FFmpeg/libavformat/amr.c

/*
 * amr file format
 * Copyright (c) 2001 ffmpeg project
 *
 * 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
 */

/*
Write and read amr data according to RFC3267, http://www.ietf.org/rfc/rfc3267.txt?number=3267

Only mono files are supported.

*/
#include "avformat.h"

static const char AMR_header [] = "#!AMR\n";
static const char AMRWB_header [] = "#!AMR-WB\n";

#if CONFIG_AMR_MUXER
static int amr_write_header(AVFormatContext *s)
{
    AVIOContext *pb = s->pb;
    AVCodecContext *enc = s->streams[0]->codec;

    s->priv_data = NULL;

    if (enc->codec_id == CODEC_ID_AMR_NB)
    {
        avio_write(pb, AMR_header,   sizeof(AMR_header)   - 1); /* magic number */
    }
    else if(enc->codec_id == CODEC_ID_AMR_WB)
    {
        avio_write(pb, AMRWB_header, sizeof(AMRWB_header) - 1); /* magic number */
    }
    else
    {
        return -1;
    }
    avio_flush(pb);
    return 0;
}

static int amr_write_packet(AVFormatContext *s, AVPacket *pkt)
{
    avio_write(s->pb, pkt->data, pkt->size);
    avio_flush(s->pb);
    return 0;
}
#endif /* CONFIG_AMR_MUXER */

static int amr_probe(AVProbeData *p)
{
    //Only check for "#!AMR" which could be amr-wb, amr-nb.
    //This will also trigger multichannel files: "#!AMR_MC1.0\n" and
    //"#!AMR-WB_MC1.0\n" (not supported)

    if(memcmp(p->buf,AMR_header,5)==0)
        return AVPROBE_SCORE_MAX;
    else
        return 0;
}

/* amr input */
static int amr_read_header(AVFormatContext *s,
                           AVFormatParameters *ap)
{
    AVIOContext *pb = s->pb;
    AVStream *st;
    uint8_t header[9];

    avio_read(pb, header, 6);

    st = avformat_new_stream(s, NULL);
    if (!st)
    {
        return AVERROR(ENOMEM);
    }
    if(memcmp(header,AMR_header,6)!=0)
    {
        avio_read(pb, header+6, 3);
        if(memcmp(header,AMRWB_header,9)!=0)
        {
            return -1;
        }

        st->codec->codec_tag = MKTAG('s', 'a', 'w', 'b');
        st->codec->codec_id = CODEC_ID_AMR_WB;
        st->codec->sample_rate = 16000;
        st->codec->frame_size = 320;
    }
    else
    {
        st->codec->codec_tag = MKTAG('s', 'a', 'm', 'r');
        st->codec->codec_id = CODEC_ID_AMR_NB;
        st->codec->sample_rate = 8000;
        st->codec->frame_size = 160;
    }
    st->codec->channels = 1;
    st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
    av_set_pts_info(st, 64, 1, st->codec->sample_rate);

    return 0;
}

static int amr_read_packet(AVFormatContext *s,
                          AVPacket *pkt)
{
    AVCodecContext *enc = s->streams[0]->codec;
    int read, size = 0, toc, mode;
    int64_t pos = avio_tell(s->pb);

    if (s->pb->eof_reached)
    {
        return AVERROR(EIO);
    }

//FIXME this is wrong, this should rather be in a AVParset
    toc=avio_r8(s->pb);
    mode = (toc >> 3) & 0x0F;

    if (enc->codec_id == CODEC_ID_AMR_NB)
    {
        static const uint8_t packed_size[16] = {12, 13, 15, 17, 19, 20, 26, 31, 5, 0, 0, 0, 0, 0, 0, 0};

        size=packed_size[mode]+1;
    }
    else if(enc->codec_id == CODEC_ID_AMR_WB)
    {
        static uint8_t packed_size[16] = {18, 24, 33, 37, 41, 47, 51, 59, 61, 6, 6, 0, 0, 0, 1, 1};

        size=packed_size[mode];
    }
    else
    {
        assert(0);
    }

    if ( (size==0) || av_new_packet(pkt, size))
    {
        return AVERROR(EIO);
    }

    /* Both AMR formats have 50 frames per second */
    s->streams[0]->codec->bit_rate = size*8*50;

    pkt->stream_index = 0;
    pkt->pos = pos;
    pkt->data[0]=toc;
    pkt->duration= enc->codec_id == CODEC_ID_AMR_NB ? 160 : 320;
    read = avio_read(s->pb, pkt->data+1, size-1);

    if (read != size-1)
    {
        av_free_packet(pkt);
        return AVERROR(EIO);
    }

    return 0;
}

#if CONFIG_AMR_DEMUXER
AVInputFormat ff_amr_demuxer = {
    .name           = "amr",
    .long_name      = NULL_IF_CONFIG_SMALL("3GPP AMR file format"),
    .read_probe     = amr_probe,
    .read_header    = amr_read_header,
    .read_packet    = amr_read_packet,
    .flags = AVFMT_GENERIC_INDEX,
};
#endif

#if CONFIG_AMR_MUXER
AVOutputFormat ff_amr_muxer = {
    .name              = "amr",
    .long_name         = NULL_IF_CONFIG_SMALL("3GPP AMR file format"),
    .mime_type         = "audio/amr",
    .extensions        = "amr",
    .audio_codec       = CODEC_ID_AMR_NB,
    .video_codec       = CODEC_ID_NONE,
    .write_header      = amr_write_header,
    .write_packet      = amr_write_packet,
};
#endif