~ubuntu-branches/debian/experimental/libav/experimental

/*

 * MPEG Audio header decoder

 * Copyright (c) 2001, 2002 Fabrice Bellard

 *

 * This file is part of Libav.

 *

 * Libav 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.

 *

 * Libav 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 Libav; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

/**

 * @file

 * MPEG Audio header decoder.

 */

#include "libavutil/common.h"

#include "avcodec.h"

#include "mpegaudio.h"

#include "mpegaudiodata.h"

#include "mpegaudiodecheader.h"

int avpriv_mpegaudio_decode_header(MPADecodeHeader *s, uint32_t header)

{

    int sample_rate, frame_size, mpeg25, padding;

    int sample_rate_index, bitrate_index;

    if (header & (1<<20)) {

        s->lsf = (header & (1<<19)) ? 0 : 1;

        mpeg25 = 0;

    } else {

        s->lsf = 1;

        mpeg25 = 1;

    }

    s->layer = 4 - ((header >> 17) & 3);

    /* extract frequency */

    sample_rate_index = (header >> 10) & 3;

    if (sample_rate_index >= FF_ARRAY_ELEMS(avpriv_mpa_freq_tab))

        sample_rate_index = 0;

    sample_rate = avpriv_mpa_freq_tab[sample_rate_index] >> (s->lsf + mpeg25);

    sample_rate_index += 3 * (s->lsf + mpeg25);

    s->sample_rate_index = sample_rate_index;

    s->error_protection = ((header >> 16) & 1) ^ 1;

    s->sample_rate = sample_rate;

    bitrate_index = (header >> 12) & 0xf;

    padding = (header >> 9) & 1;

    //extension = (header >> 8) & 1;

    s->mode = (header >> 6) & 3;

    s->mode_ext = (header >> 4) & 3;

    //copyright = (header >> 3) & 1;

    //original = (header >> 2) & 1;

    //emphasis = header & 3;

    if (s->mode == MPA_MONO)

        s->nb_channels = 1;

    else

        s->nb_channels = 2;

    if (bitrate_index != 0) {

        frame_size = avpriv_mpa_bitrate_tab[s->lsf][s->layer - 1][bitrate_index];

        s->bit_rate = frame_size * 1000;

        switch(s->layer) {

        case 1:

            frame_size = (frame_size * 12000) / sample_rate;

            frame_size = (frame_size + padding) * 4;

            break;

        case 2:

            frame_size = (frame_size * 144000) / sample_rate;

            frame_size += padding;

            break;

        default:

        case 3:

            frame_size = (frame_size * 144000) / (sample_rate << s->lsf);

            frame_size += padding;

            break;

        }

        s->frame_size = frame_size;

    } else {

        /* if no frame size computed, signal it */

        return 1;

    }

#if defined(DEBUG)

    av_dlog(NULL, "layer%d, %d Hz, %d kbits/s, ",

           s->layer, s->sample_rate, s->bit_rate);

    if (s->nb_channels == 2) {

        if (s->layer == 3) {

            if (s->mode_ext & MODE_EXT_MS_STEREO)

                av_dlog(NULL, "ms-");

            if (s->mode_ext & MODE_EXT_I_STEREO)

                av_dlog(NULL, "i-");

        }

        av_dlog(NULL, "stereo");

    } else {

        av_dlog(NULL, "mono");

    }

    av_dlog(NULL, "\n");

#endif

    return 0;

}

int avpriv_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bit_rate)

{

    MPADecodeHeader s1, *s = &s1;

    if (ff_mpa_check_header(head) != 0)

        return -1;

    if (avpriv_mpegaudio_decode_header(s, head) != 0) {

        return -1;

    }

    switch(s->layer) {

    case 1:

        avctx->codec_id = AV_CODEC_ID_MP1;

        *frame_size = 384;

        break;

    case 2:

        avctx->codec_id = AV_CODEC_ID_MP2;

        *frame_size = 1152;

        break;

    default:

    case 3:

        avctx->codec_id = AV_CODEC_ID_MP3;

        if (s->lsf)

            *frame_size = 576;

        else

            *frame_size = 1152;

        break;

    }

    *sample_rate = s->sample_rate;

    *channels = s->nb_channels;

    *bit_rate = s->bit_rate;

    return s->frame_size;

}