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Michael Zucchi

 B.E. (Comp. Sys. Eng.)

  also known as Zed
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Monday, 31 December 2012, 23:07

jjmpeg android video player work

Yesterday I was too lazy to get out of the house, so after getting over-bored I fired up netbeans and had a poke at the android video player JJplayer again.

And now it's next year.

I tried a few buffering strategies, copying video frames, loading the decoded frames directly with multiple buffers (works only on some decoders), and synchronously loading each decoded frame into a texture as it is decoded. I previously had some code to load the texture on another GL context but I didn't see if it still worked (it was rather slow which is why i let it rot, but it's probably worth a re-visit).

Just copying the raw video frame seems to be the most reliable solution, even with it's supposed overheads. Actually it didn't seem to make much difference to performance how I did it - they all ran with similar cpu time (according to top).

I've looked into doing the scaling/yuv/rg565 conversion in NEON but haven't got any code up and running yet (one has to be a bit keen to get stuck into it). I doubt it will be quicker as this means I wont be using the GPU for this processing, but given how slow the texture loading is it might be a win and it will let me avoid redundant copies.

I also fixed some of the android behavioural stuff - pause/resume pauses/resumes the playback, it runs in full-screen with a hidden 'ui' (although for whatever reason, setting the slider to invisible doesn't always work, and never on the mele), and it now opens the video in another thread with a busy spinner.

Although it's playing back most SD sized videos ok on my (dual core) ainol tablet, it is struggling on the mele. Even when the mele can decode fast enough the timing is funny - jumping around (and oddly, the load average is well over 2 yet it decodes all frames fast enough). I guess the video decode was behind the audio so it was just displaying frames as fast as it decoded them rather than with per-frame timing. So I tried another timing mechanism rather than just using an absolute clock from the first frame decoded, have it based on the audio playback position. This works quite a bit better and lets me add a tunable delay, although it isn't perfect. It falls down when you seek backwards, but otherwise it works reasonably well - and should be fixable. OTOH even with the busted timing the audio sync was consistent - unlike Dolphin Player which loses sync quite rapidly for whatever reason.

Unfortunately opening some videos seems to have become quite slow ... not sure what's going on there, whether it's just slow i/o or some ffmpeg tunable (I was poking around with some other stuff before getting back to jjplayer so i might've left something in). I don't know how to drop the decoding of video frames yet either - which would be useful. I think I need to add some debugging output to the display to see what's going on inside too, and eventually run it in the profiler again when I have most of a day free.

The code is still a bit of a pigs breakfast and I haven't checked it in yet. But i should get to it either today or soon after and will update the project news. I should probably release another package too - as the current one is too broken to be interesting.

In the not too distant future I will probably poke at a JavaFX version as well. If I don't find something better to do ... must really look at the Eiphany SDK sometime.

Tagged android, hacking, jjmpeg.
NEON yuv + scale | 50K
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