amr.c 5.37 KB
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/*
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 * amr file format
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 * Copyright (c) 2001 FFmpeg project
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 *
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 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * 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
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */

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

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Only mono files are supported.
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*/
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#include "libavutil/channel_layout.h"
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#include "avformat.h"
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#include "internal.h"
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typedef struct {
    uint64_t cumulated_size;
    uint64_t block_count;
} AMRContext;

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static const char AMR_header[]   = "#!AMR\n";
static const char AMRWB_header[] = "#!AMR-WB\n";
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#if CONFIG_AMR_MUXER
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static int amr_write_header(AVFormatContext *s)
{
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    AVIOContext    *pb  = s->pb;
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    AVCodecParameters *par = s->streams[0]->codecpar;
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    s->priv_data = NULL;

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

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static int amr_write_packet(AVFormatContext *s, AVPacket *pkt)
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{
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    avio_write(s->pb, pkt->data, pkt->size);
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    return 0;
}
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#endif /* CONFIG_AMR_MUXER */
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static int amr_probe(AVProbeData *p)
{
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    // 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)
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    if (!memcmp(p->buf, AMR_header, 5))
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        return AVPROBE_SCORE_MAX;
    else
        return 0;
}

/* amr input */
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static int amr_read_header(AVFormatContext *s)
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{
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    AVIOContext *pb = s->pb;
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    AVStream *st;
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    uint8_t header[9];
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    avio_read(pb, header, 6);
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    st = avformat_new_stream(s, NULL);
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    if (!st)
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        return AVERROR(ENOMEM);
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    if (memcmp(header, AMR_header, 6)) {
        avio_read(pb, header + 6, 3);
        if (memcmp(header, AMRWB_header, 9)) {
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            return -1;
        }
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        st->codecpar->codec_tag   = MKTAG('s', 'a', 'w', 'b');
        st->codecpar->codec_id    = AV_CODEC_ID_AMR_WB;
        st->codecpar->sample_rate = 16000;
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    } else {
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        st->codecpar->codec_tag   = MKTAG('s', 'a', 'm', 'r');
        st->codecpar->codec_id    = AV_CODEC_ID_AMR_NB;
        st->codecpar->sample_rate = 8000;
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    }
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    st->codecpar->channels   = 1;
    st->codecpar->channel_layout = AV_CH_LAYOUT_MONO;
    st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
    avpriv_set_pts_info(st, 64, 1, st->codecpar->sample_rate);
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    return 0;
}

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static int amr_read_packet(AVFormatContext *s, AVPacket *pkt)
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{
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    AVCodecParameters *par = s->streams[0]->codecpar;
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    int read, size = 0, toc, mode;
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    int64_t pos = avio_tell(s->pb);
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    AMRContext *amr = s->priv_data;
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    if (avio_feof(s->pb)) {
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        return AVERROR(EIO);
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    }
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    // FIXME this is wrong, this should rather be in an AVParser
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    toc  = avio_r8(s->pb);
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    mode = (toc >> 3) & 0x0F;
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    if (par->codec_id == AV_CODEC_ID_AMR_NB) {
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        static const uint8_t packed_size[16] = {
            12, 13, 15, 17, 19, 20, 26, 31, 5, 0, 0, 0, 0, 0, 0, 0
        };
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        size = packed_size[mode] + 1;
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    } else if (par->codec_id == AV_CODEC_ID_AMR_WB) {
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        static const uint8_t packed_size[16] = {
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            18, 24, 33, 37, 41, 47, 51, 59, 61, 6, 6, 0, 0, 0, 1, 1
        };
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        size = packed_size[mode];
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    }
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    if (!size || av_new_packet(pkt, size))
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        return AVERROR(EIO);
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    if (amr->cumulated_size < UINT64_MAX - size) {
        amr->cumulated_size += size;
        /* Both AMR formats have 50 frames per second */
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        s->streams[0]->codecpar->bit_rate = amr->cumulated_size / ++amr->block_count * 8 * 50;
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    }
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    pkt->stream_index = 0;
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    pkt->pos          = pos;
    pkt->data[0]      = toc;
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    pkt->duration     = par->codec_id == AV_CODEC_ID_AMR_NB ? 160 : 320;
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    read              = avio_read(s->pb, pkt->data + 1, size - 1);
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    if (read != size - 1) {
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        av_packet_unref(pkt);
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        return AVERROR(EIO);
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    }

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    return 0;
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}

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#if CONFIG_AMR_DEMUXER
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AVInputFormat ff_amr_demuxer = {
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    .name           = "amr",
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    .long_name      = NULL_IF_CONFIG_SMALL("3GPP AMR"),
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    .priv_data_size = sizeof(AMRContext),
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    .read_probe     = amr_probe,
    .read_header    = amr_read_header,
    .read_packet    = amr_read_packet,
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    .flags          = AVFMT_GENERIC_INDEX,
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};
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#endif
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#if CONFIG_AMR_MUXER
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AVOutputFormat ff_amr_muxer = {
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    .name              = "amr",
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    .long_name         = NULL_IF_CONFIG_SMALL("3GPP AMR"),
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    .mime_type         = "audio/amr",
    .extensions        = "amr",
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    .audio_codec       = AV_CODEC_ID_AMR_NB,
    .video_codec       = AV_CODEC_ID_NONE,
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    .write_header      = amr_write_header,
    .write_packet      = amr_write_packet,
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    .flags             = AVFMT_NOTIMESTAMPS,
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};
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#endif