theora dev - May 2005 - Problems with Theora alpha 4 crashing

Hi,

I havent posted to this list before, so "hi"

I have been experimenting with Theora and noticed it still has the
same crash bug that VP3 did.

Basically, if you begin compression, and compress a blank black frame
more than about twice in a row you get a Div by 0 error.

I traced the fault to being in the "RegulateQ" function, and is
because YUVAnalyseFrame() returns 0 for the motion score.

With VP3 I was able to resolve this by changing this value to 1 if
this happened and that seemed to work fine.

Thought I'd let you know.  May help the encoder to be even better!

Regards

Rob Smith

On Sun, May 01, 2005 at 01:08:07PM +0100, Rob Smith wrote:
> I havent posted to this list before, so "hi"
Hello!
> I traced the fault to being in the "RegulateQ" function, and is
> because YUVAnalyseFrame() returns 0 for the motion score.
> 
> With VP3 I was able to resolve this by changing this value to 1 if
> this happened and that seemed to work fine.
Aha, thanks for pointing this out. Clamping the UpdateScore to 1 is a 
reasonable approach. I don't actually get a floating point exception, 
it's just that the target bitrate gets calculated as infinity.

Derf committed a change to just not update Q if the Score is zero. 
Hopefully this will help with some of popping artefacts we've been 
seeing.

 -r