bc7df3bc64
APNG works with a single reference frame and an output frame. According to the spec, decoding APNG works by decoding the current IDAT/fdAT chunks (which decodes to a rectangular subregion of the whole image region), followed by either overwriting the region of the output frame with the newly decoded data or by blending the newly decoded data with the data from the reference frame onto the current subregion of the output frame. The remainder of the output frame is just copied from the reference frame. Then the reference frame might be left untouched (APNG_DISPOSE_OP_PREVIOUS), it might be replaced by the output frame (APNG_DISPOSE_OP_NONE) or the rectangular subregion corresponding to the just decoded frame has to be reset to black (APNG_DISPOSE_OP_BACKGROUND). The latter case is not handled correctly by our decoder: It only performs resetting the rectangle in the reference frame when decoding the next frame; and since commit b593abda6c642cb0c3959752dd235c2faf66837f it does not reset the reference frame permanently, but only temporarily (i.e. it only affects decoding the frame after the frame with APNG_DISPOSE_OP_BACKGROUND). This is a problem if the frame after the APNG_DISPOSE_OP_BACKGROUND frame uses APNG_DISPOSE_OP_PREVIOUS, because then the frame after the APNG_DISPOSE_OP_PREVIOUS frame has an incorrect reference frame. (If it is not followed by an APNG_DISPOSE_OP_PREVIOUS frame, the decoder only keeps a reference to the output frame, which is ok.) This commit fixes this by being much closer to the spec than the earlier code: Resetting the background is no longer postponed until the next frame; instead it is applied to the reference frame. Fixes ticket #9602. (For multithreaded decoding it was actually already broken since commit 5663301560d77486c7f7c03c1aa5f542fab23c24.) Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
FFmpeg README
FFmpeg is a collection of libraries and tools to process multimedia content such as audio, video, subtitles and related metadata.
Libraries
libavcodecprovides implementation of a wider range of codecs.libavformatimplements streaming protocols, container formats and basic I/O access.libavutilincludes hashers, decompressors and miscellaneous utility functions.libavfilterprovides means to alter decoded audio and video through a directed graph of connected filters.libavdeviceprovides an abstraction to access capture and playback devices.libswresampleimplements audio mixing and resampling routines.libswscaleimplements color conversion and scaling routines.
Tools
- ffmpeg is a command line toolbox to manipulate, convert and stream multimedia content.
- ffplay is a minimalistic multimedia player.
- ffprobe is a simple analysis tool to inspect multimedia content.
- Additional small tools such as
aviocat,ismindexandqt-faststart.
Documentation
The offline documentation is available in the doc/ directory.
The online documentation is available in the main website and in the wiki.
Examples
Coding examples are available in the doc/examples directory.
License
FFmpeg codebase is mainly LGPL-licensed with optional components licensed under GPL. Please refer to the LICENSE file for detailed information.
Contributing
Patches should be submitted to the ffmpeg-devel mailing list using
git format-patch or git send-email. Github pull requests should be
avoided because they are not part of our review process and will be ignored.