/* * RAW AC-4 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/avassert.h"#include "libavutil/crc.h"#include "avformat.h"#include "demux.h"#include "rawdec.h" static int ac4_probe(const AVProbeData *p){    const uint8_t *buf = p->buf;    int left = p->buf_size;    int max_frames = 0;     while (left > 7) {        int size;         if (buf[0] == 0xAC &&            (buf[1] == 0x40 ||             buf[1] == 0x41)) {            size = (buf[2] << 8) | buf[3];            if (size == 0xFFFF)                size = 3 + ((buf[4] << 16) | (buf[5] << 8) | buf[6]);            size += 4;            if (buf[1] == 0x41)                size += 2;            if (left < size)                break;            max_frames++;            left -= size;            buf += size;        } else {            break;        }    }     return FFMIN(AVPROBE_SCORE_MAX, max_frames * 7);} static int ac4_read_header(AVFormatContext *s){    AVStream *st;     st = avformat_new_stream(s, NULL);    if (!st)        return AVERROR(ENOMEM);     st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;    st->codecpar->codec_id   = AV_CODEC_ID_AC4;     return 0;} static int ac4_read_packet(AVFormatContext *s, AVPacket *pkt){    AVIOContext *pb = s->pb;    int64_t pos;    uint16_t sync;    int ret, size;     if (avio_feof(s->pb))        return AVERROR_EOF;     pos  = avio_tell(s->pb);    sync = avio_rb16(pb);    size = avio_rb16(pb);    if (size == 0xffff)        size = avio_rb24(pb);     ret = av_get_packet(pb, pkt, size);    pkt->pos = pos;    pkt->stream_index = 0;     if (sync == 0xAC41)        avio_skip(pb, 2);     return ret;} const FFInputFormat ff_ac4_demuxer = {    .p.name         = "ac4",    .p.long_name    = NULL_IF_CONFIG_SMALL("raw AC-4"),    .p.flags        = AVFMT_GENERIC_INDEX,    .p.extensions   = "ac4",    .read_probe     = ac4_probe,    .read_header    = ac4_read_header,    .read_packet    = ac4_read_packet,};