[libav-devel] Quick notes from the Tech Meeting held at the VDD

Sean McGovern gseanmcg at gmail.com
Mon Nov 13 19:02:58 CET 2017

Hi all,

On Sep 26, 2017 07:55, "Luca Barbato" <lu_zero at gentoo.org> wrote:

Here some point-lists with a really coarse summary based on Sean's notes
and my editing.

TL;DR: New major release within 3 months, help welcome!


• Sean McGovern (note taker)
• Maxym Dmytrychenko
• Mark Thompson
• Diego Biurrun
• Anton Khirnov
• Luca Barbato
• Martin Storsjö
• Janne Grunau
• Vittorio Giovara
• Yogender Gupta
• Vladimir Pantelic

Conversation points:
• release/13 Coming soon (January?)
    Features we definitely want:
    • MVC (Anton), almost done, discussion on how to signal the view
      a frame belongs.
    • OpenCL/CUDA filters (Yogender, Mark), work mostly done, pending
      review and eventual merge. Some concerns on when and where the
      cuda kernels are compiled. npp should be deprecated in favour of
      CUDA filters due libnpp limitations/inflexibility.
    • VPP (Maxym), the bulk of it is already in, some work pending
      (see my patch about joining sessions for an example)
    • Get VLC to use newer hwaccel interface (Anton), would make easier
      to drop the legacy cruft.
    • CUVID Decoding (Anton), according to Yogender it is fine already.
    • Better hw accelerated filter chains (Luca, Mark, Anton, Yogender),
      currently you have to rely on tutorials to get the chain right
      • friendlier error messages to explain what to do (Mark)
      • explicit h/w contexts (Mark, Luca, Anton), nice to have but
        not necessary, requires more work
      • shortcuts for commonly used filters chains (Luca)
    • Audio layout (ambisonics and friends) work (Vittorio, Anton),
      a final review started after the meeting.
    • Display mastering metadata (Vittorio), the feature proposed by
      Steve requires some overhaul before landing.
    • avplay: time for migrating to SDL2? (Luca), SDL1.2 is pretty much

    On the fence:
    • Single-in multi-out codec handling (Luca), is needed to leverage
      the new x265 API to output multi-bitrate streams in a single pass,
      shouldn't be much work but needs testing and have Pradeep to confirm
      how it is supposed to work.
    • Complete the deployment of new bitstream reader (Diego, Anton),
      Few codecs are missing, devoting some time to find and remove the
      slowdown seems the best path.

• release/14 Items (what needs more time and won't fit 13)
    • Provide better handling of codec reconfiguration (Luca), possibly
      add some options in avconv to generate chapters or even cut the file
      (requires some overhaul to the chapter API).
    • Rewrite YADIF from scratch (Anton), some assumptions made while that
      code was written are going to not apply anymore.
    • Move the I/O to libavio and overhaul it (Luca), Martin pointed out
      that before that the RTP/RTSP layer should be reworked.
    • Is libavdevice still useful? (Anton), it is mainly for capture while
      playback tends to have enough issues regarding syncronization that
      make it less usable than it should.
      • different API (Anton), probably it should not try to fit avformat.
      • avgrab? (Anton), a separate tool might be nice to have.

• Are we missing any hardware acceleration library support? (Anton)
    • VideoToolbox on MacOS (Luca)
    • AMD-specific (Luca)
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It's been almost 2 months since VDD -- have we made any head-way on these?

Are any of them able to be finished in short order? Like say the SDL2

Has anyone talked to the VLC people about the newer hwaccel stuff at least?

Sorry for being a bit of a nag,
-- Sean McG.

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