9200514ad8
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.
382 lines
15 KiB
C
382 lines
15 KiB
C
/*
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* Animated GIF muxer
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* Copyright (c) 2000 Fabrice Bellard
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*
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* first version by Francois Revol <revol@free.fr>
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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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* Features and limitations:
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* - currently no compression is performed,
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* in fact the size of the data is 9/8 the size of the image in 8bpp
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* - uses only a global standard palette
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* - tested with IE 5.0, Opera for BeOS, NetPositive (BeOS), and Mozilla (BeOS).
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*
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* Reference documents:
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* http://www.goice.co.jp/member/mo/formats/gif.html
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* http://astronomy.swin.edu.au/pbourke/dataformats/gif/
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* http://www.dcs.ed.ac.uk/home/mxr/gfx/2d/GIF89a.txt
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*
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* this url claims to have an LZW algorithm not covered by Unisys patent:
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* http://www.msg.net/utility/whirlgif/gifencod.html
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* could help reduce the size of the files _a lot_...
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* some sites mentions an RLE type compression also.
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*/
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#include "avformat.h"
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#include "libavutil/log.h"
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#include "libavutil/opt.h"
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/* The GIF format uses reversed order for bitstreams... */
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/* at least they don't use PDP_ENDIAN :) */
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#define BITSTREAM_WRITER_LE
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#include "libavcodec/put_bits.h"
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/* bitstream minipacket size */
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#define GIF_CHUNKS 100
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/* slows down the decoding (and some browsers don't like it) */
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/* update on the 'some browsers don't like it issue from above:
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* this was probably due to missing 'Data Sub-block Terminator'
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* (byte 19) in the app_header */
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#define GIF_ADD_APP_HEADER // required to enable looping of animated gif
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typedef struct rgb_triplet {
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unsigned char r;
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unsigned char g;
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unsigned char b;
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} rgb_triplet;
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/* we use the standard 216 color palette */
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/* this script was used to create the palette:
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* for r in 00 33 66 99 cc ff; do
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* for g in 00 33 66 99 cc ff; do
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* echo -n " "
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* for b in 00 33 66 99 cc ff; do
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* echo -n "{ 0x$r, 0x$g, 0x$b }, "
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* done
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* echo ""
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* done
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* done
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*/
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static const rgb_triplet gif_clut[216] = {
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{ 0x00, 0x00, 0x00 }, { 0x00, 0x00, 0x33 }, { 0x00, 0x00, 0x66 }, { 0x00, 0x00, 0x99 }, { 0x00, 0x00, 0xcc }, { 0x00, 0x00, 0xff },
