[x264-devel] non deterministic encoding

[Emanuele Fumagalli]

Hi all,
I'm trying to encode an mp4 container with mpeg4 as video track and aac as 
audio, I'm using x264 and I noticed that the result has a non deterministic 
behaviuor, I mean sometimes the x264 cannot converge and the result has a 
lower bitrate than the one specified.

The thing is that if I run several times the encoding without changing 
anything I don't get all the time the result I need.

Has anyone some idea about that?
Could it be connected to the threads "auto" parameter?
Or to the profile, I'm using a Baseline profile?

here's the details (I use ffmpeg -i to get them, is something better?)

Container: mp4

Duration: 1min 5 sec

bitrate 895 kb/s

videotrack : mpeg4, yuv420p, 320x240, 25.00 fps
audio: aac, 44100 Hz, stereo

I encode through an avisynth script:
DirectShowSource("filename")
ConvertToYV12()

And two pass x264 (just the latest build 664)

--pass 1 --bitrate 410 --no-cabac --progress --no-psnr --subme 1 --analyse 
none --me dia --ref 1 --threads auto

--pass 2 --bitrate 410 --no-cabac --analyse p8x8,b8x8,i4x4,p4x4 --subme 
6 --progress --no-psnr --threads auto

Then on some occasions I get the bitrate of the encoded aroun 190 kb/s

thanks for any help 

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