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 mlp_parser.c
  24  * MLP parser
  25  */
  26
  27 #include <stdint.h>
  28
  29 #include "libavutil/crc.h"
  30 #include "bitstream.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 int mlp_parse(AVCodecParserContext *s,
 154                      AVCodecContext *avctx,
 155                      const uint8_t **poutbuf, int *poutbuf_size,
 156                      const uint8_t *buf, int buf_size)
 157 {
 158     MLPParseContext *mp = s->priv_data;
 159     int sync_present;
 160     uint8_t parity_bits;
 161     int next;
 162     int i, p = 0;
 163
 164     *poutbuf_size = 0;
 165     if (buf_size == 0)
 166         return 0;
 167
 168     if (!mp->in_sync) {
 169         // Not in sync - find a major sync header
 170
 171         for (i = 0; i < buf_size; i++) {
 172             mp->pc.state = (mp->pc.state << 8) | buf[i];
 173             if ((mp->pc.state & 0xfffffffe) == 0xf8726fba) {
 174                 mp->in_sync = 1;
 175                 mp->bytes_left = 0;
 176                 break;
 177             }
 178         }
 179
 180         if (!mp->in_sync) {
 181             ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size);
 182             return buf_size;
 183         }
 184
 185         ff_combine_frame(&mp->pc, i - 7, &buf, &buf_size);
 186
 187         return i - 7;
 188     }
 189
 190     if (mp->bytes_left == 0) {
 191         // Find length of this packet
 192
 193         /* Copy overread bytes from last frame into buffer. */
 194         for(; mp->pc.overread>0; mp->pc.overread--) {
 195             mp->pc.buffer[mp->pc.index++]= mp->pc.buffer[mp->pc.overread_index++];
 196         }
 197
 198         if (mp->pc.index + buf_size < 2) {
 199             ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size);
 200             return buf_size;
 201         }
 202
 203         mp->bytes_left = ((mp->pc.index > 0 ? mp->pc.buffer[0] : buf[0]) << 8)
 204                        |  (mp->pc.index > 1 ? mp->pc.buffer[1] : buf[1-mp->pc.index]);
 205         mp->bytes_left = (mp->bytes_left & 0xfff) * 2;
 206         mp->bytes_left -= mp->pc.index;
 207     }
 208
 209     next = (mp->bytes_left > buf_size) ? END_NOT_FOUND : mp->bytes_left;
 210
 211     if (ff_combine_frame(&mp->pc, next, &buf, &buf_size) < 0) {
 212         mp->bytes_left -= buf_size;
 213         return buf_size;
 214     }
 215
 216     mp->bytes_left = 0;
 217
 218     sync_present = (AV_RB32(buf + 4) & 0xfffffffe) == 0xf8726fba;
 219
 220     if (!sync_present) {
 221         /* The first nibble of a frame is a parity check of the 4-byte
 222          * access unit header and all the 2- or 4-byte substream headers. */
 223         // Only check when this isn't a sync frame - syncs have a checksum.
 224
 225         parity_bits = 0;
 226         for (i = -1; i < mp->num_substreams; i++) {
 227             parity_bits ^= buf[p++];
 228             parity_bits ^= buf[p++];
 229
 230             if (i < 0 || buf[p-2] & 0x80) {
 231                 parity_bits ^= buf[p++];
 232                 parity_bits ^= buf[p++];
 233             }
 234         }
 235
 236         if ((((parity_bits >> 4) ^ parity_bits) & 0xF) != 0xF) {
 237             av_log(avctx, AV_LOG_INFO, "mlpparse: Parity check failed.\n");
 238             goto lost_sync;
 239         }
 240     } else {
 241         GetBitContext gb;
 242         MLPHeaderInfo mh;
 243
 244         init_get_bits(&gb, buf + 4, (buf_size - 4) << 3);
 245         if (ff_mlp_read_major_sync(avctx, &mh, &gb) < 0)
 246             goto lost_sync;
 247
 248 #ifdef CONFIG_AUDIO_NONSHORT
 249         avctx->bits_per_sample = mh.group1_bits;
 250         if (avctx->bits_per_sample > 16)
 251             avctx->sample_fmt = SAMPLE_FMT_S32;
 252 #endif
 253         avctx->sample_rate = mh.group1_samplerate;
 254         avctx->frame_size = mh.access_unit_size;
 255
 256         if (mh.stream_type == 0xbb) {
 257             /* MLP stream */
 258             avctx->channels = mlp_channels[mh.channels_mlp];
 259         } else { /* mh.stream_type == 0xba */
 260             /* TrueHD stream */
 261             if (mh.channels_thd_stream2)
 262                 avctx->channels = truehd_channels(mh.channels_thd_stream2);
 263             else
 264                 avctx->channels = truehd_channels(mh.channels_thd_stream1);
 265         }
 266
 267         if (!mh.is_vbr) /* Stream is CBR */
 268             avctx->bit_rate = mh.peak_bitrate;
 269
 270         mp->num_substreams = mh.num_substreams;
 271     }
 272
 273     *poutbuf = buf;
 274     *poutbuf_size = buf_size;
 275
 276     return next;
 277
 278 lost_sync:
 279     mp->in_sync = 0;
 280     return 1;
 281 }
 282
 283 AVCodecParser mlp_parser = {
 284     { CODEC_ID_MLP },
 285     sizeof(MLPParseContext),
 286     ff_mlp_init_crc2D,
 287     mlp_parse,
 288     NULL,
 289 };