libavformat/4xm.c - nest-android-app/ffmpeg - Git at Google

 /*
  * 4X Technologies .4xm File Demuxer (no muxer)
  * Copyright (c) 2003  The FFmpeg Project
  *
  * 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
  * 4X Technologies file demuxer
  * by Mike Melanson (melanson@pcisys.net)
  * for more information on the .4xm file format, visit:
  *   http://www.pcisys.net/~melanson/codecs/
  */

 #include "libavutil/intreadwrite.h"
 #include "libavutil/intfloat.h"
 #include "avformat.h"
 #include "internal.h"

 #define     RIFF_TAG MKTAG('R', 'I', 'F', 'F')
 #define  FOURXMV_TAG MKTAG('4', 'X', 'M', 'V')
 #define     LIST_TAG MKTAG('L', 'I', 'S', 'T')
 #define     HEAD_TAG MKTAG('H', 'E', 'A', 'D')
 #define     TRK__TAG MKTAG('T', 'R', 'K', '_')
 #define     MOVI_TAG MKTAG('M', 'O', 'V', 'I')
 #define     VTRK_TAG MKTAG('V', 'T', 'R', 'K')
 #define     STRK_TAG MKTAG('S', 'T', 'R', 'K')
 #define     std__TAG MKTAG('s', 't', 'd', '_')
 #define     name_TAG MKTAG('n', 'a', 'm', 'e')
 #define     vtrk_TAG MKTAG('v', 't', 'r', 'k')
 #define     strk_TAG MKTAG('s', 't', 'r', 'k')
 #define     ifrm_TAG MKTAG('i', 'f', 'r', 'm')
 #define     pfrm_TAG MKTAG('p', 'f', 'r', 'm')
 #define     cfrm_TAG MKTAG('c', 'f', 'r', 'm')
 #define     ifr2_TAG MKTAG('i', 'f', 'r', '2')
 #define     pfr2_TAG MKTAG('p', 'f', 'r', '2')
 #define     cfr2_TAG MKTAG('c', 'f', 'r', '2')
 #define     snd__TAG MKTAG('s', 'n', 'd', '_')

 #define vtrk_SIZE 0x44
 #define strk_SIZE 0x28

 #define GET_LIST_HEADER() \
     fourcc_tag = avio_rl32(pb); \
     size       = avio_rl32(pb); \
     if (fourcc_tag != LIST_TAG) \
         return AVERROR_INVALIDDATA; \
     fourcc_tag = avio_rl32(pb);

 typedef struct AudioTrack {
     int sample_rate;
     int bits;
     int channels;
     int stream_index;
     int adpcm;
     int64_t audio_pts;
 } AudioTrack;

 typedef struct FourxmDemuxContext {
     int video_stream_index;
     int track_count;
     AudioTrack *tracks;

     int64_t video_pts;
     AVRational fps;
 } FourxmDemuxContext;

 static int fourxm_probe(AVProbeData *p)
 {
     if ((AV_RL32(&p->buf[0]) != RIFF_TAG) ||
         (AV_RL32(&p->buf[8]) != FOURXMV_TAG))
         return 0;

     return AVPROBE_SCORE_MAX;
 }

 static int parse_vtrk(AVFormatContext *s,
                       FourxmDemuxContext *fourxm, uint8_t *buf, int size,
                       int left)
 {
     AVStream *st;
     /* check that there is enough data */
     if (size != vtrk_SIZE || left < size + 8) {
         return AVERROR_INVALIDDATA;
     }

