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Opus can be decoded to multiple samplerates (namely 48kHz, 24KHz, 16Khz, 12 KHz and 8Khz); libopus as well as our encoder wrapper support these sample rates. The OpusHead contains a field for this original samplerate. Yet the pre-skip (and the granule-position in the Ogg-Opus mapping in general) are always in the 48KHz clock, irrespective of the original sample rate. Before commitc3c22bee63, our libopus encoder was buggy: It did not account for the fact that the pre-skip field is always according to a 48kHz clock and wrote a too small value in case one uses the encoder with a sample rate other than 48kHz; this discrepancy between CodecDelay and OpusHead led to Firefox rejecting such streams. In order to account for that, said commit made the muxer always use 48kHz instead of the actual sample rate to convert the initial_padding (in samples in the stream's sample rate) to ns. This meant that both fields are now off by the same factor, so Firefox was happy. Then commitf4bdeddc3cfixed the issue in libopusenc; so the OpusHead is correct, but the CodecDelay is still off*. This commit fixes this by effectively revertingc3c22bee63. *: Firefox seems to no longer abort when CodecDelay and OpusHead are off. 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.