[FFmpeg-devel] [RFC] avcodec: Add native DCA decoder based on libdcadec.

James Almer jamrial at gmail.com
Sun Jan 3 19:24:22 CET 2016

On 1/3/2016 2:49 PM, foo86 wrote:
> This is initial version of libdcadec DCA decoder port I hacked together over
> the last week. This patch is of RFC/inquiry type and not meant for immediate
> inclusion.
> Any comments about the code are appreciated, as well as suggestions concerning
> how should I proceed with this patch. Should I aim for including it as a
> separate decoder or a replacement for existing DCA decoder? Or it might be that
> you prefer to continue improving existing decoder instead and not merge this at
> all.

IMO this should replace the current dca decoder. Based on what i saw from libdcadec
yours is cleaner, more feature complete, you're a knowledgeable maintainer, and
since the current developer for ffdca over at libav is porting code from yours to
get bitexact xll working the code duplication would be considerable if we keep both.

> Attached decoder is feature complete enough to fully decode any practically
> available DTS stream configuration. It supports any possible combinations of
> XCH, XXCH, XBR and X96 core extensions to deliver up to 7.1 ch, 96 kHz floating
> point output. It also implements lossless decoding of XLL extension to deliver
> up to 7.1 ch, 192 kHz fixed point output. Bit rate managed XLL streams are
> supported. Downmixing to 5.1 and stereo using embedded coefficients is
> supported.
> Performance wise, this decoder used to be around 10% slower than pure floating
> point version of existing native DCA decoder. However, after native DCA decoder
> has been partially converted to fixed point, this decoder became 5% faster than
> native one. Measurements were done looping over 5.1 core only stream in

Another reason to have this replace the current one, then.


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