     /* allocate a new AVStream */
     st = avformat_new_stream(s, NULL);
     if (!st)
         return AVERROR(ENOMEM);

     avpriv_set_pts_info(st, 60, fourxm->fps.den, fourxm->fps.num);

     fourxm->video_stream_index = st->index;

     st->codec->codec_type     = AVMEDIA_TYPE_VIDEO;
     st->codec->codec_id       = AV_CODEC_ID_4XM;

     st->codec->extradata      = av_mallocz(4 + AV_INPUT_BUFFER_PADDING_SIZE);
     if (!st->codec->extradata)
         return AVERROR(ENOMEM);
     st->codec->extradata_size = 4;
     AV_WL32(st->codec->extradata, AV_RL32(buf + 16));
     st->codec->width  = AV_RL32(buf + 36);
     st->codec->height = AV_RL32(buf + 40);

     return 0;
 }


 static int parse_strk(AVFormatContext *s,
                       FourxmDemuxContext *fourxm, uint8_t *buf, int size,
                       int left)
 {
     AVStream *st;
     int track;
     /* check that there is enough data */
     if (size != strk_SIZE || left < size + 8)
         return AVERROR_INVALIDDATA;

     track = AV_RL32(buf + 8);
     if ((unsigned)track >= UINT_MAX / sizeof(AudioTrack) - 1) {
         av_log(s, AV_LOG_ERROR, "current_track too large\n");
         return AVERROR_INVALIDDATA;
     }

     if (track + 1 > fourxm->track_count) {
         if (av_reallocp_array(&fourxm->tracks, track + 1, sizeof(AudioTrack)))
             return AVERROR(ENOMEM);
         memset(&fourxm->tracks[fourxm->track_count], 0,
                sizeof(AudioTrack) * (track + 1 - fourxm->track_count));
         fourxm->track_count = track + 1;
     }
     fourxm->tracks[track].adpcm       = AV_RL32(buf + 12);
     fourxm->tracks[track].channels    = AV_RL32(buf + 36);
     fourxm->tracks[track].sample_rate = AV_RL32(buf + 40);
     fourxm->tracks[track].bits        = AV_RL32(buf + 44);
     fourxm->tracks[track].audio_pts   = 0;

     if (fourxm->tracks[track].channels    <= 0 ||
         fourxm->tracks[track].sample_rate <= 0 ||
         fourxm->tracks[track].bits        <= 0) {
         av_log(s, AV_LOG_ERROR, "audio header invalid\n");
         return AVERROR_INVALIDDATA;
     }
     if (!fourxm->tracks[track].adpcm && fourxm->tracks[track].bits<8) {
         av_log(s, AV_LOG_ERROR, "bits unspecified for non ADPCM\n");
         return AVERROR_INVALIDDATA;
     }

     /* allocate a new AVStream */
     st = avformat_new_stream(s, NULL);
     if (!st)
         return AVERROR(ENOMEM);

     st->id = track;
     avpriv_set_pts_info(st, 60, 1, fourxm->tracks[track].sample_rate);

     fourxm->tracks[track].stream_index = st->index;

     st->codec->codec_type            = AVMEDIA_TYPE_AUDIO;
     st->codec->codec_tag             = 0;
     st->codec->channels              = fourxm->tracks[track].channels;
     st->codec->sample_rate           = fourxm->tracks[track].sample_rate;
     st->codec->bits_per_coded_sample = fourxm->tracks[track].bits;
     st->codec->bit_rate              = st->codec->channels *
                                        st->codec->sample_rate *
                                        st->codec->bits_per_coded_sample;
     st->codec->block_align           = st->codec->channels *
                                        st->codec->bits_per_coded_sample;

     if (fourxm->tracks[track].adpcm){
         st->codec->codec_id = AV_CODEC_ID_ADPCM_4XM;
     } else if (st->codec->bits_per_coded_sample == 8) {
         st->codec->codec_id = AV_CODEC_ID_PCM_U8;
     } else
         st->codec->codec_id = AV_CODEC_ID_PCM_S16LE;

     return 0;
 }

 static int fourxm_read_header(AVFormatContext *s)
 {
     AVIOContext *pb = s->pb;
     unsigned int fourcc_tag;
     unsigned int size;
     int header_size;
     FourxmDemuxContext *fourxm = s->priv_data;
     unsigned char *header;
     int i, ret;

     fourxm->track_count = 0;
     fourxm->tracks      = NULL;
     fourxm->fps         = (AVRational){1,1};

