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![Anton Khirnov](/assets/img/avatar_default.png)
Currently, AVStream contains an embedded AVCodecContext instance, which is used by demuxers to export stream parameters to the caller and by muxers to receive stream parameters from the caller. It is also used internally as the codec context that is passed to parsers. In addition, it is also widely used by the callers as the decoding (when demuxer) or encoding (when muxing) context, though this has been officially discouraged since Libav 11. There are multiple important problems with this approach: - the fields in AVCodecContext are in general one of * stream parameters * codec options * codec state However, it's not clear which ones are which. It is consequently unclear which fields are a demuxer allowed to set or a muxer allowed to read. This leads to erratic behaviour depending on whether decoding or encoding is being performed or not (and whether it uses the AVStream embedded codec context). - various synchronization issues arising from the fact that the same context is used by several different APIs (muxers/demuxers, parsers, bitstream filters and encoders/decoders) simultaneously, with there being no clear rules for who can modify what and the different processes being typically delayed with respect to each other. - avformat_find_stream_info() making it necessary to support opening and closing a single codec context multiple times, thus complicating the semantics of freeing various allocated objects in the codec context. Those problems are resolved by replacing the AVStream embedded codec context with a newly added AVCodecParameters instance, which stores only the stream parameters exported by the demuxers or read by the muxers.
219 lines
6.3 KiB
C
219 lines
6.3 KiB
C
/*
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* RAW demuxers
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* Copyright (c) 2001 Fabrice Bellard
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* Copyright (c) 2005 Alex Beregszaszi
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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 "avformat.h"
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#include "internal.h"
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#include "avio_internal.h"
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#include "rawdec.h"
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#include "libavutil/opt.h"
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#include "libavutil/parseutils.h"
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#include "libavutil/pixdesc.h"
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#include "libavutil/intreadwrite.h"
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#define RAW_PACKET_SIZE 1024
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int ff_raw_read_partial_packet(AVFormatContext *s, AVPacket *pkt)
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{
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int ret, size;
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size = RAW_PACKET_SIZE;
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if (av_new_packet(pkt, size) < 0)
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return AVERROR(ENOMEM);
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pkt->pos= avio_tell(s->pb);
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pkt->stream_index = 0;
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ret = ffio_read_partial(s->pb, pkt->data, size);
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if (ret < 0) {
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av_packet_unref(pkt);
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return ret;
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} else if (ret < size) {
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/* initialize end of packet for partial reads to avoid reading
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* uninitialized data on allowed overreads */
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memset(pkt->data + ret, 0, AV_INPUT_BUFFER_PADDING_SIZE);
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}
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pkt->size = ret;
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return ret;
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}
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int ff_raw_audio_read_header(AVFormatContext *s)
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{
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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->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
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st->codecpar->codec_id = s->iformat->raw_codec_id;
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st->need_parsing = AVSTREAM_PARSE_FULL;
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st->start_time = 0;
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/* the parameters will be extracted from the compressed bitstream */
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return 0;
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}
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/* MPEG-1/H.263 input */
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int ff_raw_video_read_header(AVFormatContext *s)
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{
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AVStream *st;
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FFRawVideoDemuxerContext *s1 = s->priv_data;
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AVRational framerate;
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int ret = 0;
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st = avformat_new_stream(s, NULL);
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if (!st) {
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ret = AVERROR(ENOMEM);
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goto fail;
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}
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st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
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st->codecpar->codec_id = s->iformat->raw_codec_id;
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st->need_parsing = AVSTREAM_PARSE_FULL;
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if ((ret = av_parse_video_rate(&framerate, s1->framerate)) < 0) {
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av_log(s, AV_LOG_ERROR, "Could not parse framerate: %s.\n", s1->framerate);
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goto fail;
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}
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st->avg_frame_rate = framerate;
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avpriv_set_pts_info(st, 64, framerate.den, framerate.num);
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fail:
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return ret;
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}
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/* Note: Do not forget to add new entries to the Makefile as well. */
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#define OFFSET(x) offsetof(FFRawVideoDemuxerContext, x)
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#define DEC AV_OPT_FLAG_DECODING_PARAM
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const AVOption ff_rawvideo_options[] = {
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{ "framerate", "", OFFSET(framerate), AV_OPT_TYPE_STRING, {.str = "25"}, 0, 0, DEC},
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{ NULL },
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};
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#if CONFIG_LATM_DEMUXER
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#define LOAS_SYNC_WORD 0x2b7
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static int latm_read_probe(AVProbeData *p)
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{
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int max_frames = 0, first_frames = 0;
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int fsize, frames;
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uint8_t *buf0 = p->buf;
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uint8_t *buf2;
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uint8_t *buf;
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uint8_t *end = buf0 + p->buf_size - 3;
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buf = buf0;
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for (; buf < end; buf = buf2 + 1) {
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buf2 = buf;
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for (frames = 0; buf2 < end; frames++) {
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uint32_t header = AV_RB24(buf2);
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if ((header >> 13) != LOAS_SYNC_WORD) {
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if (buf != buf0) {
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// Found something that isn't a LOAS header, starting
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// from a position other than the start of the buffer.
