root/libavcodec/mlp_parse.c

DEFINITIONS

1. mlp_get_major_sync_size
2. ff_mlp_read_major_sync

/*
 * 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
 */

#include <stdint.h>

#include "libavutil/channel_layout.h"
#include "get_bits.h"
#include "mlp_parse.h"
#include "mlp.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 uint64_t mlp_layout[32] = {
    AV_CH_LAYOUT_MONO,
    AV_CH_LAYOUT_STEREO,
    AV_CH_LAYOUT_2_1,
    AV_CH_LAYOUT_QUAD,
    AV_CH_LAYOUT_STEREO|AV_CH_LOW_FREQUENCY,
    AV_CH_LAYOUT_2_1|AV_CH_LOW_FREQUENCY,
    AV_CH_LAYOUT_QUAD|AV_CH_LOW_FREQUENCY,
    AV_CH_LAYOUT_SURROUND,
    AV_CH_LAYOUT_4POINT0,
    AV_CH_LAYOUT_5POINT0_BACK,
    AV_CH_LAYOUT_SURROUND|AV_CH_LOW_FREQUENCY,
    AV_CH_LAYOUT_4POINT0|AV_CH_LOW_FREQUENCY,
    AV_CH_LAYOUT_5POINT1_BACK,
    AV_CH_LAYOUT_4POINT0,
    AV_CH_LAYOUT_5POINT0_BACK,
    AV_CH_LAYOUT_SURROUND|AV_CH_LOW_FREQUENCY,
    AV_CH_LAYOUT_4POINT0|AV_CH_LOW_FREQUENCY,
    AV_CH_LAYOUT_5POINT1_BACK,
    AV_CH_LAYOUT_QUAD|AV_CH_LOW_FREQUENCY,
    AV_CH_LAYOUT_5POINT0_BACK,
    AV_CH_LAYOUT_5POINT1_BACK,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

static int mlp_get_major_sync_size(const uint8_t * buf, int bufsize)
{
    int has_extension, extensions = 0;
    int size = 28;
    if (bufsize < 28)
        return -1;

    if (AV_RB32(buf) == 0xf8726fba) {
        has_extension = buf[25] & 1;
        if (has_extension) {
            extensions = buf[26] >> 4;
            size += 2 + extensions * 2;
        }
    }
    return size;
}

/** 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, channel_arrangement, header_size;
    uint16_t checksum;

    av_assert1(get_bits_count(gb) == 0);

    header_size = mlp_get_major_sync_size(gb->buffer, gb->size_in_bits >> 3);
    if (header_size < 0 || gb->size_in_bits < header_size << 3) {
        av_log(log, AV_LOG_ERROR, "packet too short, unable to read major sync\n");
        return -1;
    }

    checksum = ff_mlp_checksum16(gb->buffer, header_size - 2);
    if (checksum != AV_RL16(gb->buffer+header_size-2)) {
        av_log(log, AV_LOG_ERROR, "major sync info header checksum error\n");
        return AVERROR_INVALIDDATA;
    }

    if (get_bits(gb, 24) != 0xf8726f) /* Sync words */
        return AVERROR_INVALIDDATA;

    mh->stream_type = get_bits(gb, 8);
    mh->header_size = header_size;

    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->channel_arrangement=
        channel_arrangement    = get_bits(gb, 5);
        mh->channels_mlp       = mlp_channels[channel_arrangement];
        mh->channel_layout_mlp = mlp_layout[channel_arrangement];
    } 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, 4);

        mh->channel_modifier_thd_stream0 = get_bits(gb, 2);
        mh->channel_modifier_thd_stream1 = get_bits(gb, 2);

        mh->channel_arrangement=
        channel_arrangement            = get_bits(gb, 5);
        mh->channels_thd_stream1       = truehd_channels(channel_arrangement);
        mh->channel_layout_thd_stream1 = truehd_layout(channel_arrangement);

        mh->channel_modifier_thd_stream2 = get_bits(gb, 2);

        channel_arrangement            = get_bits(gb, 13);
        mh->channels_thd_stream2       = truehd_channels(channel_arrangement);
        mh->channel_layout_thd_stream2 = truehd_layout(channel_arrangement);
    } else
        return AVERROR_INVALIDDATA;

    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 + (header_size - 17) * 8);

    return 0;
}