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libavformat/xa.c

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00001 /*
00002  * Maxis XA (.xa) File Demuxer
00003  * Copyright (c) 2008 Robert Marston
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * FFmpeg is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00030 #include "libavutil/intreadwrite.h"
00031 #include "avformat.h"
00032 
00033 #define XA00_TAG MKTAG('X', 'A', 0, 0)
00034 #define XAI0_TAG MKTAG('X', 'A', 'I', 0)
00035 #define XAJ0_TAG MKTAG('X', 'A', 'J', 0)
00036 
00037 typedef struct MaxisXADemuxContext {
00038     uint32_t out_size;
00039     uint32_t sent_bytes;
00040     uint32_t audio_frame_counter;
00041 } MaxisXADemuxContext;
00042 
00043 static int xa_probe(AVProbeData *p)
00044 {
00045     int channels, srate, bits_per_sample;
00046     if (p->buf_size < 24)
00047         return 0;
00048     switch(AV_RL32(p->buf)) {
00049     case XA00_TAG:
00050     case XAI0_TAG:
00051     case XAJ0_TAG:
00052         break;
00053     default:
00054         return 0;
00055     }
00056     channels        = AV_RL16(p->buf + 10);
00057     srate           = AV_RL32(p->buf + 12);
00058     bits_per_sample = AV_RL16(p->buf + 22);
00059     if (!channels || channels > 8 || !srate || srate > 192000 ||
00060         bits_per_sample < 4 || bits_per_sample > 32)
00061         return 0;
00062     return AVPROBE_SCORE_MAX/2;
00063 }
00064 
00065 static int xa_read_header(AVFormatContext *s,
00066                AVFormatParameters *ap)
00067 {
00068     MaxisXADemuxContext *xa = s->priv_data;
00069     ByteIOContext *pb = s->pb;
00070     AVStream *st;
00071 
00072     /*Set up the XA Audio Decoder*/
00073     st = av_new_stream(s, 0);
00074     if (!st)
00075         return AVERROR(ENOMEM);
00076 
00077     st->codec->codec_type   = AVMEDIA_TYPE_AUDIO;
00078     st->codec->codec_id     = CODEC_ID_ADPCM_EA_MAXIS_XA;
00079     url_fskip(pb, 4);       /* Skip the XA ID */
00080     xa->out_size            =  get_le32(pb);
00081     url_fskip(pb, 2);       /* Skip the tag */
00082     st->codec->channels     = get_le16(pb);
00083     st->codec->sample_rate  = get_le32(pb);
00084     /* Value in file is average byte rate*/
00085     st->codec->bit_rate     = get_le32(pb) * 8;
00086     st->codec->block_align  = get_le16(pb);
00087     st->codec->bits_per_coded_sample = get_le16(pb);
00088 
00089     av_set_pts_info(st, 64, 1, st->codec->sample_rate);
00090 
00091     return 0;
00092 }
00093 
00094 static int xa_read_packet(AVFormatContext *s,
00095                           AVPacket *pkt)
00096 {
00097     MaxisXADemuxContext *xa = s->priv_data;
00098     AVStream *st = s->streams[0];
00099     ByteIOContext *pb = s->pb;
00100     unsigned int packet_size;
00101     int ret;
00102 
00103     if(xa->sent_bytes > xa->out_size)
00104         return AVERROR(EIO);
00105     /* 1 byte header and 14 bytes worth of samples * number channels per block */
00106     packet_size = 15*st->codec->channels;
00107 
00108     ret = av_get_packet(pb, pkt, packet_size);
00109     if(ret < 0)
00110         return ret;
00111 
00112     pkt->stream_index = st->index;
00113     xa->sent_bytes += packet_size;
00114     pkt->pts = xa->audio_frame_counter;
00115     /* 14 bytes Samples per channel with 2 samples per byte */
00116     xa->audio_frame_counter += 28 * st->codec->channels;
00117 
00118     return ret;
00119 }
00120 
00121 AVInputFormat xa_demuxer = {
00122     "xa",
00123     NULL_IF_CONFIG_SMALL("Maxis XA File Format"),
00124     sizeof(MaxisXADemuxContext),
00125     xa_probe,
00126     xa_read_header,
00127     xa_read_packet,
00128 };

Generated on Fri Sep 16 2011 17:17:51 for FFmpeg by  doxygen 1.7.1