libavformat/xa.c

   1 /*
   2  * Maxis XA (.xa) File Demuxer
   3  * Copyright (c) 2008 Robert Marston
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file xa.c
  24  * Maxis XA File Demuxer
  25  * by Robert Marston (rmarston@gmail.com)
  26  * for more information on the XA audio format see
  27  *   http://wiki.multimedia.cx/index.php?title=Maxis_XA
  28  */
  29
  30 #include "avformat.h"
  31
  32 #define XA00_TAG MKTAG('X', 'A', 0, 0)
  33 #define XAI0_TAG MKTAG('X', 'A', 'I', 0)
  34 #define XAJ0_TAG MKTAG('X', 'A', 'J', 0)
  35
  36 typedef struct MaxisXADemuxContext {
  37     uint32_t out_size;
  38     uint32_t sent_bytes;
  39     uint32_t audio_frame_counter;
  40 } MaxisXADemuxContext;
  41
  42 static int xa_probe(AVProbeData *p)
  43 {
  44     switch(AV_RL32(p->buf)) {
  45     case XA00_TAG:
  46     case XAI0_TAG:
  47     case XAJ0_TAG:
  48         return AVPROBE_SCORE_MAX;
  49     }
  50     return 0;
  51 }
  52
  53 static int xa_read_header(AVFormatContext *s,
  54                AVFormatParameters *ap)
  55 {
  56     MaxisXADemuxContext *xa = s->priv_data;
  57     ByteIOContext *pb = s->pb;
  58     AVStream *st;
  59
  60     /*Set up the XA Audio Decoder*/
  61     st = av_new_stream(s, 0);
  62     if (!st)
  63         return AVERROR(ENOMEM);
  64
  65     st->codec->codec_type   = CODEC_TYPE_AUDIO;
  66     st->codec->codec_id     = CODEC_ID_ADPCM_EA_MAXIS_XA;
  67     url_fskip(pb, 4);       /* Skip the XA ID */
  68     xa->out_size            =  get_le32(pb);
  69     url_fskip(pb, 2);       /* Skip the tag */
  70     st->codec->channels     = get_le16(pb);
  71     st->codec->sample_rate  = get_le32(pb);
  72     /* Value in file is average byte rate*/
  73     st->codec->bit_rate     = get_le32(pb) * 8;
  74     st->codec->block_align  = get_le16(pb);
  75     st->codec->bits_per_coded_sample = get_le16(pb);
  76
  77     av_set_pts_info(st, 64, 1, st->codec->sample_rate);
  78
  79     return 0;
  80 }
  81
  82 static int xa_read_packet(AVFormatContext *s,
  83                           AVPacket *pkt)
  84 {
  85     MaxisXADemuxContext *xa = s->priv_data;
  86     AVStream *st = s->streams[0];
  87     ByteIOContext *pb = s->pb;
  88     unsigned int packet_size;
  89     int ret;
  90
  91     if(xa->sent_bytes > xa->out_size)
  92         return AVERROR(EIO);
  93     /* 1 byte header and 14 bytes worth of samples * number channels per block */
  94     packet_size = 15*st->codec->channels;
  95
  96     ret = av_get_packet(pb, pkt, packet_size);
  97     if(ret != packet_size)
  98         return AVERROR(EIO);
  99
 100     pkt->stream_index = st->index;
 101     xa->sent_bytes += packet_size;
 102     pkt->pts = xa->audio_frame_counter;
 103     /* 14 bytes Samples per channel with 2 samples per byte */
 104     xa->audio_frame_counter += 28 * st->codec->channels;
 105
 106     return ret;
 107 }
 108
 109 AVInputFormat xa_demuxer = {
 110     "xa",
 111     NULL_IF_CONFIG_SMALL("Maxis XA File Format"),
 112     sizeof(MaxisXADemuxContext),
 113     xa_probe,
 114     xa_read_header,
 115     xa_read_packet,
 116 };