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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.
102 lines
3.1 KiB
C
102 lines
3.1 KiB
C
/*
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* RIFF common functions and data
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* copyright (c) 2000 Fabrice Bellard
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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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/**
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* @file
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* internal header for RIFF based (de)muxers
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* do NOT include this in end user applications
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*/
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#ifndef AVFORMAT_RIFF_H
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#define AVFORMAT_RIFF_H
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#include "libavcodec/avcodec.h"
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#include "avio.h"
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#include "internal.h"
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#include "metadata.h"
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extern const AVMetadataConv ff_riff_info_conv[];
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int64_t ff_start_tag(AVIOContext *pb, const char *tag);
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void ff_end_tag(AVIOContext *pb, int64_t start);
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/**
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* Read BITMAPINFOHEADER structure and set AVStream codec width, height and
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* bits_per_encoded_sample fields. Does not read extradata.
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* @return codec tag
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*/
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int ff_get_bmp_header(AVIOContext *pb, AVStream *st);
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void ff_put_bmp_header(AVIOContext *pb, AVCodecParameters *par, const AVCodecTag *tags, int for_asf);
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int ff_put_wav_header(AVFormatContext *s, AVIOContext *pb, AVCodecParameters *par);
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enum AVCodecID ff_wav_codec_get_id(unsigned int tag, int bps);
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int ff_get_wav_header(AVFormatContext *s, AVIOContext *pb, AVCodecParameters *par, int size);
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extern const AVCodecTag ff_codec_bmp_tags[];
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extern const AVCodecTag ff_codec_wav_tags[];
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void ff_parse_specific_params(AVStream *st, int *au_rate, int *au_ssize, int *au_scale);
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int ff_read_riff_info(AVFormatContext *s, int64_t size);
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/**
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* Write all recognized RIFF tags from s->metadata
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*/
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void ff_riff_write_info(AVFormatContext *s);
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/**
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* Write a single RIFF info tag
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*/
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void ff_riff_write_info_tag(AVIOContext *pb, const char *tag, const char *str);
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typedef uint8_t ff_asf_guid[16];
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typedef struct AVCodecGuid {
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enum AVCodecID id;
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ff_asf_guid guid;
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} AVCodecGuid;
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extern const AVCodecGuid ff_codec_wav_guids[];
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#define FF_PRI_GUID \
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"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x"
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#define FF_ARG_GUID(g) \
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g[0], g[1], g[2], g[3], g[4], g[5], g[6], g[7], \
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g[8], g[9], g[10], g[11], g[12], g[13], g[14], g[15]
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#define FF_MEDIASUBTYPE_BASE_GUID \
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0x00, 0x00, 0x10, 0x00, 0x80, 0x00, 0x00, 0xAA, 0x00, 0x38, 0x9B, 0x71
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static av_always_inline int ff_guidcmp(const void *g1, const void *g2)
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{
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return memcmp(g1, g2, sizeof(ff_asf_guid));
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}
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static av_always_inline int ff_get_guid(AVIOContext *s, ff_asf_guid *g)
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{
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return avio_read(s, *g, sizeof(*g));
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}
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enum AVCodecID ff_codec_guid_get_id(const AVCodecGuid *guids, ff_asf_guid guid);
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#endif /* AVFORMAT_RIFF_H */
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