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xa.c
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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
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 "libavutil/intreadwrite.h"
31 #include "avformat.h"
32 #include "internal.h"
33 
34 #define XA00_TAG MKTAG('X', 'A', 0, 0)
35 #define XAI0_TAG MKTAG('X', 'A', 'I', 0)
36 #define XAJ0_TAG MKTAG('X', 'A', 'J', 0)
37 
38 typedef struct MaxisXADemuxContext {
39  uint32_t out_size;
40  uint32_t sent_bytes;
42 
43 static int xa_probe(AVProbeData *p)
44 {
45  int channels, srate, bits_per_sample;
46  if (p->buf_size < 24)
47  return 0;
48  switch(AV_RL32(p->buf)) {
49  case XA00_TAG:
50  case XAI0_TAG:
51  case XAJ0_TAG:
52  break;
53  default:
54  return 0;
55  }
56  channels = AV_RL16(p->buf + 10);
57  srate = AV_RL32(p->buf + 12);
58  bits_per_sample = AV_RL16(p->buf + 22);
59  if (!channels || channels > 8 || !srate || srate > 192000 ||
60  bits_per_sample < 4 || bits_per_sample > 32)
61  return 0;
62  return AVPROBE_SCORE_MAX/2;
63 }
64 
66 {
68  AVIOContext *pb = s->pb;
69  AVStream *st;
70 
71  /*Set up the XA Audio Decoder*/
72  st = avformat_new_stream(s, NULL);
73  if (!st)
74  return AVERROR(ENOMEM);
75 
78  avio_skip(pb, 4); /* Skip the XA ID */
79  xa->out_size = avio_rl32(pb);
80  avio_skip(pb, 2); /* Skip the tag */
81  st->codec->channels = avio_rl16(pb);
82  st->codec->sample_rate = avio_rl32(pb);
83  avio_skip(pb, 4); /* Skip average byte rate */
84  avio_skip(pb, 2); /* Skip block align */
85  avio_skip(pb, 2); /* Skip bits-per-sample */
86 
87  st->codec->bit_rate = av_clip(15LL * st->codec->channels * 8 *
88  st->codec->sample_rate / 28, 0, INT_MAX);
89 
90  avpriv_set_pts_info(st, 64, 1, st->codec->sample_rate);
91  st->start_time = 0;
92 
93  return 0;
94 }
95 
97  AVPacket *pkt)
98 {
100  AVStream *st = s->streams[0];
101  AVIOContext *pb = s->pb;
102  unsigned int packet_size;
103  int ret;
104 
105  if (xa->sent_bytes >= xa->out_size)
106  return AVERROR_EOF;
107  /* 1 byte header and 14 bytes worth of samples * number channels per block */
108  packet_size = 15*st->codec->channels;
109 
110  ret = av_get_packet(pb, pkt, packet_size);
111  if(ret < 0)
112  return ret;
113 
114  pkt->stream_index = st->index;
115  xa->sent_bytes += packet_size;
116  pkt->duration = 28;
117 
118  return ret;
119 }
120 
122  .name = "xa",
123  .long_name = NULL_IF_CONFIG_SMALL("Maxis XA"),
124  .priv_data_size = sizeof(MaxisXADemuxContext),
125  .read_probe = xa_probe,
128 };