libavcodec/mlp_parser.c

   1 /*
   2  * MLP parser
   3  * Copyright (c) 2007 Ian Caulfield
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file libavcodec/mlp_parser.c
  24  * MLP parser
  25  */
  26
  27 #include <stdint.h>
  28
  29 #include "libavutil/crc.h"
  30 #include "get_bits.h"
  31 #include "parser.h"
  32 #include "mlp_parser.h"
  33 #include "mlp.h"
  34
  35 static const uint8_t mlp_quants[16] = {
  36     16, 20, 24, 0, 0, 0, 0, 0,
  37      0,  0,  0, 0, 0, 0, 0, 0,
  38 };
  39
  40 static const uint8_t mlp_channels[32] = {
  41     1, 2, 3, 4, 3, 4, 5, 3, 4, 5, 4, 5, 6, 4, 5, 4,
  42     5, 6, 5, 5, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  43 };
  44
  45 static const uint8_t thd_chancount[13] = {
  46 //  LR    C   LFE  LRs LRvh  LRc LRrs  Cs   Ts  LRsd  LRw  Cvh  LFE2
  47      2,   1,   1,   2,   2,   2,   2,   1,   1,   2,   2,   1,   1
  48 };
  49
  50 static int mlp_samplerate(int in)
  51 {
  52     if (in == 0xF)
  53         return 0;
  54
  55     return (in & 8 ? 44100 : 48000) << (in & 7) ;
  56 }
  57
  58 static int truehd_channels(int chanmap)
  59 {
  60     int channels = 0, i;
  61
  62     for (i = 0; i < 13; i++)
  63         channels += thd_chancount[i] * ((chanmap >> i) & 1);
  64
  65     return channels;
  66 }
  67
  68 /** Read a major sync info header - contains high level information about
  69  *  the stream - sample rate, channel arrangement etc. Most of this
  70  *  information is not actually necessary for decoding, only for playback.
  71  *  gb must be a freshly initialized GetBitContext with no bits read.
  72  */
  73
  74 int ff_mlp_read_major_sync(void *log, MLPHeaderInfo *mh, GetBitContext *gb)
  75 {
  76     int ratebits;
  77     uint16_t checksum;
  78
  79     assert(get_bits_count(gb) == 0);
  80
  81     if (gb->size_in_bits < 28 << 3) {
  82         av_log(log, AV_LOG_ERROR, "packet too short, unable to read major sync\n");
  83         return -1;
  84     }
  85
  86     checksum = ff_mlp_checksum16(gb->buffer, 26);
  87     if (checksum != AV_RL16(gb->buffer+26)) {
  88         av_log(log, AV_LOG_ERROR, "major sync info header checksum error\n");
  89         return -1;
  90     }
  91
  92     if (get_bits_long(gb, 24) != 0xf8726f) /* Sync words */
  93         return -1;
  94
  95     mh->stream_type = get_bits(gb, 8);
  96
  97     if (mh->stream_type == 0xbb) {
  98         mh->group1_bits = mlp_quants[get_bits(gb, 4)];
  99         mh->group2_bits = mlp_quants[get_bits(gb, 4)];
 100
 101         ratebits = get_bits(gb, 4);
 102         mh->group1_samplerate = mlp_samplerate(ratebits);
 103         mh->group2_samplerate = mlp_samplerate(get_bits(gb, 4));
 104
 105         skip_bits(gb, 11);
 106
 107         mh->channels_mlp = get_bits(gb, 5);
 108     } else if (mh->stream_type == 0xba) {
 109         mh->group1_bits = 24; // TODO: Is this information actually conveyed anywhere?
 110         mh->group2_bits = 0;
 111
 112         ratebits = get_bits(gb, 4);
 113         mh->group1_samplerate = mlp_samplerate(ratebits);
 114         mh->group2_samplerate = 0;
 115
 116         skip_bits(gb, 8);
 117
 118         mh->channels_thd_stream1 = get_bits(gb, 5);
 119
 120         skip_bits(gb, 2);
 121
 122         mh->channels_thd_stream2 = get_bits(gb, 13);
 123     } else
 124         return -1;
 125
 126     mh->access_unit_size = 40 << (ratebits & 7);
 127     mh->access_unit_size_pow2 = 64 << (ratebits & 7);
 128
 129     skip_bits_long(gb, 48);
 130
 131     mh->is_vbr = get_bits1(gb);
 132
 133     mh->peak_bitrate = (get_bits(gb, 15) * mh->group1_samplerate + 8) >> 4;
 134
 135     mh->num_substreams = get_bits(gb, 4);
 136
 137     skip_bits_long(gb, 4 + 11 * 8);
 138
 139     return 0;
 140 }
 141
 142 typedef struct MLPParseContext
 143 {
 144     ParseContext pc;
 145
 146     int bytes_left;
 147
 148     int in_sync;
 149
 150     int num_substreams;
 151 } MLPParseContext;
 152
 153 static av_cold int mlp_init(AVCodecParserContext *s)
 154 {
 155     ff_mlp_init_crc();
 156     return 0;
 157 }
 158
 159 static int mlp_parse(AVCodecParserContext *s,
 160                      AVCodecContext *avctx,
 161                      const uint8_t **poutbuf, int *poutbuf_size,
 162                      const uint8_t *buf, int buf_size)
 163 {
 164     MLPParseContext *mp = s->priv_data;
 165     int sync_present;
