[FFmpeg-devel] Scalable Video Encoding and FGS

Erik van Zijst ffmpeg
Fri Oct 19 20:44:17 CEST 2007

Michael Niedermayer wrote:
> On Thu, Oct 11, 2007 at 12:27:17PM -0700, Erik van Zijst wrote:
>> I think streaming video could also benefit from this platform/protocol 
>> when you apply some form of scalable encoding: have a small base-layer 
>> and multiple enhancement layers. I've looked at MPEG2 FGS which comes 
>> closest to my needs, but this has not been implemented in any serious 
>> codec AFAIK.
> no, and i think almost everyone is very glad that it hasnt, same for the
> equivalent mpeg4 scalability stuff
 > [...]
> also maybe b frames provide already enough scalability for your needs
> and they are fully supported on all decoders

I've considered layering on frame-type again (also comes up a lot in the 
research community), but I don't think it will be able to lower the 
bitrate significantly due to their relative sizes.

In MPEG1 b-frames are roughly 70 times smaller than i-frames [1], so 
cutting the bitrate in half, requires removal of 70 b-frames per i-frame 
(sure, these figures old and mpeg1-specific, but what matters is the 

So frame removal could be used to gain some scalability, but IMHO it 
cannot match the granularity of FGS and SVC.

"The typical data rate of an I-frame is 1 bit per pixel while that of a 
P-frame is 0.1 bit per pixel and for a B-frame, 0.015 bit per pixel." -- 

Jones' Motto:
	Friends come and go, but enemies accumulate.

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