[x264-devel] x264 crosses video information when numerous encoders running in multiple threads

anton kropp akropp at gmail.com
Sun Jan 25 01:17:05 CET 2009

Loren, thanks for the reply.  This has been causing me a bunch of
grief in the last week once I realized what was happening.  I'm not
very familiar with the inner workings of x264, however, do you have
any suggestions of where I can try to debug this issue within the
code?  I have 2 320x240 video streams and 1 1024x768 video stream and
its most apparent in the larger stream. Sometimes it also seems that
x264 is dropping a keyframe, though I'm not sure if this has to do
with the reentrant issue or not.


On Sat, Jan 24, 2009 at 6:41 PM, Loren Merritt <lorenm at u.washington.edu> wrote:
> On Fri, 23 Jan 2009, anton kropp wrote:
>> Basically I have several video streams coming in from different
>> sources all going to individual x264 encoding threads.  However, on
>> output there are lots of artifcats, and if I pause my saved videos
>> during these artifcats, I can actually see small segments of video's
>> that come from other threads.  I've made sure that I'm not crossing
>> any thread information myself and I am confident that somewhere x264
>> is statically storing information. Has anyone else ever encountered
>> this or have a fix?
> x264 is intended to be reentrant, but as far as I know it's never been
> tested before. I don't know of any published program that uses multiple
> instances of x264, let alone from multiple threads.
> `nm libx264.a | grep -wi '[bd]'` shows only some tables that are run-time
> initialized but constant thereafter.
> --Loren Merritt
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