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libavformat
gsmdec.c
Go to the documentation of this file.
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/*
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* RAW GSM demuxer
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* Copyright (c) 2011 Justin Ruggles
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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/mathematics.h
"
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#include "
libavutil/opt.h
"
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#include "
avformat.h
"
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#include "
internal.h
"
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#define GSM_BLOCK_SIZE 33
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#define GSM_BLOCK_SAMPLES 160
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#define GSM_SAMPLE_RATE 8000
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typedef
struct
{
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AVClass
*
class
;
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int
sample_rate
;
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}
GSMDemuxerContext
;
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static
int
gsm_read_packet
(
AVFormatContext
*s,
AVPacket
*pkt)
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{
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int
ret,
size
;
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size =
GSM_BLOCK_SIZE
;
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pkt->
pos
=
avio_tell
(s->
pb
);
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pkt->
stream_index
= 0;
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ret =
av_get_packet
(s->
pb
, pkt, size);
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if
(ret <
GSM_BLOCK_SIZE
) {
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av_free_packet
(pkt);
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return
ret < 0 ? ret :
AVERROR
(EIO);
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}
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pkt->
size
= ret;
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pkt->
duration
= 1;
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pkt->
pts
= pkt->
pos
/
GSM_BLOCK_SIZE
;
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return
0;
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}
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static
int
gsm_read_header
(
AVFormatContext
*s,
AVFormatParameters
*ap)
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{
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GSMDemuxerContext
*c = s->
priv_data
;
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AVStream
*st =
avformat_new_stream
(s,
NULL
);
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if
(!st)
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return
AVERROR
(ENOMEM);
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st->
codec
->
codec_type
=
AVMEDIA_TYPE_AUDIO
;
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st->
codec
->
codec_id
= s->
iformat
->
value
;
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st->
codec
->
channels
= 1;
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st->
codec
->
sample_rate
= c->
sample_rate
;
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st->
codec
->
bit_rate
=
GSM_BLOCK_SIZE
* 8 * c->
sample_rate
/
GSM_BLOCK_SAMPLES
;
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avpriv_set_pts_info
(st, 64,
GSM_BLOCK_SAMPLES
,
GSM_SAMPLE_RATE
);
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return
0;
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}
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static
const
AVOption
options
[] = {
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{
"sample_rate"
,
""
, offsetof(
GSMDemuxerContext
, sample_rate),
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AV_OPT_TYPE_INT
, {.dbl =
GSM_SAMPLE_RATE
}, 1, INT_MAX /
GSM_BLOCK_SIZE
,
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AV_OPT_FLAG_DECODING_PARAM
},
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{
NULL
},
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};
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static
const
AVClass
class
= {
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.
class_name
=
"gsm demuxer"
,
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.item_name =
av_default_item_name
,
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.option =
options
,
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.version =
LIBAVUTIL_VERSION_INT
,
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};
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AVInputFormat
ff_gsm_demuxer
= {
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.
name
=
"gsm"
,
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.long_name =
NULL_IF_CONFIG_SMALL
(
"raw GSM"
),
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.priv_data_size =
sizeof
(
GSMDemuxerContext
),
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.
read_header
=
gsm_read_header
,
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.
read_packet
=
gsm_read_packet
,
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.
flags
=
AVFMT_GENERIC_INDEX
,
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.extensions =
"gsm"
,
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.value =
CODEC_ID_GSM
,
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.priv_class = &
class
,
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};