     /* skip the first 3 32-bit numbers */
     avio_skip(pb, 12);

     /* check for LIST-HEAD */
     GET_LIST_HEADER();
     header_size = size - 4;
     if (fourcc_tag != HEAD_TAG || header_size < 0)
         return AVERROR_INVALIDDATA;

     /* allocate space for the header and load the whole thing */
     header = av_malloc(header_size);
     if (!header)
         return AVERROR(ENOMEM);
     if (avio_read(pb, header, header_size) != header_size) {
         av_free(header);
         return AVERROR(EIO);
     }

     /* take the lazy approach and search for any and all vtrk and strk chunks */
     for (i = 0; i < header_size - 8; i++) {
         fourcc_tag = AV_RL32(&header[i]);
         size       = AV_RL32(&header[i + 4]);
         if (size > header_size - i - 8 && (fourcc_tag == vtrk_TAG || fourcc_tag == strk_TAG)) {
             av_log(s, AV_LOG_ERROR, "chunk larger than array %d>%d\n", size, header_size - i - 8);
             return AVERROR_INVALIDDATA;
         }

         if (fourcc_tag == std__TAG) {
             if (header_size - i < 16) {
                 av_log(s, AV_LOG_ERROR, "std TAG truncated\n");
                 ret = AVERROR_INVALIDDATA;
                 goto fail;
             }
             fourxm->fps = av_d2q(av_int2float(AV_RL32(&header[i + 12])), 10000);
         } else if (fourcc_tag == vtrk_TAG) {
             if ((ret = parse_vtrk(s, fourxm, header + i, size,
                                   header_size - i)) < 0)
                 goto fail;

             i += 8 + size;
         } else if (fourcc_tag == strk_TAG) {
             if ((ret = parse_strk(s, fourxm, header + i, size,
                                   header_size - i)) < 0)
                 goto fail;

             i += 8 + size;
         }
     }

     /* skip over the LIST-MOVI chunk (which is where the stream should be */
     GET_LIST_HEADER();
     if (fourcc_tag != MOVI_TAG) {
         ret = AVERROR_INVALIDDATA;
         goto fail;
     }

     av_free(header);
     /* initialize context members */
     fourxm->video_pts = -1;  /* first frame will push to 0 */

     return 0;
 fail:
     av_freep(&fourxm->tracks);
     av_free(header);
     return ret;
 }

 static int fourxm_read_packet(AVFormatContext *s,
                               AVPacket *pkt)
 {
     FourxmDemuxContext *fourxm = s->priv_data;
     AVIOContext *pb            = s->pb;
     unsigned int fourcc_tag;
     unsigned int size;
     int ret = 0;
     unsigned int track_number;
     int packet_read = 0;
     unsigned char header[8];
     int audio_frame_count;

     while (!packet_read) {
         if ((ret = avio_read(s->pb, header, 8)) < 0)
             return ret;
         fourcc_tag = AV_RL32(&header[0]);
         size       = AV_RL32(&header[4]);
         if (avio_feof(pb))
             return AVERROR(EIO);
         switch (fourcc_tag) {
         case LIST_TAG:
             /* this is a good time to bump the video pts */
             fourxm->video_pts++;

             /* skip the LIST-* tag and move on to the next fourcc */
             avio_rl32(pb);
             break;

         case ifrm_TAG:
         case pfrm_TAG:
         case cfrm_TAG:
         case ifr2_TAG:
         case pfr2_TAG:
         case cfr2_TAG:
             /* allocate 8 more bytes than 'size' to account for fourcc
              * and size */
             if (size + 8 < size || av_new_packet(pkt, size + 8))
                 return AVERROR(EIO);
             pkt->stream_index = fourxm->video_stream_index;
             pkt->pts          = fourxm->video_pts;
             pkt->pos          = avio_tell(s->pb);
             memcpy(pkt->data, header, 8);
             ret = avio_read(s->pb, &pkt->data[8], size);

