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VP6 alpha in EA format is a second VP6 encoded video stream where only the Y
component is used and is interpreted as the alpha channel of the first VP6
stream. The alpha VP6 stream is muxed separately from the main VP6 stream, has
its own stream headers and packet headers. In theory the two streams might not
even have the same resolution (although most likely that is not something that
is seen or supported in the wild), but the format is capable of doing it.
Merged VP6 alpha (also known as the VP6A codec) means that a packet of the
video stream contains the corresponding packet of both VP6 substreams like
this:
{OffsetOfAlpha, DataPacket, AlphaDataPacket}
So data and alpha data of a frame is merged to a single packet, this is how VP6
video with alpha is muxed in FLV and SWF.
The first approach is more like how the demuxer sees data in the EA format,
unfortunately it is different to what the FLV or SWF format expects, so -
having no better place for it in the framework - I decided to do an optional
format conversion in the EA demuxer.
Signed-off-by: Marton Balint <cus@passwd.hu>
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.