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ffmpeg / libavformat / xa.c @ d7fb5a18

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/*
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 * Maxis XA (.xa) File Demuxer
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 * Copyright (c) 2008 Robert Marston
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 *
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 * This file is part of FFmpeg.
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 *
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 * 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
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 * 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
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * 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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 */
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/**
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 * @file xa.c
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 * Maxis XA File Demuxer
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 * by Robert Marston (rmarston@gmail.com)
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 * for more information on the XA audio format see
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 *   http://wiki.multimedia.cx/index.php?title=Maxis_XA
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 */
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#include "avformat.h"
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#define XA00_TAG MKTAG('X', 'A', 0, 0)
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#define XAI0_TAG MKTAG('X', 'A', 'I', 0)
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#define XAJ0_TAG MKTAG('X', 'A', 'J', 0)
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typedef struct MaxisXADemuxContext {
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    uint32_t out_size;
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    uint32_t sent_bytes;
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    uint32_t audio_frame_counter;
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} MaxisXADemuxContext;
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static int xa_probe(AVProbeData *p)
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{
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    switch(AV_RL32(p->buf)) {
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    case XA00_TAG:
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    case XAI0_TAG:
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    case XAJ0_TAG:
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        return AVPROBE_SCORE_MAX;
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    }
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    return 0;
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}
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static int xa_read_header(AVFormatContext *s,
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               AVFormatParameters *ap)
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{
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    MaxisXADemuxContext *xa = s->priv_data;
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    ByteIOContext *pb = s->pb;
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    AVStream *st;
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    /*Set up the XA Audio Decoder*/
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    st = av_new_stream(s, 0);
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    if (!st)
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        return AVERROR(ENOMEM);
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    st->codec->codec_type   = CODEC_TYPE_AUDIO;
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    st->codec->codec_id     = CODEC_ID_ADPCM_EA_MAXIS_XA;
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    url_fskip(pb, 4);       /* Skip the XA ID */
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    xa->out_size            =  get_le32(pb);
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    url_fskip(pb, 2);       /* Skip the tag */
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    st->codec->channels     = get_le16(pb);
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    st->codec->sample_rate  = get_le32(pb);
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    /* Value in file is average byte rate*/
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    st->codec->bit_rate     = get_le32(pb) * 8;
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    st->codec->block_align  = get_le16(pb);
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    st->codec->bits_per_coded_sample = get_le16(pb);
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    av_set_pts_info(st, 64, 1, st->codec->sample_rate);
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    return 0;
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}
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static int xa_read_packet(AVFormatContext *s,
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                          AVPacket *pkt)
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{
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    MaxisXADemuxContext *xa = s->priv_data;
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    AVStream *st = s->streams[0];
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    ByteIOContext *pb = s->pb;
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    unsigned int packet_size;
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    int ret;
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    if(xa->sent_bytes > xa->out_size)
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        return AVERROR(EIO);
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    /* 1 byte header and 14 bytes worth of samples * number channels per block */
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    packet_size = 15*st->codec->channels;
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    ret = av_get_packet(pb, pkt, packet_size);
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    if(ret != packet_size)
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        return AVERROR(EIO);
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    pkt->stream_index = st->index;
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    xa->sent_bytes += packet_size;
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    pkt->pts = xa->audio_frame_counter;
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    /* 14 bytes Samples per channel with 2 samples per byte */
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    xa->audio_frame_counter += 28 * st->codec->channels;
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    return ret;
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}
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AVInputFormat xa_demuxer = {
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    "xa",
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    NULL_IF_CONFIG_SMALL("Maxis XA File Format"),
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    sizeof(MaxisXADemuxContext),
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    xa_probe,
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    xa_read_header,
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    xa_read_packet,
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};