     uint8_t *inbuf_ptr;
  30     int frame_size;
  31     int free_format_frame_size;
  32     int free_format_next_header;
  33     uint32_t header;
  34     int header_count;
  35 } MpegAudioParseContext;
  36
  37 #define MPA_HEADER_SIZE 4
  38
  39 /* header + layer + bitrate + freq + lsf/mpeg25 */
  40 #undef SAME_HEADER_MASK /* mpegaudio.h defines different version */
  41 #define SAME_HEADER_MASK \
  42    (0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19))
  43
  44 static int mpegaudio_parse_init(AVCodecParserContext *s1)
  45 {
  46     MpegAudioParseContext *s = s1->priv_data;
  47     s->inbuf_ptr = s->inbuf;
  48     return 0;
  49 }
  50
  51 static int mpegaudio_parse(AVCodecParserContext *s1,
  52                            AVCodecContext *avctx,
  53                            uint8_t **poutbuf, int *poutbuf_size,
  54                            const uint8_t *buf, int buf_size)
  55 {
  56     MpegAudioParseContext *s = s1->priv_data;
  57     int len, ret, sr;
  58     uint32_t header;
  59     const uint8_t *buf_ptr;
  60
  61     *poutbuf = NULL;
  62     *poutbuf_size = 0;
  63     buf_ptr = buf;
  64     while (buf_size > 0) {
  65         len = s->inbuf_ptr - s->inbuf;
  66         if (s->frame_size == 0) {
  67             /* special case for next header for first frame in free
  68                format case (XXX: find a simpler method) */
  69             if (s->free_format_next_header != 0) {
  70                 s->inbuf[0] = s->free_format_next_header >> 24;
  71                 s->inbuf[1] = s->free_format_next_header >> 16;
  72                 s->inbuf[2] = s->free_format_next_header >> 8;
  73                 s->inbuf[3] = s->free_format_next_header;
  74                 s->inbuf_ptr = s->inbuf + 4;
  75                 s->free_format_next_header = 0;
  76                 goto got_header;
  77             }
  78             /* no header seen : find one. We need at least MPA_HEADER_SIZE
  79                bytes to parse it */
  80             len = FFMIN(MPA_HEADER_SIZE - len, buf_size);
  81             if (len > 0) {
  82                 memcpy(s->inbuf_ptr, buf_ptr, len);
  83                 buf_ptr += len;
  84                 buf_size -= len;
  85                 s->inbuf_ptr += len;
  86             }
  87             if ((s->inbuf_ptr - s->inbuf) >= MPA_HEADER_SIZE) {
  88             got_header:
  89                 header = (s->inbuf[0] << 24) | (s->inbuf[1] << 16) |
  90                     (s->inbuf[2] << 8) | s->inbuf[3];
  91
  92                 ret = mpa_decode_header(avctx, header, &sr);
  93                 if (ret < 0) {
  94                     s->header_count= -2;
  95                     /* no sync found : move by one byte (inefficient, but simple!) */
  96                     memmove(s->inbuf, s->inbuf + 1, s->inbuf_ptr - s->inbuf - 1);
  97                     s->inbuf_ptr--;
  98                     dprintf(avctx, "skip %x\n", header);
  99                     /* reset free format frame size to give a chance
 100                        to get a new bitrate */
 101                     s->free_format_frame_size = 0;
 102                 } else {
 103                     if((header&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header)
 104                         s->header_count= -3;
 105                     s->header= header;
 106                     s->header_count++;
 107                     s->frame_size = ret;
 108
 109 #if 0
 110                     /* free format: prepare to compute frame size */
 111                     if (decode_header(s, header) == 1) {
 112                         s->frame_size = -1;
 113                     }
 114 #endif
 115                 }
 116                 if(s->header_count > 1)
 117                     avctx->sample_rate= sr;
 118             }
 119         } else
 120 #if 0
 121         if (s->frame_size == -1) {
 122             /* free format : find next sync to compute frame size */
 123             len = MPA_MAX_CODED_FRAME_SIZE - len;