             if (ret < 0) {
                 av_packet_unref(pkt);
             } else {
                 packet_read = 1;
                 av_shrink_packet(pkt, ret + 8);
             }
             break;

         case snd__TAG:
             track_number = avio_rl32(pb);
             avio_skip(pb, 4);
             size -= 8;

             if (track_number < fourxm->track_count &&
                 fourxm->tracks[track_number].channels > 0) {
                 ret = av_get_packet(s->pb, pkt, size);
                 if (ret < 0)
                     return AVERROR(EIO);
                 pkt->stream_index =
                     fourxm->tracks[track_number].stream_index;
                 pkt->pts    = fourxm->tracks[track_number].audio_pts;
                 packet_read = 1;

                 /* pts accounting */
                 audio_frame_count = size;
                 if (fourxm->tracks[track_number].adpcm)
                     audio_frame_count -= 2 * (fourxm->tracks[track_number].channels);
                 audio_frame_count /= fourxm->tracks[track_number].channels;
                 if (fourxm->tracks[track_number].adpcm) {
                     audio_frame_count *= 2;
                 } else
                     audio_frame_count /=
                         (fourxm->tracks[track_number].bits / 8);
                 fourxm->tracks[track_number].audio_pts += audio_frame_count;
             } else {
                 avio_skip(pb, size);
             }
             break;

         default:
             avio_skip(pb, size);
             break;
         }
     }
     return ret;
 }

 static int fourxm_read_close(AVFormatContext *s)
 {
     FourxmDemuxContext *fourxm = s->priv_data;

     av_freep(&fourxm->tracks);

     return 0;
 }

 AVInputFormat ff_fourxm_demuxer = {
     .name           = "4xm",
     .long_name      = NULL_IF_CONFIG_SMALL("4X Technologies"),
     .priv_data_size = sizeof(FourxmDemuxContext),
     .read_probe     = fourxm_probe,
     .read_header    = fourxm_read_header,
     .read_packet    = fourxm_read_packet,
     .read_close     = fourxm_read_close,
 };
	/*
	* 4X Technologies .4xm File Demuxer (no muxer)
	* Copyright (c) 2003 The FFmpeg Project
	*
	* 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
	* 4X Technologies file demuxer
	* by Mike Melanson (melanson@pcisys.net)
	* for more information on the .4xm file format, visit:
	* http://www.pcisys.net/~melanson/codecs/
	*/

	#include "libavutil/intreadwrite.h"
	#include "libavutil/intfloat.h"
	#include "avformat.h"
	#include "internal.h"

	#define RIFF_TAG MKTAG('R', 'I', 'F', 'F')
	#define FOURXMV_TAG MKTAG('4', 'X', 'M', 'V')
	#define LIST_TAG MKTAG('L', 'I', 'S', 'T')
	#define HEAD_TAG MKTAG('H', 'E', 'A', 'D')
	#define TRK__TAG MKTAG('T', 'R', 'K', '_')
	#define MOVI_TAG MKTAG('M', 'O', 'V', 'I')
	#define VTRK_TAG MKTAG('V', 'T', 'R', 'K')
	#define STRK_TAG MKTAG('S', 'T', 'R', 'K')
	#define std__TAG MKTAG('s', 't', 'd', '_')
	#define name_TAG MKTAG('n', 'a', 'm', 'e')
	#define vtrk_TAG MKTAG('v', 't', 'r', 'k')
	#define strk_TAG MKTAG('s', 't', 'r', 'k')
	#define ifrm_TAG MKTAG('i', 'f', 'r', 'm')
	#define pfrm_TAG MKTAG('p', 'f', 'r', 'm')
	#define cfrm_TAG MKTAG('c', 'f', 'r', 'm')
	#define ifr2_TAG MKTAG('i', 'f', 'r', '2')
	#define pfr2_TAG MKTAG('p', 'f', 'r', '2')
	#define cfr2_TAG MKTAG('c', 'f', 'r', '2')
	#define snd__TAG MKTAG('s', 'n', 'd', '_')

