FFmpeg/libavformat/amr.c

/* 
 * amr file format
 * Copyright (c) 2001 ffmpeg project
 *
 * This library 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 of the License, or (at your option) any later version.
 *
 * This library 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 this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

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

Only amr narrowband (not amr-wb) is supported for now.

*/
#include "avformat.h"
#include "avi.h"

static const unsigned char AMR_header [] = "#!AMR\n";

/* AMR_FILE header */
static int put_amr_header(ByteIOContext *pb, AVCodecContext *enc)
{
    put_tag(pb, AMR_header);       /* magic number */
    return 0;
}

static int amr_write_header(AVFormatContext *s)
{
    ByteIOContext *pb = &s->pb;

    s->priv_data = NULL;

    /* format header */
    if (put_amr_header(pb, &s->streams[0]->codec) < 0) {
        return -1;
    }

    put_flush_packet(pb);

    return 0;
}

static int amr_write_packet(AVFormatContext *s, int stream_index_ptr,
                           uint8_t *buf, int size, int force_pts)
{
    put_buffer(&s->pb, buf, size);
    put_flush_packet(&s->pb);
    return 0;
}

static int amr_write_trailer(AVFormatContext *s)
{
    return 0;
}

static int amr_probe(AVProbeData *p)
{
    /* check file header */
    if (p->buf_size < 6)
        return 0;
    if(memcmp(p->buf,AMR_header,6)==0)
        return AVPROBE_SCORE_MAX;
    else
        return 0;
}

/* amr input */
static int amr_read_header(AVFormatContext *s,
                           AVFormatParameters *ap)
{
    ByteIOContext *pb = &s->pb;
    AVStream *st;
    u_int8_t header[6];

    get_buffer(pb, header, 6);

    if(memcmp(header,AMR_header,6)!=0)
    {
        return -1;
    }

    st = av_new_stream(s, 0);
    if (!st)
        return AVERROR_NOMEM;

    st->codec.codec_type = CODEC_TYPE_AUDIO;
    st->codec.codec_tag = CODEC_ID_AMR_NB;
    st->codec.codec_id = CODEC_ID_AMR_NB;
    st->codec.channels = 1;
    st->codec.sample_rate = 8000;
    return 0;
}

#define MAX_SIZE 32

static int amr_read_packet(AVFormatContext *s,
                          AVPacket *pkt)
{
    static u_int16_t packed_size[16] = {12, 13, 15, 17, 19, 20, 26, 31, 5, 0, 0, 0, 0, 0, 0, 0};
    u_int8_t toc, q, ft;
    int read;
    int size;

    if (url_feof(&s->pb))
        return -EIO;

    toc=0;

    toc=get_byte(&s->pb);

    q  = (toc >> 2) & 0x01;
    ft = (toc >> 3) & 0x0F;

    size=packed_size[ft];
    //printf("amr_read_packet size=%d\n",size);

    if (av_new_packet(pkt, size+1))
        return -EIO;
    pkt->stream_index = 0;
    
    pkt->data[0]=toc;

    read = get_buffer(&s->pb, pkt->data+1, size);

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

    return 0;
}

static int amr_read_close(AVFormatContext *s)
{
    return 0;
}

static AVInputFormat amr_iformat = {
    "amr",
    "3gpp amr file format",
    0,
    amr_probe,
    amr_read_header,
    amr_read_packet,
    amr_read_close,
};

static AVOutputFormat amr_oformat = {
    "amr",
    "3gpp amr file format",
    "audio/amr",
    "amr",
    0,
    CODEC_ID_AMR_NB,
    CODEC_ID_NONE,
    amr_write_header,
    amr_write_packet,
    amr_write_trailer,
};

int amr_init(void)
{
    av_register_input_format(&amr_iformat);
    av_register_output_format(&amr_oformat);
    return 0;
}