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 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 35static 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 40static 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 45static 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 50static int mlp_samplerate(int in) 51{ 52 if (in == 0xF) 53 return 0; 54 55 return (in & 8 ? 44100 : 48000) << (in & 7) ; 56} 57 58static 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 74int 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 142typedef struct MLPParseContext 143{ 144 ParseContext pc; 145 146 int bytes_left; 147 148 int in_sync; 149 150 int num_substreams; 151} MLPParseContext; 152 153static av_cold int mlp_init(AVCodecParserContext *s) 154{ 155 ff_mlp_init_crc(); 156 return 0; 157} 158 159static 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 // ignore if we do not have the data for the start of header 181 mp->pc.index + i >= 7) { 182 mp->in_sync = 1; 183 mp->bytes_left = 0; 184 break; 185 } 186 } 187 188 if (!mp->in_sync) { 189 ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size); 190 return buf_size; 191 } 192 193 ff_combine_frame(&mp->pc, i - 7, &buf, &buf_size); 194 195 return i - 7; 196 } 197 198 if (mp->bytes_left == 0) { 199 // Find length of this packet 200 201 /* Copy overread bytes from last frame into buffer. */ 202 for(; mp->pc.overread>0; mp->pc.overread--) { 203 mp->pc.buffer[mp->pc.index++]= mp->pc.buffer[mp->pc.overread_index++]; 204 } 205 206 if (mp->pc.index + buf_size < 2) { 207 ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size); 208 return buf_size; 209 } 210 211 mp->bytes_left = ((mp->pc.index > 0 ? mp->pc.buffer[0] : buf[0]) << 8) 212 | (mp->pc.index > 1 ? mp->pc.buffer[1] : buf[1-mp->pc.index]); 213 mp->bytes_left = (mp->bytes_left & 0xfff) * 2; 214 mp->bytes_left -= mp->pc.index; 215 } 216 217 next = (mp->bytes_left > buf_size) ? END_NOT_FOUND : mp->bytes_left; 218 219 if (ff_combine_frame(&mp->pc, next, &buf, &buf_size) < 0) { 220 mp->bytes_left -= buf_size; 221 return buf_size; 222 } 223 224 mp->bytes_left = 0; 225 226 sync_present = (AV_RB32(buf + 4) & 0xfffffffe) == 0xf8726fba; 227 228 if (!sync_present) { 229 /* The first nibble of a frame is a parity check of the 4-byte 230 * access unit header and all the 2- or 4-byte substream headers. */ 231 // Only check when this isn't a sync frame - syncs have a checksum. 232 233 parity_bits = 0; 234 for (i = -1; i < mp->num_substreams; i++) { 235 parity_bits ^= buf[p++]; 236 parity_bits ^= buf[p++]; 237 238 if (i < 0 || buf[p-2] & 0x80) { 239 parity_bits ^= buf[p++]; 240 parity_bits ^= buf[p++]; 241 } 242 } 243 244 if ((((parity_bits >> 4) ^ parity_bits) & 0xF) != 0xF) { 245 av_log(avctx, AV_LOG_INFO, "mlpparse: Parity check failed.\n"); 246 goto lost_sync; 247 } 248 } else { 249 GetBitContext gb; 250 MLPHeaderInfo mh; 251 252 init_get_bits(&gb, buf + 4, (buf_size - 4) << 3); 253 if (ff_mlp_read_major_sync(avctx, &mh, &gb) < 0) 254 goto lost_sync; 255 256 avctx->bits_per_raw_sample = mh.group1_bits; 257 if (avctx->bits_per_raw_sample > 16) 258 avctx->sample_fmt = SAMPLE_FMT_S32; 259 else 260 avctx->sample_fmt = SAMPLE_FMT_S16; 261 avctx->sample_rate = mh.group1_samplerate; 262 avctx->frame_size = mh.access_unit_size; 263 264 if (mh.stream_type == 0xbb) { 265 /* MLP stream */ 266 avctx->channels = mlp_channels[mh.channels_mlp]; 267 } else { /* mh.stream_type == 0xba */ 268 /* TrueHD stream */ 269 if (mh.channels_thd_stream2) 270 avctx->channels = truehd_channels(mh.channels_thd_stream2); 271 else 272 avctx->channels = truehd_channels(mh.channels_thd_stream1); 273 } 274 275 if (!mh.is_vbr) /* Stream is CBR */ 276 avctx->bit_rate = mh.peak_bitrate; 277 278 mp->num_substreams = mh.num_substreams; 279 } 280 281 *poutbuf = buf; 282 *poutbuf_size = buf_size; 283 284 return next; 285 286lost_sync: 287 mp->in_sync = 0; 288 return 1; 289} 290 291AVCodecParser mlp_parser = { 292 { CODEC_ID_MLP, CODEC_ID_TRUEHD }, 293 sizeof(MLPParseContext), 294 mlp_init, 295 mlp_parse, 296 ff_parse_close, 297}; 298