	#define vtrk_SIZE 0x44
	#define strk_SIZE 0x28

	#define GET_LIST_HEADER() \
	fourcc_tag = avio_rl32(pb); \
	size = avio_rl32(pb); \
	if (fourcc_tag != LIST_TAG) \
	return AVERROR_INVALIDDATA; \
	fourcc_tag = avio_rl32(pb);

	typedef struct AudioTrack {
	int sample_rate;
	int bits;
	int channels;
	int stream_index;
	int adpcm;
	int64_t audio_pts;
	} AudioTrack;

	typedef struct FourxmDemuxContext {
	int video_stream_index;
	int track_count;
	AudioTrack *tracks;

	int64_t video_pts;
	AVRational fps;
	} FourxmDemuxContext;

	static int fourxm_probe(AVProbeData *p)
	{
	if ((AV_RL32(&p->buf[0]) != RIFF_TAG) \|\|
	(AV_RL32(&p->buf[8]) != FOURXMV_TAG))
	return 0;

	return AVPROBE_SCORE_MAX;
	}

	static int parse_vtrk(AVFormatContext *s,
	FourxmDemuxContext fourxm, uint8_t buf, int size,
	int left)
	{
	AVStream *st;
	/* check that there is enough data */
	if (size != vtrk_SIZE \|\| left < size + 8) {
	return AVERROR_INVALIDDATA;
	}

	/* allocate a new AVStream */
	st = avformat_new_stream(s, NULL);
	if (!st)
	return AVERROR(ENOMEM);

	avpriv_set_pts_info(st, 60, fourxm->fps.den, fourxm->fps.num);

	fourxm->video_stream_index = st->index;

	st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
	st->codec->codec_id = AV_CODEC_ID_4XM;

	st->codec->extradata = av_mallocz(4 + AV_INPUT_BUFFER_PADDING_SIZE);
	if (!st->codec->extradata)
	return AVERROR(ENOMEM);
	st->codec->extradata_size = 4;
	AV_WL32(st->codec->extradata, AV_RL32(buf + 16));
	st->codec->width = AV_RL32(buf + 36);
	st->codec->height = AV_RL32(buf + 40);

	return 0;
	}


	static int parse_strk(AVFormatContext *s,
	FourxmDemuxContext fourxm, uint8_t buf, int size,
	int left)
	{
	AVStream *st;
	int track;
	/* check that there is enough data */
	if (size != strk_SIZE \|\| left < size + 8)
	return AVERROR_INVALIDDATA;

	track = AV_RL32(buf + 8);
	if ((unsigned)track >= UINT_MAX / sizeof(AudioTrack) - 1) {
	av_log(s, AV_LOG_ERROR, "current_track too large\n");
	return AVERROR_INVALIDDATA;
	}

	if (track + 1 > fourxm->track_count) {
	if (av_reallocp_array(&fourxm->tracks, track + 1, sizeof(AudioTrack)))
	return AVERROR(ENOMEM);
	memset(&fourxm->tracks[fourxm->track_count], 0,
	sizeof(AudioTrack) * (track + 1 - fourxm->track_count));
	fourxm->track_count = track + 1;
	}
	fourxm->tracks[track].adpcm = AV_RL32(buf + 12);
	fourxm->tracks[track].channels = AV_RL32(buf + 36);
	fourxm->tracks[track].sample_rate = AV_RL32(buf + 40);
	fourxm->tracks[track].bits = AV_RL32(buf + 44);
	fourxm->tracks[track].audio_pts = 0;

	if (fourxm->tracks[track].channels <= 0 \|\|
	fourxm->tracks[track].sample_rate <= 0 \|\|
	fourxm->tracks[track].bits <= 0) {
	av_log(s, AV_LOG_ERROR, "audio header invalid\n");
	return AVERROR_INVALIDDATA;
	}
	if (!fourxm->tracks[track].adpcm && fourxm->tracks[track].bits<8) {
	av_log(s, AV_LOG_ERROR, "bits unspecified for non ADPCM\n");
	return AVERROR_INVALIDDATA;
	}

