[FFmpeg-devel] Scalable Video Encoding and FGS

Michael Niedermayer michaelni
Thu Oct 11 23:23:37 CEST 2007


On Thu, Oct 11, 2007 at 12:27:17PM -0700, Erik van Zijst wrote:
> Hi folks,
> It seems every once in a while someone comes along asking for Scalable 
> Encoding support (FGS, SNR, SVC, etc), often because they want to do 
> fancy video streaming. I guess this time it's my turn :-)
> Some time ago I built a wide-area publish/subscribe platform targeted to 
> live data streaming over unreliable, fluctuating networks (wifi, 
> Internet, etc) that are inherently hostile to live streaming.
> This platform works by first slicing up the stream in prioritized 
> logical layers, send these over the network and let the network drop 
> low-priority layers during congestion, instead of buffering. The result 
> is a client that never has to wait or re-buffer even during heavy 
> congestions. Works really great for real-time streaming financial data 
> (high-volume stock quotes).
> 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

have you considered using several streams where each is optimized for a
specific bitrate and then just switch between them depending on network
state or even encode a stream in realtime depending on the available
also you should keep in mind that all the scalability stuff will be
worse quality per bitrate than streams optimized for a single bitrate

also maybe b frames provide already enough scalability for your needs
and they are fully supported on all decoders

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Everything should be made as simple as possible, but not simpler.
-- Albert Einstein

PS: i love my random quotes, this one really is appropriate here ...
PS2: iam of course not against adding FGS/... support to ffmpeg if someone
submits a VERY clean patch which also can be disabled at compile time
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