On 2/27/22, Jack Bruienne <jackbruie...@gmail.com> wrote: > > From the wiki page (https://wiki.vexatos.com/dfpwm): >> DFPWM (Dynamic Filter Pulse Width Modulation) is an audio codec >> created by Ben “GreaseMonkey” Russell in 2012, originally to be used >> as a voice codec for asiekierka's pixmess, a C remake of 64pixels. >> It is a 1-bit-per-sample codec which uses a dynamic-strength one-pole >> low-pass filter as a predictor. Due to the fact that a raw DPFWM decoding >> creates a high-pitched whine, it is often followed by some >> post-processing >> filters to make the stream more listenable. > > It has recently gained popularity through the ComputerCraft mod for > Minecraft, which added support for audio through this codec, as well as > the Computronics expansion which preceeded the official support. These > both implement the slightly adjusted 1a version of the codec, which is > the version I have chosen for this patch. > > This patch adds a new codec (with encoding and decoding) for DFPWM1a. > The codec sources are pretty simple: they use the reference codec with > a basic wrapper to connect it to the FFmpeg AVCodec system. > > To clarify, the codec does not have a specific sample rate - it is > provided by the container (or user), which is typically 48000, but has > also been known to be 32768. The codec does not specify channel info > either, and it's pretty much always used with one mono channel. > However, since it appears that libavcodec expects both sample rate and > channel count to be handled by either the codec or container, I have > made the decision to allow multiple channels interleaved, which as far > as I know has never been used, but it works fine here nevertheless. The > accompanying raw format has a channels option to set this. (I expect > most users of this will not use multiple channels, but it remains an > option just in case.) > > This patch will be highly useful to ComputerCraft developers who are > working with audio, as it is the standard format for audio, and there > are few user-friendly encoders out there, and even fewer decoders. It > will streamline the process for importing and listening to audio, > replacing the need to write code or use tools that require very > specific input formats. > > You may use the CraftOS-PC program (https://www.craftos-pc.cc) to test > out DFPWM playback. To use it, run the program and type this command: > "attach left speaker" Then run "speaker play <file.dfpwm>" for each file. > The app runs in a sandbox, so files have to be transferred in first; > the easiest way to do this is to simply drag the file on the window. > (Or copy files to the folder at https://www.craftos-pc.cc/docs/saves.) > > Sample DFPWM files can be generated with an online tool at > https://music.madefor.cc. This is the current best way to encode DFPWM > files. Simply drag an audio file onto the page, and it will encode it, > giving a download link on the page. > > I've made sure to update all of the docs as per Developer§7, and I've > tested it as per section 8. Test files encoded to DFPWM play correctly > in ComputerCraft, and other files that work in CC are correctly decoded. > I have also verified that corrupt files do not crash the decoder - this > should theoretically not be an issue as the result size is constant with > respect to the input size. > > Changes since v4: > Fixed missing channel check in decoder. > > Changes since v3: > Added support for multiple interleaved channels, and cleaned up the > code a bunch. > > Changes since v2: > I've found that the reference encoder has a few errors, and sounds > worse than the Java-based implementation that is used most often. I got > in contact with someone who knows DFPWM much better than I do, and I > worked with them to make a few adjustments that should improve the > audio quality. I also made sure that the output matches the Java > codec exactly, so it should have the exact same quality as other codecs. > > Signed-off-by: Jack Bruienne <jackbruie...@gmail.com> > --- > Changelog | 1 + > MAINTAINERS | 1 + > doc/general_contents.texi | 1 + > libavcodec/Makefile | 2 + > libavcodec/allcodecs.c | 2 + > libavcodec/codec_desc.c | 7 ++ > libavcodec/codec_id.h | 1 + > libavcodec/dfpwmdec.c | 133 ++++++++++++++++++++++++++++++++++++++ > libavcodec/dfpwmenc.c | 121 ++++++++++++++++++++++++++++++++++ > libavcodec/utils.c | 2 + > libavcodec/version.h | 2 +- > 11 files changed, 272 insertions(+), 1 deletion(-) > create mode 100644 libavcodec/dfpwmdec.c > create mode 100644 libavcodec/dfpwmenc.c > >
Please move channel check to init. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
