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 Libav.
6  *
7  * Libav 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  * Libav 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 Libav; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
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;
43 
44 static int xa_probe(AVProbeData *p)
45 {
46  int channels, srate, bits_per_sample;
47  if (p->buf_size < 24)
48  return 0;
49  switch(AV_RL32(p->buf)) {
50  case XA00_TAG:
51  case XAI0_TAG:
52  case XAJ0_TAG:
53  break;
54  default:
55  return 0;
56  }
57  channels = AV_RL16(p->buf + 10);
58  srate = AV_RL32(p->buf + 12);
59  bits_per_sample = AV_RL16(p->buf + 22);
60  if (!channels || channels > 8 || !srate || srate > 192000 ||
61  bits_per_sample < 4 || bits_per_sample > 32)
62  return 0;
63  return AVPROBE_SCORE_MAX/2;
64 }
65 
68 {
70  AVIOContext *pb = s->pb;
71  AVStream *st;
72 
73  /*Set up the XA Audio Decoder*/
74  st = avformat_new_stream(s, NULL);
75  if (!st)
76  return AVERROR(ENOMEM);
77 
80  avio_skip(pb, 4); /* Skip the XA ID */
81  xa->out_size = avio_rl32(pb);
82  avio_skip(pb, 2); /* Skip the tag */
83  st->codec->channels = avio_rl16(pb);
84  st->codec->sample_rate = avio_rl32(pb);
85  /* Value in file is average byte rate*/
86  st->codec->bit_rate = avio_rl32(pb) * 8;
87  st->codec->block_align = avio_rl16(pb);
89 
90  avpriv_set_pts_info(st, 64, 1, st->codec->sample_rate);
91 
92  return 0;
93 }
94 
96  AVPacket *pkt)
97 {
99  AVStream *st = s->streams[0];
100  AVIOContext *pb = s->pb;
101  unsigned int packet_size;
102  int ret;
103 
104  if(xa->sent_bytes > xa->out_size)
105  return AVERROR(EIO);
106  /* 1 byte header and 14 bytes worth of samples * number channels per block */
107  packet_size = 15*st->codec->channels;
108 
109  ret = av_get_packet(pb, pkt, packet_size);
110  if(ret < 0)
111  return ret;
112 
113  pkt->stream_index = st->index;
114  xa->sent_bytes += packet_size;
115  pkt->pts = xa->audio_frame_counter;
116  /* 14 bytes Samples per channel with 2 samples per byte */
117  xa->audio_frame_counter += 28 * st->codec->channels;
118 
119  return ret;
120 }
121 
123  .name = "xa",
124  .long_name = NULL_IF_CONFIG_SMALL("Maxis XA File Format"),
125  .priv_data_size = sizeof(MaxisXADemuxContext),
126  .read_probe = xa_probe,
129 };