	/* allocate a new AVStream */
	st = avformat_new_stream(s, NULL);
	if (!st)
	return AVERROR(ENOMEM);

	st->id = track;
	avpriv_set_pts_info(st, 60, 1, fourxm->tracks[track].sample_rate);

	fourxm->tracks[track].stream_index = st->index;

	st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
	st->codec->codec_tag = 0;
	st->codec->channels = fourxm->tracks[track].channels;
	st->codec->sample_rate = fourxm->tracks[track].sample_rate;
	st->codec->bits_per_coded_sample = fourxm->tracks[track].bits;
	st->codec->bit_rate = st->codec->channels *
	st->codec->sample_rate *
	st->codec->bits_per_coded_sample;
	st->codec->block_align = st->codec->channels *
	st->codec->bits_per_coded_sample;

	if (fourxm->tracks[track].adpcm){
	st->codec->codec_id = AV_CODEC_ID_ADPCM_4XM;
	} else if (st->codec->bits_per_coded_sample == 8) {
	st->codec->codec_id = AV_CODEC_ID_PCM_U8;
	} else
	st->codec->codec_id = AV_CODEC_ID_PCM_S16LE;

	return 0;
	}

	static int fourxm_read_header(AVFormatContext *s)
	{
	AVIOContext *pb = s->pb;
	unsigned int fourcc_tag;
	unsigned int size;
	int header_size;
	FourxmDemuxContext *fourxm = s->priv_data;
	unsigned char *header;
	int i, ret;

	fourxm->track_count = 0;
	fourxm->tracks = NULL;
	fourxm->fps = (AVRational){1,1};

	/* skip the first 3 32-bit numbers */
	avio_skip(pb, 12);

	/* check for LIST-HEAD */
	GET_LIST_HEADER();
	header_size = size - 4;
	if (fourcc_tag != HEAD_TAG \|\| header_size < 0)
	return AVERROR_INVALIDDATA;

	/* allocate space for the header and load the whole thing */
	header = av_malloc(header_size);
	if (!header)
	return AVERROR(ENOMEM);
	if (avio_read(pb, header, header_size) != header_size) {
	av_free(header);
	return AVERROR(EIO);
	}

	/* take the lazy approach and search for any and all vtrk and strk chunks */
	for (i = 0; i < header_size - 8; i++) {
	fourcc_tag = AV_RL32(&header[i]);
	size = AV_RL32(&header[i + 4]);
	if (size > header_size - i - 8 && (fourcc_tag == vtrk_TAG \|\| fourcc_tag == strk_TAG)) {
	av_log(s, AV_LOG_ERROR, "chunk larger than array %d>%d\n", size, header_size - i - 8);
	return AVERROR_INVALIDDATA;
	}

	if (fourcc_tag == std__TAG) {
	if (header_size - i < 16) {
	av_log(s, AV_LOG_ERROR, "std TAG truncated\n");
	ret = AVERROR_INVALIDDATA;
	goto fail;
	}
	fourxm->fps = av_d2q(av_int2float(AV_RL32(&header[i + 12])), 10000);
	} else if (fourcc_tag == vtrk_TAG) {
	if ((ret = parse_vtrk(s, fourxm, header + i, size,
	header_size - i)) < 0)
	goto fail;

	i += 8 + size;
	} else if (fourcc_tag == strk_TAG) {
	if ((ret = parse_strk(s, fourxm, header + i, size,
	header_size - i)) < 0)
	goto fail;

