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ATRAC3+ uses VLCs whose code lengths are ascending from left to right in the tree; ergo it is possible (and done) to run-length encode the lengths into so-called codebooks. These codebooks were variable-sized: The first byte contained the minimum length of a code, the second the maximum length; this was followed by max - min + 1 bytes containing the actual numbers. The minimal min was 1, the maximal max 12. While one saves a few bytes by only containing the range that is actually used, this is more than offset by the fact that there needs to be a pointer to each of these codebooks. Furthermore, since 5f8de7b74147e2a347481d7bc900ebecba6f340f the content of the Atrac3pSpecCodeTab structure (containing data for spectrum decoding) can be cleanly separated into fields that are only used during initialization and fields used during actual decoding: The pointers to the codebooks and the field indicating whether an earlier codebook should be reused constitute the former category. Therefore the new codebooks are not placed into the Atrac3pSpecCodeTab (which is now unused during init), but in an array of its own. The information whether an earlier codebook should be reused is encoded in the first number of each spectrum codebook: If it is negative, an earlier codebook (given by the number) should be reused. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.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 a mean to alter decoded Audio and Video through chain of 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.