[theora-dev] dynamic change video quality........

Asanka Dilruk adilruk at gmail.com
Tue Feb 19 04:17:43 PST 2008

Hi monty..
   Actually i wanted to change video quality according to the available
bandwidth of the network to get better streaming performance. So i thought
if i can change video quality value to do that. can i change video quality
value frame by frame.

On Feb 19, 2008 2:47 PM, <xiphmont at xiph.org> wrote:

> On Feb 19, 2008 1:06 AM, Asanka Dilruk <adilruk at gmail.com> wrote:
> > I am going to change video quality parameter frame by frame.
> There is currently no way to do this as there's no API.  You'd have to
> reach directly into the internal code (which is, of course, what you
> are suggesting), but this will be unstable.  Eg, once the Thusnelda
> changes are merged back to mainline, this strategy will break.  The
> symbols will not even be exposed in normal lib builds. Also, for what
> you've described, you want to be influencing the bitrate management
> parameters, not the quality parameter.
> Anyway, I can see the use of this functionality, so I will see to
> adding it to the API.  Derf, do you have documentation of your new API
> so that I can do this correctly...?
> > So i find a
> > parameter called thisframequalityvalue for this task. so i changed
> > cpi->Configuration.ActiveMaxQ(set "1" for half of the frames and set
> "63"
> > for other half of frames) manually to change thisframequalityvalue
> parameter
> > in UpdateFrame frame function. But quality was not changed. Why is
> > that..
> Because that's an internally computed value, and it is recomputed for
> each frame internally regardless of what you set it to outside.  All
> you're doing is accidentally clobbering the value of
> LastFrameQualityValue, which will cause the internal regulation to go
> haywire.  I'm not sure why you'd think that would do what you want...
> Monty

Asanka Dilruk
Department of Computer Science and Eng.
University of Moratuwa....
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