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{ 0x00, 0x33, 0x00 }, { 0x00, 0x33, 0x33 }, { 0x00, 0x33, 0x66 }, { 0x00, 0x33, 0x99 }, { 0x00, 0x33, 0xcc }, { 0x00, 0x33, 0xff },
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{ 0x00, 0x66, 0x00 }, { 0x00, 0x66, 0x33 }, { 0x00, 0x66, 0x66 }, { 0x00, 0x66, 0x99 }, { 0x00, 0x66, 0xcc }, { 0x00, 0x66, 0xff },
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{ 0x00, 0x99, 0x00 }, { 0x00, 0x99, 0x33 }, { 0x00, 0x99, 0x66 }, { 0x00, 0x99, 0x99 }, { 0x00, 0x99, 0xcc }, { 0x00, 0x99, 0xff },
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{ 0x00, 0xcc, 0x00 }, { 0x00, 0xcc, 0x33 }, { 0x00, 0xcc, 0x66 }, { 0x00, 0xcc, 0x99 }, { 0x00, 0xcc, 0xcc }, { 0x00, 0xcc, 0xff },
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{ 0x00, 0xff, 0x00 }, { 0x00, 0xff, 0x33 }, { 0x00, 0xff, 0x66 }, { 0x00, 0xff, 0x99 }, { 0x00, 0xff, 0xcc }, { 0x00, 0xff, 0xff },
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{ 0x33, 0x00, 0x00 }, { 0x33, 0x00, 0x33 }, { 0x33, 0x00, 0x66 }, { 0x33, 0x00, 0x99 }, { 0x33, 0x00, 0xcc }, { 0x33, 0x00, 0xff },
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{ 0x33, 0x33, 0x00 }, { 0x33, 0x33, 0x33 }, { 0x33, 0x33, 0x66 }, { 0x33, 0x33, 0x99 }, { 0x33, 0x33, 0xcc }, { 0x33, 0x33, 0xff },
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{ 0x33, 0x66, 0x00 }, { 0x33, 0x66, 0x33 }, { 0x33, 0x66, 0x66 }, { 0x33, 0x66, 0x99 }, { 0x33, 0x66, 0xcc }, { 0x33, 0x66, 0xff },
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{ 0x33, 0x99, 0x00 }, { 0x33, 0x99, 0x33 }, { 0x33, 0x99, 0x66 }, { 0x33, 0x99, 0x99 }, { 0x33, 0x99, 0xcc }, { 0x33, 0x99, 0xff },
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{ 0x33, 0xcc, 0x00 }, { 0x33, 0xcc, 0x33 }, { 0x33, 0xcc, 0x66 }, { 0x33, 0xcc, 0x99 }, { 0x33, 0xcc, 0xcc }, { 0x33, 0xcc, 0xff },
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{ 0x33, 0xff, 0x00 }, { 0x33, 0xff, 0x33 }, { 0x33, 0xff, 0x66 }, { 0x33, 0xff, 0x99 }, { 0x33, 0xff, 0xcc }, { 0x33, 0xff, 0xff },
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{ 0x66, 0x00, 0x00 }, { 0x66, 0x00, 0x33 }, { 0x66, 0x00, 0x66 }, { 0x66, 0x00, 0x99 }, { 0x66, 0x00, 0xcc }, { 0x66, 0x00, 0xff },
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{ 0x66, 0x33, 0x00 }, { 0x66, 0x33, 0x33 }, { 0x66, 0x33, 0x66 }, { 0x66, 0x33, 0x99 }, { 0x66, 0x33, 0xcc }, { 0x66, 0x33, 0xff },
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{ 0x66, 0x66, 0x00 }, { 0x66, 0x66, 0x33 }, { 0x66, 0x66, 0x66 }, { 0x66, 0x66, 0x99 }, { 0x66, 0x66, 0xcc }, { 0x66, 0x66, 0xff },
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{ 0x66, 0x99, 0x00 }, { 0x66, 0x99, 0x33 }, { 0x66, 0x99, 0x66 }, { 0x66, 0x99, 0x99 }, { 0x66, 0x99, 0xcc }, { 0x66, 0x99, 0xff },
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{ 0x66, 0xcc, 0x00 }, { 0x66, 0xcc, 0x33 }, { 0x66, 0xcc, 0x66 }, { 0x66, 0xcc, 0x99 }, { 0x66, 0xcc, 0xcc }, { 0x66, 0xcc, 0xff },
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{ 0x66, 0xff, 0x00 }, { 0x66, 0xff, 0x33 }, { 0x66, 0xff, 0x66 }, { 0x66, 0xff, 0x99 }, { 0x66, 0xff, 0xcc }, { 0x66, 0xff, 0xff },
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{ 0x99, 0x00, 0x00 }, { 0x99, 0x00, 0x33 }, { 0x99, 0x00, 0x66 }, { 0x99, 0x00, 0x99 }, { 0x99, 0x00, 0xcc }, { 0x99, 0x00, 0xff },
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{ 0x99, 0x33, 0x00 }, { 0x99, 0x33, 0x33 }, { 0x99, 0x33, 0x66 }, { 0x99, 0x33, 0x99 }, { 0x99, 0x33, 0xcc }, { 0x99, 0x33, 0xff },
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{ 0x99, 0x66, 0x00 }, { 0x99, 0x66, 0x33 }, { 0x99, 0x66, 0x66 }, { 0x99, 0x66, 0x99 }, { 0x99, 0x66, 0xcc }, { 0x99, 0x66, 0xff },
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{ 0x99, 0x99, 0x00 }, { 0x99, 0x99, 0x33 }, { 0x99, 0x99, 0x66 }, { 0x99, 0x99, 0x99 }, { 0x99, 0x99, 0xcc }, { 0x99, 0x99, 0xff },
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{ 0x99, 0xcc, 0x00 }, { 0x99, 0xcc, 0x33 }, { 0x99, 0xcc, 0x66 }, { 0x99, 0xcc, 0x99 }, { 0x99, 0xcc, 0xcc }, { 0x99, 0xcc, 0xff },
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{ 0x99, 0xff, 0x00 }, { 0x99, 0xff, 0x33 }, { 0x99, 0xff, 0x66 }, { 0x99, 0xff, 0x99 }, { 0x99, 0xff, 0xcc }, { 0x99, 0xff, 0xff },
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{ 0xcc, 0x00, 0x00 }, { 0xcc, 0x00, 0x33 }, { 0xcc, 0x00, 0x66 }, { 0xcc, 0x00, 0x99 }, { 0xcc, 0x00, 0xcc }, { 0xcc, 0x00, 0xff },
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{ 0xcc, 0x33, 0x00 }, { 0xcc, 0x33, 0x33 }, { 0xcc, 0x33, 0x66 }, { 0xcc, 0x33, 0x99 }, { 0xcc, 0x33, 0xcc }, { 0xcc, 0x33, 0xff },
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{ 0xcc, 0x66, 0x00 }, { 0xcc, 0x66, 0x33 }, { 0xcc, 0x66, 0x66 }, { 0xcc, 0x66, 0x99 }, { 0xcc, 0x66, 0xcc }, { 0xcc, 0x66, 0xff },
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{ 0xcc, 0x99, 0x00 }, { 0xcc, 0x99, 0x33 }, { 0xcc, 0x99, 0x66 }, { 0xcc, 0x99, 0x99 }, { 0xcc, 0x99, 0xcc }, { 0xcc, 0x99, 0xff },
