[XviD-devel] Buffering in the decoder or encoder.

Michael Militzer michael at xvid.org
Wed Sep 7 21:20:28 CEST 2005


Hi,

your overall set-up is not really clear to me yet. But in case you are
transmitting video over a network (which it seems like you do), this could
also be a cause of delay. If you set a target bit-rate in the encoder that
approx. matches your available network bandwidth, then you should take 
into account that this desired bit-rate isn't always perfectly achieved.
So there could be bit-rate peaks (e.g. for key-frames) in which case your
network won't be able to deliver the frame in-time to the decoder, so delay
will occur.

You could try setting the 'reaction_delay_factor', 'averaging_period' and
'buffer' variables in xvid_plugin_single_t to low values and see if that
helps to reduce your delay. However, if your aim is ultra low-delay
transmission, then probably even a new rate-control would have to be used
as the current rate-control implementation in XviD is more optimized for
storage and does not perfectly fit low-delay communications.

Bye,
Michael


Quoting "Yong, Chee Yeew " <Chee-Yeew.Yong at thalesgroup.com>:

> Is it possible then, that the MPEG-4 algorithm (if you can call it that)
> needs to buffer frames before decoding (or encoding) them? I am not familiar
> with the MPEG-4 algorithm, and I hope that someone here can suggest if this
> is true or not.
> 
> Thanks.
> Chee
> 
> -----Original Message-----
> From: Yong, Chee Yeew [mailto:Chee-Yeew.Yong at thalesgroup.com]
> Sent: Monday, September 05, 2005 5:07 PM
> To: 'Alexander Strange'
> Cc: xvid-devel at xvid.org
> Subject: RE: [XviD-devel] Buffering in the decoder or encoder.
> 
> 
> Indeed, we are already using max_bframes=0.
> 
> -----Original Message-----
> From: Alexander Strange [mailto:astrange at ithinksw.com]
> Sent: Monday, September 05, 2005 4:57 PM
> To: Yong, Chee Yeew
> Cc: xvid-devel at xvid.org
> Subject: Re: [XviD-devel] Buffering in the decoder or encoder.
> 
> 
> 
> On Sep 5, 2005, at 11:40 AM, Yong, Chee Yeew wrote:
> 
> > Hello all,
> >
> > We are using the Xvid library to do real-time interactive  
> > communications.
> > Therefore, we are very concerned with some delay that we are  
> > finding. We
> > have narrowed down the delay (in the 100-200ms region) to the Xvid  
> > library,
> > but the problem is we do not know whether it is the encoder or  
> > decoder.
> > We deduce that it is the decoder since the encoder should only ever  
> > need to
> > work with 1 frame (no buffering needed).
> 
> This of course depends on the settings being used. I assume you don't  
> have B-frames enabled, but if you do, disable them (max_bframes = 0)  
> in the encoder.
> 
> 
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