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The FDK decoder is capable of producing mono and stereo downmix from multichannel streams. These streams may contain metadata that control the downmix process. The decoder requires an Ancillary Buffer in order to correctly apply downmix in streams containing downmix Metadata. The decoder does not have an API interface to inform of the presence of Metadata in the stream, and therefore the Ancillary Buffer is always allocated whenever a downmix is requested. When downmixing multichannel streams, the decoder requires the output buffer in aacDecoder_DecodeFrame call to be of fixed size in order to hold the actual number of channels contained in the stream. For example, for a 5.1ch to stereo downmix, the decoder requires that the output buffer is allocated for 6 channels, regardless of the fact that the output is in fact two channels. Due to this requirement, the output buffer is allocated for the maximum output buffer size in case a downmix is requested (and also during decoder init). When a downmix is requested, the buffer used for output during init will also be used for the entire duration the decoder is open. Otherwise, the initial decoder output buffer is freed and the decoder decodes straight into the output AVFrame. Signed-off-by: Martin Storsjö <martin@martin.st>
Libav
Libav 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.libavresampleimplements audio mixing and resampling routines.libswscaleimplements color conversion and scaling routines.
Tools
- avconv is a command line toolbox to manipulate, convert and stream multimedia content.
- avplay is a minimalistic multimedia player.
- avprobe is a simple analisys 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
Conding examples are available in the doc/example directory.
License
Libav codebase is mainly LGPL-licensed with optional components licensed under GPL. Please refer to the LICENSE file for detailed information.