Saturday, April 25, 2009

Lessons from LAC

I was at the Linux Audio Conference in Parma/Italy. The weather sucked most of the time, but everything else was great. These are the most important things I learned:

Jack rules
Of course I already heard about the Jack sound system before. But since I never had a linux distribution, which installs jack by default, I didn't pay much attention to it.

If you go to the LAC, you start to think that there is hardly any audio architecture besides jack. After looking a bit into Jack (and writing gmerlin plugins for Jack audio I/O) I learned, that it's actually pretty cool. I like especially the way, you can connect arbitrary jack applications together while they are running. This is a nice feature for the gmerlin-visualizer since it relies on grabbing the audio stream from another application.

Ambisonics rocks
I also heard about Ambisonics before but mostly ignored it. If you read the Wikipedia article, you get the impression, that ambisonics is a quite exotic recording/playback technique, which is used only by a small group of enthusiasts.

If you go to LAC, you get the impression that Ambisonics is the standard and things like stereo or 5.1 are quite exotic recording/playback techniques, which are used only by a small group of enthusiasts.

Audio vs. video development
I told the audio developers that they don't know how lucky they are. They agreed on an audio capture/playback architecture (jack), they all use the same internal format (floating point, not interleaved) for processing and they manage to make a conference each year.

In the video area, things are much worse. Capture and playback APIs exist, but they are far too many. Some people do internal processing in RGB, others prefer Y'CbCr. Converting to a common internal format is not feasible because video has much higher data rates than audio and conversion overhead must always be minimized. Also the video developer community is very fragmented, centered around different frameworks (each one being the standard). Cross project communication is sparse. The only common code is ffmpeg for video en-/decoding, but mostly because nobody wants to reimplement such a beast.

Gmerlin development
I talked a lot with Richard Spindler from the openmovieeditor, which makes heavy use of gmerlin libraries. We agreed that our collaboration works quite well because the development activities of gmerlin and openmovieeditor are nicely decoupled. Let's proceed like we already did.

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