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{ 0xcc, 0xcc, 0x00 }, { 0xcc, 0xcc, 0x33 }, { 0xcc, 0xcc, 0x66 }, { 0xcc, 0xcc, 0x99 }, { 0xcc, 0xcc, 0xcc }, { 0xcc, 0xcc, 0xff },
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{ 0xcc, 0xff, 0x00 }, { 0xcc, 0xff, 0x33 }, { 0xcc, 0xff, 0x66 }, { 0xcc, 0xff, 0x99 }, { 0xcc, 0xff, 0xcc }, { 0xcc, 0xff, 0xff },
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{ 0xff, 0x00, 0x00 }, { 0xff, 0x00, 0x33 }, { 0xff, 0x00, 0x66 }, { 0xff, 0x00, 0x99 }, { 0xff, 0x00, 0xcc }, { 0xff, 0x00, 0xff },
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{ 0xff, 0x33, 0x00 }, { 0xff, 0x33, 0x33 }, { 0xff, 0x33, 0x66 }, { 0xff, 0x33, 0x99 }, { 0xff, 0x33, 0xcc }, { 0xff, 0x33, 0xff },
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{ 0xff, 0x66, 0x00 }, { 0xff, 0x66, 0x33 }, { 0xff, 0x66, 0x66 }, { 0xff, 0x66, 0x99 }, { 0xff, 0x66, 0xcc }, { 0xff, 0x66, 0xff },
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{ 0xff, 0x99, 0x00 }, { 0xff, 0x99, 0x33 }, { 0xff, 0x99, 0x66 }, { 0xff, 0x99, 0x99 }, { 0xff, 0x99, 0xcc }, { 0xff, 0x99, 0xff },
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{ 0xff, 0xcc, 0x00 }, { 0xff, 0xcc, 0x33 }, { 0xff, 0xcc, 0x66 }, { 0xff, 0xcc, 0x99 }, { 0xff, 0xcc, 0xcc }, { 0xff, 0xcc, 0xff },
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{ 0xff, 0xff, 0x00 }, { 0xff, 0xff, 0x33 }, { 0xff, 0xff, 0x66 }, { 0xff, 0xff, 0x99 }, { 0xff, 0xff, 0xcc }, { 0xff, 0xff, 0xff },
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};
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/* GIF header */
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static int gif_image_write_header(AVIOContext *pb, int width, int height,
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int loop_count, uint32_t *palette)
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{
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int i;
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unsigned int v;
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avio_write(pb, "GIF", 3);
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avio_write(pb, "89a", 3);
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avio_wl16(pb, width);
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avio_wl16(pb, height);
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avio_w8(pb, 0xf7); /* flags: global clut, 256 entries */
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avio_w8(pb, 0x1f); /* background color index */
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avio_w8(pb, 0); /* aspect ratio */
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/* the global palette */
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if (!palette) {
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avio_write(pb, (const unsigned char *)gif_clut, 216 * 3);
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for (i = 0; i < ((256 - 216) * 3); i++)
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avio_w8(pb, 0);
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} else {
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for (i = 0; i < 256; i++) {
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v = palette[i];
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avio_w8(pb, (v >> 16) & 0xff);
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avio_w8(pb, (v >> 8) & 0xff);
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avio_w8(pb, (v) & 0xff);
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}
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}
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/* update: this is the 'NETSCAPE EXTENSION' that allows for looped animated
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* GIF, see http://members.aol.com/royalef/gifabout.htm#net-extension
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*
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* byte 1 : 33 (hex 0x21) GIF Extension code
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* byte 2 : 255 (hex 0xFF) Application Extension Label
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* byte 3 : 11 (hex (0x0B) Length of Application Block
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* (eleven bytes of data to follow)
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* bytes 4 to 11 : "NETSCAPE"
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* bytes 12 to 14 : "2.0"
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* byte 15 : 3 (hex 0x03) Length of Data Sub-Block
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* (three bytes of data to follow)
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* byte 16 : 1 (hex 0x01)
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* bytes 17 to 18 : 0 to 65535, an unsigned integer in
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* lo-hi byte format. This indicate the
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* number of iterations the loop should
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* be executed.
