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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;
  41. } MaxisXADemuxContext;
  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_EXTENSION;
  63. }
  64.  
  65. static int xa_read_header(AVFormatContext *s)
  66. {
  67.     MaxisXADemuxContext *xa = s->priv_data;
  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.  
  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 */
  86.  
  87.     if (!st->codec->channels || !st->codec->sample_rate)
  88.         return AVERROR_INVALIDDATA;
  89.  
  90.     st->codec->bit_rate = av_clip(15LL * st->codec->channels * 8 *
  91.                                   st->codec->sample_rate / 28, 0, INT_MAX);
  92.  
  93.     avpriv_set_pts_info(st, 64, 1, st->codec->sample_rate);
  94.     st->start_time = 0;
  95.  
  96.     return 0;
  97. }
  98.  
  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. };
  132.