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libavformat
mtv.c
Go to the documentation of this file.
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/*
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* mtv demuxer
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* Copyright (c) 2006 Reynaldo H. Verdejo Pinochet
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*
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* This file is part of Libav.
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*
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* Libav is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "
libavutil/bswap.h
"
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#include "
libavutil/intreadwrite.h
"
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#include "
avformat.h
"
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#include "
internal.h
"
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#define MTV_ASUBCHUNK_DATA_SIZE 500
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#define MTV_HEADER_SIZE 512
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#define MTV_AUDIO_PADDING_SIZE 12
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#define AUDIO_SAMPLING_RATE 44100
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typedef
struct
MTVDemuxContext
{
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unsigned
int
file_size
;
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unsigned
int
segments
;
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unsigned
int
audio_identifier
;
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unsigned
int
audio_br
;
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unsigned
int
img_colorfmt
;
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unsigned
int
img_bpp
;
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unsigned
int
img_width
;
//
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unsigned
int
img_height
;
//
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unsigned
int
img_segment_size
;
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unsigned
int
video_fps
;
//
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unsigned
int
full_segment_size
;
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}
MTVDemuxContext
;
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static
int
mtv_probe
(
AVProbeData
*p)
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{
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/* Magic is 'AMV' */
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if
(*p->
buf
!=
'A'
|| *(p->
buf
+ 1) !=
'M'
|| *(p->
buf
+ 2) !=
'V'
)
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return
0;
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/* Check for nonzero in bpp and (width|height) header fields */
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if
(!(p->
buf
[51] &&
AV_RL16
(&p->
buf
[52]) |
AV_RL16
(&p->
buf
[54])))
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return
0;
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/* If width or height are 0 then imagesize header field should not */
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if
(!
AV_RL16
(&p->
buf
[52]) || !
AV_RL16
(&p->
buf
[54]))
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{
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if
(!!
AV_RL16
(&p->
buf
[56]))
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return
AVPROBE_SCORE_EXTENSION
;
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else
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return
0;
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}
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if
(p->
buf
[51] != 16)
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return
AVPROBE_SCORE_EXTENSION
/ 2;
// But we are going to assume 16bpp anyway ..
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return
AVPROBE_SCORE_MAX
;
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}
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static
int
mtv_read_header
(
AVFormatContext
*s)
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{
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MTVDemuxContext
*mtv = s->
priv_data
;
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AVIOContext
*pb = s->
pb
;
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AVStream
*st;
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unsigned
int
audio_subsegments;
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avio_skip
(pb, 3);
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mtv->
file_size
=
avio_rl32
(pb);
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mtv->
segments
=
avio_rl32
(pb);
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avio_skip
(pb, 32);
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mtv->
audio_identifier
=
avio_rl24
(pb);
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mtv->
audio_br
=
avio_rl16
(pb);
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mtv->
img_colorfmt
=
avio_rl24
(pb);
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mtv->
img_bpp
=
avio_r8
(pb);
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mtv->
img_width
=
avio_rl16
(pb);
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mtv->
img_height
=
avio_rl16
(pb);
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mtv->
img_segment_size
=
avio_rl16
(pb);
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/* Calculate width and height if missing from header */
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if
(!mtv->
img_width
)
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mtv->
img_width
=mtv->
img_segment_size
/ (mtv->
img_bpp
>>3)
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/ mtv->
img_height
;
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if
(!mtv->
img_height
)
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mtv->
img_height
=mtv->
img_segment_size
/ (mtv->
img_bpp
>>3)
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/ mtv->
img_width
;
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avio_skip
(pb, 4);
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audio_subsegments =
avio_rl16
(pb);
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if
(audio_subsegments == 0) {
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avpriv_request_sample
(s,
"MTV files without audio"
);
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return
AVERROR_PATCHWELCOME
;
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}
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mtv->
full_segment_size
=
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audio_subsegments * (
MTV_AUDIO_PADDING_SIZE
+
MTV_ASUBCHUNK_DATA_SIZE
) +
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mtv->
img_segment_size
;
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mtv->
video_fps
= (mtv->
audio_br
/ 4) / audio_subsegments;
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// FIXME Add sanity check here
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// all systems go! init decoders
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// video - raw rgb565
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st =
avformat_new_stream
(s,
NULL
);
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if
(!st)
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return
AVERROR
(ENOMEM);
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avpriv_set_pts_info
(st, 64, 1, mtv->
video_fps
);
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st->
codec
->
codec_type
=
AVMEDIA_TYPE_VIDEO
;
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st->
codec
->
codec_id
=
AV_CODEC_ID_RAWVIDEO
;
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st->
codec
->
pix_fmt
=
AV_PIX_FMT_RGB565BE
;
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st->
codec
->
width
= mtv->
img_width
;
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st->
codec
->
height
= mtv->
img_height
;
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st->
codec
->
sample_rate
= mtv->
video_fps
;
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st->
codec
->
extradata
=
av_strdup
(
"BottomUp"
);
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st->
codec
->
extradata_size
= 9;
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// audio - mp3
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st =
avformat_new_stream
(s,
NULL
);
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if
(!st)
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return
AVERROR
(ENOMEM);
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avpriv_set_pts_info
(st, 64, 1,
AUDIO_SAMPLING_RATE
);
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st->
codec
->
codec_type
=
AVMEDIA_TYPE_AUDIO
;
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st->
codec
->
codec_id
=
AV_CODEC_ID_MP3
;
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st->
codec
->
bit_rate
= mtv->
audio_br
;
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st->
need_parsing
=
AVSTREAM_PARSE_FULL
;
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// Jump over header
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if
(
avio_seek
(pb,
MTV_HEADER_SIZE
, SEEK_SET) !=
MTV_HEADER_SIZE
)
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return
AVERROR
(EIO);
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return
0;
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}
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static
int
mtv_read_packet
(
AVFormatContext
*s,
AVPacket
*pkt)
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{
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MTVDemuxContext
*mtv = s->
priv_data
;
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AVIOContext
*pb = s->
pb
;
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int
ret;
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if
((
avio_tell
(pb) - s->
data_offset
+ mtv->
img_segment_size
) % mtv->
full_segment_size
)
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{
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avio_skip
(pb,
MTV_AUDIO_PADDING_SIZE
);
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ret =
av_get_packet
(pb, pkt,
MTV_ASUBCHUNK_DATA_SIZE
);
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if
(ret < 0)
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return
ret;
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pkt->
pos
-=
MTV_AUDIO_PADDING_SIZE
;
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pkt->
stream_index
= 1;
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}
else
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{
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ret =
av_get_packet
(pb, pkt, mtv->
img_segment_size
);
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if
(ret < 0)
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return
ret;
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pkt->
stream_index
= 0;
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}
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return
ret;
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}
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AVInputFormat
ff_mtv_demuxer
= {
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.
name
=
"mtv"
,
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.long_name =
NULL_IF_CONFIG_SMALL
(
"MTV"
),
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.priv_data_size =
sizeof
(
MTVDemuxContext
),
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.
read_probe
=
mtv_probe
,
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.
read_header
=
mtv_read_header
,
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.
read_packet
=
mtv_read_packet
,
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};
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