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* bytes 19 : 0 (hex 0x00) a Data Sub-block Terminator
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*/
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/* application extension header */
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#ifdef GIF_ADD_APP_HEADER
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if (loop_count >= 0 && loop_count <= 65535) {
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avio_w8(pb, 0x21);
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avio_w8(pb, 0xff);
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avio_w8(pb, 0x0b);
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// bytes 4 to 14
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avio_write(pb, "NETSCAPE2.0", sizeof("NETSCAPE2.0") - 1);
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avio_w8(pb, 0x03); // byte 15
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avio_w8(pb, 0x01); // byte 16
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avio_wl16(pb, (uint16_t)loop_count);
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avio_w8(pb, 0x00); // byte 19
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}
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#endif
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return 0;
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}
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/* this is maybe slow, but allows for extensions */
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static inline unsigned char gif_clut_index(uint8_t r, uint8_t g, uint8_t b)
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{
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return (((r) / 47) % 6) * 6 * 6 + (((g) / 47) % 6) * 6 + (((b) / 47) % 6);
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}
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static int gif_image_write_image(AVIOContext *pb,
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int x1, int y1, int width, int height,
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const uint8_t *buf, int linesize, int pix_fmt)
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{
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PutBitContext p;
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uint8_t buffer[200]; /* 100 * 9 / 8 = 113 */
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int i, left, w, v;
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const uint8_t *ptr;
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/* image block */
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avio_w8(pb, 0x2c);
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avio_wl16(pb, x1);
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avio_wl16(pb, y1);
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avio_wl16(pb, width);
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avio_wl16(pb, height);
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avio_w8(pb, 0x00); /* flags */
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/* no local clut */
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avio_w8(pb, 0x08);
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left = width * height;
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init_put_bits(&p, buffer, 130);
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/*
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* the thing here is the bitstream is written as little packets, with a size
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* byte before but it's still the same bitstream between packets (no flush !)
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*/
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ptr = buf;
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w = width;
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while (left > 0) {
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put_bits(&p, 9, 0x0100); /* clear code */
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for (i = (left < GIF_CHUNKS) ? left : GIF_CHUNKS; i; i--) {
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if (pix_fmt == AV_PIX_FMT_RGB24) {
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v = gif_clut_index(ptr[0], ptr[1], ptr[2]);
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ptr += 3;
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} else {
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v = *ptr++;
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}
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put_bits(&p, 9, v);
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if (--w == 0) {
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w = width;
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buf += linesize;
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ptr = buf;
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}
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}
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if (left <= GIF_CHUNKS) {
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put_bits(&p, 9, 0x101); /* end of stream */
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flush_put_bits(&p);
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}
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if (put_bits_ptr(&p) - p.buf > 0) {
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avio_w8(pb, put_bits_ptr(&p) - p.buf); /* byte count of the packet */
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avio_write(pb, p.buf, put_bits_ptr(&p) - p.buf); /* the actual buffer */
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p.buf_ptr = p.buf; /* dequeue the bytes off the bitstream */
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}
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left -= GIF_CHUNKS;
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}
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avio_w8(pb, 0x00); /* end of image block */
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return 0;
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}
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typedef struct GIFContext {
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AVClass *class; /** Class for private options. */
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int64_t time, file_time;
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uint8_t buffer[100]; /* data chunks */
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int loop;
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} GIFContext;
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static int gif_write_header(AVFormatContext *s)
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{
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GIFContext *gif = s->priv_data;
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AVIOContext *pb = s->pb;
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AVCodecParameters *par, *video_par;
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int i, width, height /*, rate*/;
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/* XXX: do we reject audio streams or just ignore them ?
