PeerStreamer

/*

 * AC-3 parser

 * Copyright (c) 2003 Fabrice Bellard

 * Copyright (c) 2003 Michael Niedermayer

 *

 * 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 "parser.h"

#include "ac3_parser.h"

#include "aac_ac3_parser.h"

#include "get_bits.h"

#include "libavcore/audioconvert.h"

#define AC3_HEADER_SIZE 7

static const uint8_t eac3_blocks[4] = {

    1, 2, 3, 6

};

int ff_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)

{

    int frame_size_code;

    memset(hdr, 0, sizeof(*hdr));

    hdr->sync_word = get_bits(gbc, 16);

    if(hdr->sync_word != 0x0B77)

        return AAC_AC3_PARSE_ERROR_SYNC;

    /* read ahead to bsid to distinguish between AC-3 and E-AC-3 */

    hdr->bitstream_id = show_bits_long(gbc, 29) & 0x1F;

    if(hdr->bitstream_id > 16)

        return AAC_AC3_PARSE_ERROR_BSID;

    hdr->num_blocks = 6;

    /* set default mix levels */

    hdr->center_mix_level   = 1;  // -4.5dB

    hdr->surround_mix_level = 1;  // -6.0dB

    if(hdr->bitstream_id <= 10) {

        /* Normal AC-3 */

        hdr->crc1 = get_bits(gbc, 16);

        hdr->sr_code = get_bits(gbc, 2);

        if(hdr->sr_code == 3)

            return AAC_AC3_PARSE_ERROR_SAMPLE_RATE;

        frame_size_code = get_bits(gbc, 6);

        if(frame_size_code > 37)

            return AAC_AC3_PARSE_ERROR_FRAME_SIZE;

        skip_bits(gbc, 5); // skip bsid, already got it

        skip_bits(gbc, 3); // skip bitstream mode

        hdr->channel_mode = get_bits(gbc, 3);

        if(hdr->channel_mode == AC3_CHMODE_STEREO) {

            skip_bits(gbc, 2); // skip dsurmod

        } else {

            if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO)

                hdr->center_mix_level = get_bits(gbc, 2);

            if(hdr->channel_mode & 4)

                hdr->surround_mix_level = get_bits(gbc, 2);

        }

        hdr->lfe_on = get_bits1(gbc);

        hdr->sr_shift = FFMAX(hdr->bitstream_id, 8) - 8;

        hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code] >> hdr->sr_shift;

        hdr->bit_rate = (ff_ac3_bitrate_tab[frame_size_code>>1] * 1000) >> hdr->sr_shift;

        hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;

        hdr->frame_size = ff_ac3_frame_size_tab[frame_size_code][hdr->sr_code] * 2;

        hdr->frame_type = EAC3_FRAME_TYPE_AC3_CONVERT; //EAC3_FRAME_TYPE_INDEPENDENT;

        hdr->substreamid = 0;

    } else {

        /* Enhanced AC-3 */

        hdr->crc1 = 0;

        hdr->frame_type = get_bits(gbc, 2);

        if(hdr->frame_type == EAC3_FRAME_TYPE_RESERVED)

            return AAC_AC3_PARSE_ERROR_FRAME_TYPE;

        hdr->substreamid = get_bits(gbc, 3);

        hdr->frame_size = (get_bits(gbc, 11) + 1) << 1;

        if(hdr->frame_size < AC3_HEADER_SIZE)

            return AAC_AC3_PARSE_ERROR_FRAME_SIZE;

        hdr->sr_code = get_bits(gbc, 2);

        if (hdr->sr_code == 3) {

            int sr_code2 = get_bits(gbc, 2);

            if(sr_code2 == 3)

                return AAC_AC3_PARSE_ERROR_SAMPLE_RATE;

            hdr->sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;

            hdr->sr_shift = 1;

        } else {

            hdr->num_blocks = eac3_blocks[get_bits(gbc, 2)];

            hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code];

            hdr->sr_shift = 0;

        }

        hdr->channel_mode = get_bits(gbc, 3);

        hdr->lfe_on = get_bits1(gbc);

        hdr->bit_rate = (uint32_t)(8.0 * hdr->frame_size * hdr->sample_rate /

                        (hdr->num_blocks * 256.0));

        hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;

    }

    hdr->channel_layout = ff_ac3_channel_layout_tab[hdr->channel_mode];

    if (hdr->lfe_on)

        hdr->channel_layout |= AV_CH_LOW_FREQUENCY;

    return 0;

}

static int ac3_sync(uint64_t state, AACAC3ParseContext *hdr_info,

        int *need_next_header, int *new_frame_start)

{

    int err;

    union {

        uint64_t u64;

        uint8_t  u8[8];

    } tmp = { av_be2ne64(state) };

    AC3HeaderInfo hdr;

    GetBitContext gbc;

    init_get_bits(&gbc, tmp.u8+8-AC3_HEADER_SIZE, 54);

    err = ff_ac3_parse_header(&gbc, &hdr);

    if(err < 0)

        return 0;

    hdr_info->sample_rate = hdr.sample_rate;

    hdr_info->bit_rate = hdr.bit_rate;

    hdr_info->channels = hdr.channels;

    hdr_info->channel_layout = hdr.channel_layout;

    hdr_info->samples = hdr.num_blocks * 256;

    if(hdr.bitstream_id>10)

        hdr_info->codec_id = CODEC_ID_EAC3;

    else if (hdr_info->codec_id == CODEC_ID_NONE)

        hdr_info->codec_id = CODEC_ID_AC3;

    *need_next_header = (hdr.frame_type != EAC3_FRAME_TYPE_AC3_CONVERT);

    *new_frame_start  = (hdr.frame_type != EAC3_FRAME_TYPE_DEPENDENT);

    return hdr.frame_size;

}

static av_cold int ac3_parse_init(AVCodecParserContext *s1)

{

    AACAC3ParseContext *s = s1->priv_data;

    s->header_size = AC3_HEADER_SIZE;

    s->sync = ac3_sync;

    return 0;

}

AVCodecParser ff_ac3_parser = {

    { CODEC_ID_AC3, CODEC_ID_EAC3 },

    sizeof(AACAC3ParseContext),

    ac3_parse_init,

    ff_aac_ac3_parse,

    ff_parse_close,

};