Maxis XA demuxer and decoder.

Patch by Robert Marston rmarston (\at/) gmail point com
Original thread: [FFmpeg-soc] [Patch] Maxis EA XA decoder - GSoC Task
Date: 04/08/2008 01:36 AM

Originally committed as revision 12817 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 116 insertions, 0 deletions

diff --git a/libavformat/xa.c b/libavformat/xa.c
new file mode 100644
index 0000000000..88f731a3da
--- /dev/null
+++ b/libavformat/xa.c
@@ -0,0 +1,116 @@
+/*
+ * Maxis XA (.xa) File Demuxer
+ * Copyright (c) 2008 Robert Marston
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file xa.c
+ * Maxis XA File Demuxer
+ * by Robert Marston (rmarston@gmail.com)
+ * for more information on the XA audio format see
+ *   http://wiki.multimedia.cx/index.php?title=Maxis_XA
+ */
+
+#include "avformat.h"
+
+#define XA00_TAG MKTAG('X', 'A', 0, 0)
+#define XAI0_TAG MKTAG('X', 'A', 'I', 0)
+#define XAJ0_TAG MKTAG('X', 'A', 'J', 0)
+
+typedef struct MaxisXADemuxContext {
+    uint32_t out_size;
+    uint32_t sent_bytes;
+    uint32_t audio_frame_counter;
+} MaxisXADemuxContext;
+
+static int xa_probe(AVProbeData *p)
+{
+    switch(AV_RL32(p->buf)) {
+    case XA00_TAG:
+    case XAI0_TAG:
+    case XAJ0_TAG:
+        return AVPROBE_SCORE_MAX;
+    }
+    return 0;
+}
+
+static int xa_read_header(AVFormatContext *s,
+               AVFormatParameters *ap)
+{
+    MaxisXADemuxContext *xa = s->priv_data;
+    ByteIOContext *pb = s->pb;
+    AVStream *st;
+
+    /*Set up the XA Audio Decoder*/
+    st = av_new_stream(s, 0);
+    if (!st)
+        return AVERROR(ENOMEM);
+
+    st->codec->codec_type   = CODEC_TYPE_AUDIO;
+    st->codec->codec_id     = CODEC_ID_ADPCM_EA_MAXIS_XA;
+    url_fskip(pb, 4);       /* Skip the XA ID */
+    xa->out_size            =  get_le32(pb);
+    url_fskip(pb, 2);       /* Skip the tag */
+    st->codec->channels     = get_le16(pb);
+    st->codec->sample_rate  = get_le32(pb);
+    /* Value in file is average byte rate*/
+    st->codec->bit_rate     = get_le32(pb) * 8;
+    st->codec->block_align  = get_le16(pb);
+    st->codec->bits_per_sample = get_le16(pb);
+
+    av_set_pts_info(st, 64, 1, st->codec->sample_rate);
+
+    return 0;
+}
+
+static int xa_read_packet(AVFormatContext *s,
+                          AVPacket *pkt)
+{
+    MaxisXADemuxContext *xa = s->priv_data;
+    AVStream *st = s->streams[0];
+    ByteIOContext *pb = s->pb;
+    unsigned int packet_size;
+    int ret;
+
+    if(xa->sent_bytes > xa->out_size)
+        return AVERROR(EIO);
+    /* 1 byte header and 14 bytes worth of samples * number channels per block */
+    packet_size = 15*st->codec->channels;
+
+    ret = av_get_packet(pb, pkt, packet_size);
+    if(ret != packet_size)
+        return AVERROR(EIO);
+
+    pkt->stream_index = st->index;
+    xa->sent_bytes += packet_size;
+    pkt->pts = xa->audio_frame_counter;
+    /* 14 bytes Samples per channel with 2 samples per byte */
+    xa->audio_frame_counter += 28 * st->codec->channels;
+
+    return ret;
+}
+
+AVInputFormat xa_demuxer = {
+    "xa",
+    "Maxis XA File Format",
+    sizeof(MaxisXADemuxContext),
+    xa_probe,
+    xa_read_header,
+    xa_read_packet,
+};