 166     uint8_t parity_bits;
 167     int next;
 168     int i, p = 0;
 169
 170     *poutbuf_size = 0;
 171     if (buf_size == 0)
 172         return 0;
 173
 174     if (!mp->in_sync) {
 175         // Not in sync - find a major sync header
 176
 177         for (i = 0; i < buf_size; i++) {
 178             mp->pc.state = (mp->pc.state << 8) | buf[i];
 179             if ((mp->pc.state & 0xfffffffe) == 0xf8726fba) {
 180                 mp->in_sync = 1;
 181                 mp->bytes_left = 0;
 182                 break;
 183             }
 184         }
 185
 186         if (!mp->in_sync) {
 187             ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size);
 188             return buf_size;
 189         }
 190
 191         ff_combine_frame(&mp->pc, i - 7, &buf, &buf_size);
 192
 193         return i - 7;
 194     }
 195
 196     if (mp->bytes_left == 0) {
 197         // Find length of this packet
 198
 199         /* Copy overread bytes from last frame into buffer. */
 200         for(; mp->pc.overread>0; mp->pc.overread--) {
 201             mp->pc.buffer[mp->pc.index++]= mp->pc.buffer[mp->pc.overread_index++];
 202         }
 203
 204         if (mp->pc.index + buf_size < 2) {
 205             ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size);
 206             return buf_size;
 207         }
 208
 209         mp->bytes_left = ((mp->pc.index > 0 ? mp->pc.buffer[0] : buf[0]) << 8)
 210                        |  (mp->pc.index > 1 ? mp->pc.buffer[1] : buf[1-mp->pc.index]);
 211         mp->bytes_left = (mp->bytes_left & 0xfff) * 2;
 212         mp->bytes_left -= mp->pc.index;
 213     }
 214
 215     next = (mp->bytes_left > buf_size) ? END_NOT_FOUND : mp->bytes_left;
 216
 217     if (ff_combine_frame(&mp->pc, next, &buf, &buf_size) < 0) {
 218         mp->bytes_left -= buf_size;
 219         return buf_size;
 220     }
 221
 222     mp->bytes_left = 0;
 223
 224     sync_present = (AV_RB32(buf + 4) & 0xfffffffe) == 0xf8726fba;
 225
 226     if (!sync_present) {
 227         /* The first nibble of a frame is a parity check of the 4-byte
 228          * access unit header and all the 2- or 4-byte substream headers. */
 229         // Only check when this isn't a sync frame - syncs have a checksum.
 230
 231         parity_bits = 0;
 232         for (i = -1; i < mp->num_substreams; i++) {
 233             parity_bits ^= buf[p++];
 234             parity_bits ^= buf[p++];
 235
 236             if (i < 0 || buf[p-2] & 0x80) {
 237                 parity_bits ^= buf[p++];
 238                 parity_bits ^= buf[p++];
 239             }
 240         }
 241
 242         if ((((parity_bits >> 4) ^ parity_bits) & 0xF) != 0xF) {
 243             av_log(avctx, AV_LOG_INFO, "mlpparse: Parity check failed.\n");
 244             goto lost_sync;
 245         }
 246     } else {
 247         GetBitContext gb;
 248         MLPHeaderInfo mh;
 249
 250         init_get_bits(&gb, buf + 4, (buf_size - 4) << 3);
 251         if (ff_mlp_read_major_sync(avctx, &mh, &gb) < 0)
 252             goto lost_sync;
 253
 254         avctx->bits_per_raw_sample = mh.group1_bits;
 255         if (avctx->bits_per_raw_sample > 16)
 256             avctx->sample_fmt = SAMPLE_FMT_S32;
 257         else
 258             avctx->sample_fmt = SAMPLE_FMT_S16;
 259         avctx->sample_rate = mh.group1_samplerate;
 260         avctx->frame_size = mh.access_unit_size;
 261
 262         if (mh.stream_type == 0xbb) {
 263             /* MLP stream */
 264             avctx->channels = mlp_channels[mh.channels_mlp];
 265         } else { /* mh.stream_type == 0xba */
 266             /* TrueHD stream */
 267             if (mh.channels_thd_stream2)
 268                 avctx->channels = truehd_channels(mh.channels_thd_stream2);
 269             else
 270                 avctx->channels = truehd_channels(mh.channels_thd_stream1);
 271         }
 272
 273         if (!mh.is_vbr) /* Stream is CBR */
 274             avctx->bit_rate = mh.peak_bitrate;
 275
 276         mp->num_substreams = mh.num_substreams;
 277     }
 278
 279     *poutbuf = buf;
 280     *poutbuf_size = buf_size;
 281
 282     return next;
 283
 284 lost_sync:
 285     mp->in_sync = 0;
 286     return 1;
 287 }
 288
 289 AVCodecParser mlp_parser = {
 290     { CODEC_ID_MLP, CODEC_ID_TRUEHD },
 291     sizeof(MLPParseContext),
 292     mlp_init,
 293     mlp_parse,
 294     NULL,
 295 };