/* * MLP parser * Copyright (c) 2007 Ian Caulfield * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ /** * @file mlp_parser.c * MLP parser */ #include "libavutil/crc.h" #include "bitstream.h" #include "parser.h" #include "mlp_parser.h" static const uint8_t mlp_quants[16] = { 16, 20, 24, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, }; static const uint8_t mlp_channels[32] = { 1, 2, 3, 4, 3, 4, 5, 3, 4, 5, 4, 5, 6, 4, 5, 4, 5, 6, 5, 5, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, }; static const uint8_t thd_chancount[13] = { // LR C LFE LRs LRvh LRc LRrs Cs Ts LRsd LRw Cvh LFE2 2, 1, 1, 2, 2, 2, 2, 1, 1, 2, 2, 1, 1 }; static int mlp_samplerate(int in) { if (in == 0xF) return 0; return (in & 8 ? 44100 : 48000) << (in & 7) ; } static int truehd_channels(int chanmap) { int channels = 0, i; for (i = 0; i < 13; i++) channels += thd_chancount[i] * ((chanmap >> i) & 1); return channels; } static int crc_init = 0; static AVCRC crc_2D[1024]; /** MLP uses checksums that seem to be based on the standard CRC algorithm, * but not (in implementation terms, the table lookup and XOR are reversed). * We can implement this behavior using a standard av_crc on all but the * last element, then XOR that with the last element. */ static uint16_t mlp_checksum16(const uint8_t *buf, unsigned int buf_size) { uint16_t crc; if (!crc_init) { av_crc_init(crc_2D, 0, 16, 0x002D, sizeof(crc_2D)); crc_init = 1; } crc = av_crc(crc_2D, 0, buf, buf_size - 2); crc ^= AV_RL16(buf + buf_size - 2); return crc; } /** Read a major sync info header - contains high level information about * the stream - sample rate, channel arrangement etc. Most of this * information is not actually necessary for decoding, only for playback. * gb must be a freshly initialized GetBitContext with no bits read. */ int ff_mlp_read_major_sync(void *log, MLPHeaderInfo *mh, GetBitContext *gb) { int ratebits; uint16_t checksum; assert(get_bits_count(gb) == 0); if (gb->size_in_bits < 28 << 3) { av_log(log, AV_LOG_ERROR, "Packet too short, unable to read major sync\n"); return -1; } checksum = mlp_checksum16(gb->buffer, 26); if (checksum != AV_RL16(gb->buffer+26)) { av_log(log, AV_LOG_ERROR, "Major sync info header checksum error\n"); return -1; } if (get_bits_long(gb, 24) != 0xf8726f) /* Sync words */ return -1; mh->stream_type = get_bits(gb, 8); if (mh->stream_type == 0xbb) { mh->group1_bits = mlp_quants[get_bits(gb, 4)]; mh->group2_bits = mlp_quants[get_bits(gb, 4)]; ratebits = get_bits(gb, 4); mh->group1_samplerate = mlp_samplerate(ratebits); mh->group2_samplerate = mlp_samplerate(get_bits(gb, 4)); skip_bits(gb, 11); mh->channels_mlp = get_bits(gb, 5); } else if (mh->stream_type == 0xba) { mh->group1_bits = 24; // TODO: Is this information actually conveyed anywhere? mh->group2_bits = 0; ratebits = get_bits(gb, 4); mh->group1_samplerate = mlp_samplerate(ratebits); mh->group2_samplerate = 0; skip_bits(gb, 8); mh->channels_thd_stream1 = get_bits(gb, 5); skip_bits(gb, 2); mh->channels_thd_stream2 = get_bits(gb, 13); } else return -1; mh->access_unit_size = 40 << (ratebits & 7); mh->access_unit_size_pow2 = 64 << (ratebits & 7); skip_bits_long(gb, 48); mh->is_vbr = get_bits1(gb); mh->peak_bitrate = (get_bits(gb, 15) * mh->group1_samplerate + 8) >> 