	i += 8 + size;
	}
	}

	/* skip over the LIST-MOVI chunk (which is where the stream should be */
	GET_LIST_HEADER();
	if (fourcc_tag != MOVI_TAG) {
	ret = AVERROR_INVALIDDATA;
	goto fail;
	}

	av_free(header);
	/* initialize context members */
	fourxm->video_pts = -1; /* first frame will push to 0 */

	return 0;
	fail:
	av_freep(&fourxm->tracks);
	av_free(header);
	return ret;
	}

	static int fourxm_read_packet(AVFormatContext *s,
	AVPacket *pkt)
	{
	FourxmDemuxContext *fourxm = s->priv_data;
	AVIOContext *pb = s->pb;
	unsigned int fourcc_tag;
	unsigned int size;
	int ret = 0;
	unsigned int track_number;
	int packet_read = 0;
	unsigned char header[8];
	int audio_frame_count;

	while (!packet_read) {
	if ((ret = avio_read(s->pb, header, 8)) < 0)
	return ret;
	fourcc_tag = AV_RL32(&header[0]);
	size = AV_RL32(&header[4]);
	if (avio_feof(pb))
	return AVERROR(EIO);
	switch (fourcc_tag) {
	case LIST_TAG:
	/* this is a good time to bump the video pts */
	fourxm->video_pts++;

	/* skip the LIST-* tag and move on to the next fourcc */
	avio_rl32(pb);
	break;

	case ifrm_TAG:
	case pfrm_TAG:
	case cfrm_TAG:
	case ifr2_TAG:
	case pfr2_TAG:
	case cfr2_TAG:
	/* allocate 8 more bytes than 'size' to account for fourcc
	* and size */
	if (size + 8 < size \|\| av_new_packet(pkt, size + 8))
	return AVERROR(EIO);
	pkt->stream_index = fourxm->video_stream_index;
	pkt->pts = fourxm->video_pts;
	pkt->pos = avio_tell(s->pb);
	memcpy(pkt->data, header, 8);
	ret = avio_read(s->pb, &pkt->data[8], size);

	if (ret < 0) {
	av_packet_unref(pkt);
	} else {
	packet_read = 1;
	av_shrink_packet(pkt, ret + 8);
	}
	break;

	case snd__TAG:
	track_number = avio_rl32(pb);
	avio_skip(pb, 4);
	size -= 8;

	if (track_number < fourxm->track_count &&
	fourxm->tracks[track_number].channels > 0) {
	ret = av_get_packet(s->pb, pkt, size);
	if (ret < 0)
	return AVERROR(EIO);
	pkt->stream_index =
	fourxm->tracks[track_number].stream_index;
	pkt->pts = fourxm->tracks[track_number].audio_pts;
	packet_read = 1;

	/* pts accounting */
	audio_frame_count = size;
	if (fourxm->tracks[track_number].adpcm)
	audio_frame_count -= 2 * (fourxm->tracks[track_number].channels);
	audio_frame_count /= fourxm->tracks[track_number].channels;
	if (fourxm->tracks[track_number].adpcm) {
	audio_frame_count *= 2;
	} else
	audio_frame_count /=
	(fourxm->tracks[track_number].bits / 8);
	fourxm->tracks[track_number].audio_pts += audio_frame_count;
	} else {
	avio_skip(pb, size);
	}
	break;

	default:
	avio_skip(pb, size);
	break;
	}
	}
	return ret;
	}

	static int fourxm_read_close(AVFormatContext *s)
	{
	FourxmDemuxContext *fourxm = s->priv_data;

	av_freep(&fourxm->tracks);

	return 0;
	}

	AVInputFormat ff_fourxm_demuxer = {
	.name = "4xm",
	.long_name = NULL_IF_CONFIG_SMALL("4X Technologies"),
	.priv_data_size = sizeof(FourxmDemuxContext),
	.read_probe = fourxm_probe,
	.read_header = fourxm_read_header,
	.read_packet = fourxm_read_packet,
	.read_close = fourxm_read_close,
	};