FFmpeg: libavformat/xa.c Source File

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libavformat

xa.c

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1 /*

2 * Maxis XA (.xa) File Demuxer

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 */

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 */

30 #include "libavutil/intreadwrite.h"

31 #include "avformat.h"

32 #include "internal.h"

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)

38 typedef struct MaxisXADemuxContext {

39 uint32_t out_size;

40 uint32_t sent_bytes;

41 } MaxisXADemuxContext;

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_EXTENSION;

63 }

65 static int xa_read_header(AVFormatContext *s)

66 {

67 MaxisXADemuxContext *xa = s->priv_data;

68 AVIOContext *pb = s->pb;

69 AVStream *st;

71 /*Set up the XA Audio Decoder*/

72 st = avformat_new_stream(s, NULL);

73 if (!st)

74 return AVERROR(ENOMEM);

76 st->codec->codec_type = AVMEDIA_TYPE_AUDIO;

77 st->codec->codec_id = AV_CODEC_ID_ADPCM_EA_MAXIS_XA;

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 */

87 if (!st->codec->channels || !st->codec->sample_rate)

88 return AVERROR_INVALIDDATA;

90 st->codec->bit_rate = av_clip(15LL * st->codec->channels * 8 *

91 st->codec->sample_rate / 28, 0, INT_MAX);

93 avpriv_set_pts_info(st, 64, 1, st->codec->sample_rate);

94 st->start_time = 0;

96 return 0;

97 }

99 static int xa_read_packet(AVFormatContext *s,

100 AVPacket *pkt)

101 {

102 MaxisXADemuxContext *xa = s->priv_data;

103 AVStream *st = s->streams[0];

104 AVIOContext *pb = s->pb;

105 unsigned int packet_size;

106 int ret;

107

108 if (xa->sent_bytes >= xa->out_size)

109 return AVERROR_EOF;

110 /* 1 byte header and 14 bytes worth of samples * number channels per block */

111 packet_size = 15*st->codec->channels;

112

113 ret = av_get_packet(pb, pkt, packet_size);

114 if(ret < 0)

115 return ret;

116

117 pkt->stream_index = st->index;

118 xa->sent_bytes += packet_size;

119 pkt->duration = 28;

120

121 return ret;

122 }

123

124 AVInputFormat ff_xa_demuxer = {

125 .name = "xa",

126 .long_name = NULL_IF_CONFIG_SMALL("Maxis XA"),

127 .priv_data_size = sizeof(MaxisXADemuxContext),

128 .read_probe = xa_probe,

129 .read_header = xa_read_header,

130 .read_packet = xa_read_packet,

131 };

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