4; mh->num_substreams = get_bits(gb, 4); skip_bits_long(gb, 4 + 11 * 8); return 0; } typedef struct MLPParseContext { ParseContext pc; int bytes_left; int in_sync; int num_substreams; } MLPParseContext; static int mlp_parse(AVCodecParserContext *s, AVCodecContext *avctx, const uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size) { MLPParseContext *mp = s->priv_data; int sync_present; uint8_t parity_bits; int next; int i, p = 0; *poutbuf_size = 0; if (buf_size == 0) return 0; if (!mp->in_sync) { // Not in sync - find a major sync header for (i = 0; i < buf_size; i++) { mp->pc.state = (mp->pc.state << 8) | buf[i]; if ((mp->pc.state & 0xfffffffe) == 0xf8726fba) { mp->in_sync = 1; mp->bytes_left = 0; break; } } if (!mp->in_sync) { ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size); return buf_size; } ff_combine_frame(&mp->pc, i - 7, &buf, &buf_size); return i - 7; } if (mp->bytes_left == 0) { // Find length of this packet /* Copy overread bytes from last frame into buffer. */ for(; mp->pc.overread>0; mp->pc.overread--) { mp->pc.buffer[mp->pc.index++]= mp->pc.buffer[mp->pc.overread_index++]; } if (mp->pc.index + buf_size < 2) { ff_combine_frame(&mp->pc, END_NOT_FOUND, &buf, &buf_size); return buf_size; } mp->bytes_left = ((mp->pc.index > 0 ? mp->pc.buffer[0] : buf[0]) << 8) | (mp->pc.index > 1 ? mp->pc.buffer[1] : buf[1-mp->pc.index]); mp->bytes_left = (mp->bytes_left & 0xfff) * 2; mp->bytes_left -= mp->pc.index; } next = (mp->bytes_left > buf_size) ? END_NOT_FOUND : mp->bytes_left; if (ff_combine_frame(&mp->pc, next, &buf, &buf_size) < 0) { mp->bytes_left -= buf_size; return buf_size; } mp->bytes_left = 0; sync_present = (AV_RB32(buf + 4) & 0xfffffffe) == 0xf8726fba; if (!sync_present) { /* The first nibble of a frame is a parity check of the 4-byte * access unit header and all the 2- or 4-byte substream headers. */ // Only check when this isn't a sync frame - syncs have a checksum. parity_bits = 0; for (i = -1; i < mp->num_substreams; i++) { parity_bits ^= buf[p++]; parity_bits ^= buf[p++]; if (i < 0 || buf[p-2] & 0x80) { parity_bits ^= buf[p++]; parity_bits ^= buf[p++]; } } if ((((parity_bits >> 4) ^ parity_bits) & 0xF) != 0xF) { av_log(avctx, AV_LOG_INFO, "mlpparse: Parity check failed.\n"); goto lost_sync; } } else { GetBitContext gb; MLPHeaderInfo mh; init_get_bits(&gb, buf + 4, (buf_size - 4) << 3); if (ff_mlp_read_major_sync(avctx, &mh, &gb) < 0) goto lost_sync; #ifdef CONFIG_AUDIO_NONSHORT avctx->bits_per_sample = mh.group1_bits; if (avctx->bits_per_sample > 16) avctx->sample_fmt = SAMPLE_FMT_S32; #endif avctx->sample_rate = mh.group1_samplerate; avctx->frame_size = mh.access_unit_size; if (mh.stream_type == 0xbb) { /* MLP stream */ avctx->channels = mlp_channels[mh.channels_mlp]; } else { /* mh.stream_type == 0xba */ /* TrueHD stream */ if (mh.channels_thd_stream2) avctx->channels = truehd_channels(mh.channels_thd_stream2); else avctx->channels = truehd_channels(mh.channels_thd_stream1); } if (!mh.is_vbr) /* Stream is CBR */ avctx->bit_rate = mh.peak_bitrate; mp->num_substreams = mh.num_substreams; } *poutbuf = buf; *poutbuf_size = buf_size; return next; lost_sync: mp->in_sync = 0; return 1; } AVCodecParser mlp_parser = { { CODEC_ID_MLP }, sizeof(MLPParseContext), NULL, mlp_parse, NULL, };