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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     switch(AV_RL32(p->buf)) {
00046     case XA00_TAG:
00047     case XAI0_TAG:
00048     case XAJ0_TAG:
00049         return AVPROBE_SCORE_MAX;
00050     }
00051     return 0;
00052 }
00053 
00054 static int xa_read_header(AVFormatContext *s,
00055                AVFormatParameters *ap)
00056 {
00057     MaxisXADemuxContext *xa = s->priv_data;
00058     ByteIOContext *pb = s->pb;
00059     AVStream *st;
00060 
00061     /*Set up the XA Audio Decoder*/
00062     st = av_new_stream(s, 0);
00063     if (!st)
00064         return AVERROR(ENOMEM);
00065 
00066     st->codec->codec_type   = CODEC_TYPE_AUDIO;
00067     st->codec->codec_id     = CODEC_ID_ADPCM_EA_MAXIS_XA;
00068     url_fskip(pb, 4);       /* Skip the XA ID */
00069     xa->out_size            =  get_le32(pb);
00070     url_fskip(pb, 2);       /* Skip the tag */
00071     st->codec->channels     = get_le16(pb);
00072     st->codec->sample_rate  = get_le32(pb);
00073     /* Value in file is average byte rate*/
00074     st->codec->bit_rate     = get_le32(pb) * 8;
00075     st->codec->block_align  = get_le16(pb);
00076     st->codec->bits_per_coded_sample = get_le16(pb);
00077 
00078     av_set_pts_info(st, 64, 1, st->codec->sample_rate);
00079 
00080     return 0;
00081 }
00082 
00083 static int xa_read_packet(AVFormatContext *s,
00084                           AVPacket *pkt)
00085 {
00086     MaxisXADemuxContext *xa = s->priv_data;
00087     AVStream *st = s->streams[0];
00088     ByteIOContext *pb = s->pb;
00089     unsigned int packet_size;
00090     int ret;
00091 
00092     if(xa->sent_bytes > xa->out_size)
00093         return AVERROR(EIO);
00094     /* 1 byte header and 14 bytes worth of samples * number channels per block */
00095     packet_size = 15*st->codec->channels;
00096 
00097     ret = av_get_packet(pb, pkt, packet_size);
00098     if(ret != packet_size)
00099         return AVERROR(EIO);
00100 
00101     pkt->stream_index = st->index;
00102     xa->sent_bytes += packet_size;
00103     pkt->pts = xa->audio_frame_counter;
00104     /* 14 bytes Samples per channel with 2 samples per byte */
00105     xa->audio_frame_counter += 28 * st->codec->channels;
00106 
00107     return ret;
00108 }
00109 
00110 AVInputFormat xa_demuxer = {
00111     "xa",
00112     NULL_IF_CONFIG_SMALL("Maxis XA File Format"),
00113     sizeof(MaxisXADemuxContext),
00114     xa_probe,
00115     xa_read_header,
00116     xa_read_packet,
00117 };

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