 124             if (len > buf_size)
 125                 len = buf_size;
 126             if (len == 0) {
 127                 /* frame too long: resync */
 128                 s->frame_size = 0;
 129                 memmove(s->inbuf, s->inbuf + 1, s->inbuf_ptr - s->inbuf - 1);
 130                 s->inbuf_ptr--;
 131             } else {
 132                 uint8_t *p, *pend;
 133                 uint32_t header1;
 134                 int padding;
 135
 136                 memcpy(s->inbuf_ptr, buf_ptr, len);
 137                 /* check for header */
 138                 p = s->inbuf_ptr - 3;
 139                 pend = s->inbuf_ptr + len - 4;
 140                 while (p <= pend) {
 141                     header = (p[0] << 24) | (p[1] << 16) |
 142                         (p[2] << 8) | p[3];
 143                     header1 = (s->inbuf[0] << 24) | (s->inbuf[1] << 16) |
 144                         (s->inbuf[2] << 8) | s->inbuf[3];
 145                     /* check with high probability that we have a
 146                        valid header */
 147                     if ((header & SAME_HEADER_MASK) ==
 148                         (header1 & SAME_HEADER_MASK)) {
 149                         /* header found: update pointers */
 150                         len = (p + 4) - s->inbuf_ptr;
 151                         buf_ptr += len;
 152                         buf_size -= len;
 153                         s->inbuf_ptr = p;
 154                         /* compute frame size */
 155                         s->free_format_next_header = header;
 156                         s->free_format_frame_size = s->inbuf_ptr - s->inbuf;
 157                         padding = (header1 >> 9) & 1;
 158                         if (s->layer == 1)
 159                             s->free_format_frame_size -= padding * 4;
 160                         else
 161                             s->free_format_frame_size -= padding;
 162                         dprintf(avctx, "free frame size=%d padding=%d\n",
 163                                 s->free_format_frame_size, padding);
 164                         decode_header(s, header1);
 165                         goto next_data;
 166                     }
 167                     p++;
 168                 }
 169                 /* not found: simply increase pointers */
 170                 buf_ptr += len;
 171                 s->inbuf_ptr += len;
 172                 buf_size -= len;
 173             }
 174         } else
 175 #endif
 176         if (len < s->frame_size) {
 177             if (s->frame_size > MPA_MAX_CODED_FRAME_SIZE)
 178                 s->frame_size = MPA_MAX_CODED_FRAME_SIZE;
 179             len = FFMIN(s->frame_size - len, buf_size);
 180             memcpy(s->inbuf_ptr, buf_ptr, len);
 181             buf_ptr += len;
 182             s->inbuf_ptr += len;
 183             buf_size -= len;
 184         }
 185
 186         if(s->frame_size > 0 && buf_ptr - buf == s->inbuf_ptr - s->inbuf
 187            && buf_size + buf_ptr - buf >= s->frame_size){
 188             if(s->header_count > 0){
 189                 *poutbuf = buf;
 190                 *poutbuf_size = s->frame_size;
 191             }
 192             buf_ptr = buf + s->frame_size;
 193             s->inbuf_ptr = s->inbuf;
 194             s->frame_size = 0;
 195             break;
 196         }
 197
 198         //    next_data:
 199         if (s->frame_size > 0 &&
 200             (s->inbuf_ptr - s->inbuf) >= s->frame_size) {
 201             if(s->header_count > 0){
 202                 *poutbuf = s->inbuf;
 203                 *poutbuf_size = s->inbuf_ptr - s->inbuf;
 204             }
 205             s->inbuf_ptr = s->inbuf;
 206             s->frame_size = 0;
 207             break;
 208         }
 209     }
 210     return buf_ptr - buf;
 211 }
 212
 213
 214 AVCodecParser mpegaudio_parser = {
 215     { CODEC_ID_MP2, CODEC_ID_MP3 },
 216     sizeof(MpegAudioParseContext),
 217     mpegaudio_parse_init,
 218     mpegaudio_parse,
 219     NULL,
 220 };