Thursday, 28 March 2013

jjmpeg android hardware decoding

I somewhat embarassingly just discovered that FFmpeg already has some support for using libstagefright for hardware video decoding on Android.

I always thought this was the place it should go, since mucking around with OMX or other junk is just such a pain, and it belongs there.

Bit of a headfuck getting it to compile, particularly since this adds a C++ dependency, and then after all that ... it just crashes.

I/ffmpeg  (10484): Assertion i < avci->buffer_count failed at
F/libc    (10484): Fatal signal 11 (SIGSEGV) at 0xdeadbaad (code=1), thread 10607 (VideoDecoder)
I/DEBUG   ( 1894): *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
I/DEBUG   ( 1894): Build fingerprint: 'samsung/m0zs/m0:4.1.2/JZO54K/I9300ZSEMB1:user/release-keys'
I/DEBUG   ( 1894): pid: 10484, tid: 10607, name: VideoDecoder  >>> au.notzed.jjmpeg <<<
I/DEBUG   ( 1894): signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr deadbaad
I/DEBUG   ( 1894):     r0 00000027  r1 deadbaad  r2 40126b0c  r3 00000000
I/DEBUG   ( 1894):     r4 00000000  r5 620f2a04  r6 60bfcc00  r7 61d0b8b0
I/DEBUG   ( 1894):     r8 5b127c80  r9 61bd5718  sl 000104d5  fp 61bd5718
I/DEBUG   ( 1894):     ip 5dc4bcbc  sp 620f2a00  lr 400f8c65  pc 400f52fe  cpsr 60000030
I/DEBUG   ( 1894):     d0  0000000200000000  d1  4b0000004b000021
I/DEBUG   ( 1894):     d2  000000094b000021  d3  0000000000000000
I/DEBUG   ( 1894):     d4  3ce5999061da5385  d5  3f34e1653f349a33
I/DEBUG   ( 1894):     d6  3f35287b3f356f75  d7  0106999ec0000000
I/DEBUG   ( 1894):     d8  0000000000000000  d9  0000000000000000
I/DEBUG   ( 1894):     d10 0000000000000000  d11 0000000000000000
I/DEBUG   ( 1894):     d12 0000000000000000  d13 0000000000000000
I/DEBUG   ( 1894):     d14 0000000000000000  d15 0000000000000000
I/DEBUG   ( 1894):     d16 8000000000000000  d17 ffffffffffffffff
I/DEBUG   ( 1894):     d18 416347d4c0000000  d19 3fe0000000000000
I/DEBUG   ( 1894):     d20 3fe0000000000870  d21 0000000000000000
I/DEBUG   ( 1894):     d22 0000000000000000  d23 0000000000000000
I/DEBUG   ( 1894):     d24 0000000000000000  d25 0000000000000000
I/DEBUG   ( 1894):     d26 0000000000000000  d27 0000000000000000
I/DEBUG   ( 1894):     d28 3f3504f3bf3504f3  d29 bf3504f33f3504f3
I/DEBUG   ( 1894):     d30 0000000000000000  d31 3f3504f33f3504f3
I/DEBUG   ( 1894):     scr 20000010

So yeah, i dunno. Perhaps it is a bug in jjplayer, but I tried removing all output handling, and it still just crashes inside codec->decode(), and the api to that point is so simple I don't think I can screw it up.

I've wasted half a day on this and it's losing it's interest very fast ...

Update: So, just when I was about to give up, I found a threading bug in the codec implementation. This at least lets it decode more frames but it's still crashing later on inside the GLES library.

I haven't got the NV21 image format working properly yet, so it may be related to that, maybe.

Update: Well that was pretty much a full day down the drain, I submitted a patch to the ffmpeg-devel mailing list (yay, subscribe to a high volume list of zero interest to me just to submit a 10 line patch).

It turned out that the file I was testing against refuses to play at all in the bundled players, so it's something to do with the hardware/firmware. At best they load the first frame then abort, although they don't segfault (probably the parser/demux stops it going as far as the codec).

On a video recorded from the camera it seems to work ok, although it certainly doesn't appear particularly smooth - I would need to do some timings to see what's going on. I haven't written the NV21 support either. And the build stuff needs cleaning up and parameterising before I can check it in.

If it's going to still be so useless i'm not sure I really care to be honest. And I've had more than enough for today so whatever I decide will have to wait.

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