Friday, 4 May 2012


So yesterday I checked in the work I did last week for the android jjmpeg port. Not heavily tested, but it appears to work.

Then I spent far too long poking around trying to find out about the EGL OES_external_images extension, but finally came to the conclusion that it just isn't exposed publicly (yet?) so it's way more effort than it's worth to me to get it going.

So I suppose it's just glTexSubImage2D for me then.


I had a long work week this week and although I had intended to get a couple more things out of the way this morning I let it slide, and eventually got sucked in to playing with jjmpeg. I rigged up a version using GL, but still for now performing CPU-side colour conversion. I at least added a separate thread to do the colour conversion, and hooked it all up so that nothing needs to wait for anything else unless absolutely necessary.

The display stuff is a little bit faster - but nothing to worry about TBH. The colour conversion is only about 20% of the time, so it isn't a real big difference either.

I also tried with/without VFP: which made stuff all difference too, barely 5%. I started with 32-bit RGB textures simply because I had that already, and changed those to RGB565 which made another small difference. But all these small differences just weren't adding up to anything but a lot of small differences.

So anyway ... I went and looked at some of the options for skipping frames, multi-threaded decoding and what have you, and I noticed that threading wasn't enabled in the build.

Cut a long story short - beware of copies of copies of scripts one finds on the net: my compile script was basically shit. I also turned on NEON this time ...


I'm not sure if it's just the NEON, or the threads - or simply compiling it properly - but boy what a difference.

(actually it's all those not-so-little-bits now adding up, even single-threaded it's now much faster, in performance mode 2 threads can nearly handle 720p).

So it's now decoding 720p MP4 fine (taken from the on-board camera), even in 'balanced power saving' mode. Before it was struggling with this, under 10fps. And now the colour conversion is more like 50% of the time, so I will have to investigate using GLES for this since it should be a lot better at it.

Anyway, i'm quite chuffed at this now - I was starting to think it was pretty much pointless apart from perhaps encoding or more control over decoding. But this level of performance opens up a lot of possibilities. I'm also still only using ffmpeg 0.10.0 release, so there might be more there now too.

Update: So I kept going and added the GL colour conversion. Quite a bit better and 720p is fine with 2 threads, but not able to handle 1080P from the built-in camera.

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