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ffmpeg / libavcodec / mlp_parser.c @ c624c219

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/*
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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 "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,
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 *  but 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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 */
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int ff_mlp_read_major_sync(void *log, MLPHeaderInfo *mh, const uint8_t *buf,
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                           unsigned int buf_size)
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{
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    GetBitContext gb;
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    int ratebits;
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    uint16_t checksum;
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    if (buf_size < 28) {
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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(buf, 26);
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    if (checksum != AV_RL16(buf+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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    init_get_bits(&gb, buf, buf_size * 8);
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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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        // First nibble of a frame is a parity check of the first few nibbles.
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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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        MLPHeaderInfo mh;
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        if (ff_mlp_read_major_sync(avctx, &mh, buf + 4, buf_size - 4) < 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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};