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* if (s->nb_streams > 1)
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* return -1;
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*/
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gif->time = 0;
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gif->file_time = 0;
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video_par = NULL;
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for (i = 0; i < s->nb_streams; i++) {
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par = s->streams[i]->codecpar;
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if (par->codec_type != AVMEDIA_TYPE_AUDIO)
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video_par = par;
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}
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if (!video_par) {
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av_free(gif);
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return -1;
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} else {
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width = video_par->width;
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height = video_par->height;
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// rate = video_enc->time_base.den;
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}
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if (video_par->format != AV_PIX_FMT_RGB24) {
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av_log(s, AV_LOG_ERROR,
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"ERROR: gif only handles the rgb24 pixel format. Use -pix_fmt rgb24.\n");
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return AVERROR(EIO);
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}
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gif_image_write_header(pb, width, height, gif->loop, NULL);
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avio_flush(s->pb);
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return 0;
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}
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static int gif_write_video(AVFormatContext *s, AVStream *st,
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const uint8_t *buf, int size)
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{
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AVCodecParameters *par = st->codecpar;
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AVIOContext *pb = s->pb;
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int jiffies;
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/* graphic control extension block */
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avio_w8(pb, 0x21);
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avio_w8(pb, 0xf9);
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avio_w8(pb, 0x04); /* block size */
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avio_w8(pb, 0x04); /* flags */
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/* 1 jiffy is 1/70 s */
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/* the delay_time field indicates the number of jiffies - 1 */
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/* XXX: should use delay, in order to be more accurate */
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/* instead of using the same rounded value each time */
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/* XXX: don't even remember if I really use it for now */
|
|
jiffies = (70 * st->time_base.num / st->time_base.den) - 1;
|
|
|
|
avio_wl16(pb, jiffies);
|
|
|
|
avio_w8(pb, 0x1f); /* transparent color index */
|
|
avio_w8(pb, 0x00);
|
|
|
|
gif_image_write_image(pb, 0, 0, par->width, par->height,
|
|
buf, par->width * 3, AV_PIX_FMT_RGB24);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int gif_write_packet(AVFormatContext *s, AVPacket *pkt)
|
|
{
|
|
AVCodecParameters *par = s->streams[pkt->stream_index]->codecpar;
|
|
if (par->codec_type == AVMEDIA_TYPE_AUDIO)
|
|
return 0; /* just ignore audio */
|
|
else
|
|
return gif_write_video(s, s->streams[pkt->stream_index], pkt->data, pkt->size);
|
|
}
|
|
|
|
static int gif_write_trailer(AVFormatContext *s)
|
|
{
|
|
AVIOContext *pb = s->pb;
|
|
|
|
avio_w8(pb, 0x3b);
|
|
|
|
return 0;
|
|
}
|
|
|
|
#define OFFSET(x) offsetof(GIFContext, x)
|
|
#define ENC AV_OPT_FLAG_ENCODING_PARAM
|
|
static const AVOption options[] = {
|
|
{ "loop", "Number of times to loop the output.", OFFSET(loop),
|
|
AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 65535, ENC },
|
|
{ NULL },
|
|
};
|
|
|
|
static const AVClass gif_muxer_class = {
|
|
.class_name = "GIF muxer",
|
|
.item_name = av_default_item_name,
|
|
.version = LIBAVUTIL_VERSION_INT,
|
|
.option = options,
|
|
};
|
|
|
|
AVOutputFormat ff_gif_muxer = {
|
|
.name = "gif",
|
|
.long_name = NULL_IF_CONFIG_SMALL("GIF Animation"),
|
|
.mime_type = "image/gif",
|
|
.extensions = "gif",
|
|
.priv_data_size = sizeof(GIFContext),
|
|
.audio_codec = AV_CODEC_ID_NONE,
|
|
.video_codec = AV_CODEC_ID_RAWVIDEO,
|
|
.write_header = gif_write_header,
|
|
.write_packet = gif_write_packet,
|
|
.write_trailer = gif_write_trailer,
|
|
.priv_class = &gif_muxer_class,
|
|
};
|