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