hcom.c

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/*
 * HCOM demuxer
 * Copyright (c) 2019 Paul B Mahol
 *
 * 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 "libavutil/intreadwrite.h"
#include "avformat.h"
#include "demux.h"
#include "internal.h"
#include "pcm.h"
 
static int hcom_probe(const AVProbeData *p)
{
    if (p->buf_size < 132)
        return 0;
    if (!memcmp(p->buf+65, "FSSD", 4) &&
        !memcmp(p->buf+128, "HCOM", 4))
        return AVPROBE_SCORE_MAX;
    return 0;
}
 
static int hcom_read_header(AVFormatContext *s)
{
    AVStream *st;
    av_unused unsigned data_size, rsrc_size, huffcount;
    unsigned compresstype, divisor;
    unsigned dict_entries;
    int ret;
 
    avio_skip(s->pb, 83);
    data_size = avio_rb32(s->pb);
    rsrc_size = avio_rb32(s->pb);
    avio_skip(s->pb, 128-91+4);
    huffcount = avio_rb32(s->pb);
    avio_skip(s->pb, 4);
    compresstype = avio_rb32(s->pb);
    if (compresstype > 1)
        return AVERROR_INVALIDDATA;
    divisor = avio_rb32(s->pb);
    if (divisor == 0 || divisor > 4)
        return AVERROR_INVALIDDATA;
    dict_entries = avio_rb16(s->pb);
 
    st = avformat_new_stream(s, NULL);
    if (!st)
        return AVERROR(ENOMEM);
 
    st->codecpar->codec_type  = AVMEDIA_TYPE_AUDIO;
    st->codecpar->ch_layout.nb_channels = 1;
    st->codecpar->sample_rate = 22050 / divisor;
    st->codecpar->codec_id    = AV_CODEC_ID_HCOM;
    st->codecpar->bits_per_coded_sample = 8;
    st->codecpar->block_align = 4;
 
    ret = ff_alloc_extradata(st->codecpar, dict_entries * 4 + 7);
    if (ret < 0)
        return ret;
    AV_WB16(st->codecpar->extradata, dict_entries);
    AV_WB32(st->codecpar->extradata + 2, compresstype);
    avio_read(s->pb, st->codecpar->extradata + 6, dict_entries * 4);
    avio_skip(s->pb, 1);
    st->codecpar->extradata[dict_entries * 4 + 6] = avio_r8(s->pb);
 
    avpriv_set_pts_info(st, 64, 1, st->codecpar->sample_rate);
 
    return 0;
}
 
const FFInputFormat ff_hcom_demuxer = {
    .p.name         = "hcom",
    .p.long_name    = NULL_IF_CONFIG_SMALL("Macintosh HCOM"),
    .read_probe     = hcom_probe,
    .read_header    = hcom_read_header,
    .read_packet    = ff_pcm_read_packet,
};