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// Discard the count we've accumulated so far since it
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// probably was a false positive.
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frames = 0;
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}
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break;
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}
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fsize = (header & 0x1FFF) + 3;
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if (fsize < 7)
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break;
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buf2 += fsize;
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}
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max_frames = FFMAX(max_frames, frames);
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if (buf == buf0)
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first_frames = frames;
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}
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if (first_frames >= 3)
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return AVPROBE_SCORE_EXTENSION + 1;
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else if (max_frames > 100)
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return AVPROBE_SCORE_EXTENSION;
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else if (max_frames >= 3)
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return AVPROBE_SCORE_EXTENSION / 2;
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else if (max_frames > 1)
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return 1;
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else
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return 0;
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}
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AVInputFormat ff_latm_demuxer = {
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.name = "latm",
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.long_name = NULL_IF_CONFIG_SMALL("raw LOAS/LATM"),
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.read_probe = latm_read_probe,
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.read_header = ff_raw_audio_read_header,
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.read_packet = ff_raw_read_partial_packet,
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.flags = AVFMT_GENERIC_INDEX,
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.extensions = "latm",
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.raw_codec_id = AV_CODEC_ID_AAC_LATM,
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};
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#endif
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#if CONFIG_MJPEG_DEMUXER
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FF_DEF_RAWVIDEO_DEMUXER(mjpeg, "raw MJPEG video", NULL, "mjpg,mjpeg", AV_CODEC_ID_MJPEG)
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#endif
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#if CONFIG_MLP_DEMUXER
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AVInputFormat ff_mlp_demuxer = {
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.name = "mlp",
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.long_name = NULL_IF_CONFIG_SMALL("raw MLP"),
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.read_header = ff_raw_audio_read_header,
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.read_packet = ff_raw_read_partial_packet,
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.flags = AVFMT_GENERIC_INDEX,
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.extensions = "mlp",
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.raw_codec_id = AV_CODEC_ID_MLP,
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};
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#endif
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#if CONFIG_TRUEHD_DEMUXER
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AVInputFormat ff_truehd_demuxer = {
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.name = "truehd",
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.long_name = NULL_IF_CONFIG_SMALL("raw TrueHD"),
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.read_header = ff_raw_audio_read_header,
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.read_packet = ff_raw_read_partial_packet,
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.flags = AVFMT_GENERIC_INDEX,
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.extensions = "thd",
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.raw_codec_id = AV_CODEC_ID_TRUEHD,
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};
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#endif
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#if CONFIG_SHORTEN_DEMUXER
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AVInputFormat ff_shorten_demuxer = {
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.name = "shn",
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.long_name = NULL_IF_CONFIG_SMALL("raw Shorten"),
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.read_header = ff_raw_audio_read_header,
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.read_packet = ff_raw_read_partial_packet,
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.flags = AVFMT_NOBINSEARCH | AVFMT_NOGENSEARCH | AVFMT_NO_BYTE_SEEK,
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.extensions = "shn",
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.raw_codec_id = AV_CODEC_ID_SHORTEN,
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};
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#endif
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#if CONFIG_VC1_DEMUXER
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FF_DEF_RAWVIDEO_DEMUXER(vc1, "raw VC-1", NULL, "vc1", AV_CODEC_ID_VC1)
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#endif
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