[MPEGIF Discuss] AVC-derived scalable video coding?

[Robert Bleidt]

Perhaps I'm just adding confusion, but I'm guessing what you want is stream 
scalability, not scalable coding. Unless there's something new, (which I'd 
like to learn about), most of the proprietary codecs seem to use stream 
switching, not scalable coding.
To explain: (you might also take a look at the illustration in 
http://www.eet.com/story/OEG20011112S0043)
Generally, you can achieve scalable coding in three ways:
1. Switching from a stream to one encoded at a lower rate. (stream switching)
2. Dropping B-frames (temporal scalability)
3. Dropping enhancement layers (scalable coding or fine-grained scalability)
Scalable coding has the feeling of being the intellectually "right" way to 
do it, and gets a lot of interest from the research community. 
Unfortunately, in practice, as far as I know, it tends to work best over 
only a one-octave or so range of bitrates, after which the coding overhead 
of the enhancement streams starts to hurt the perceived quality. Stream 
switching doesn't have this efficiency loss and is fairly simple to 
implement - that's why it's used in practice. This is true both in audio 
and video coding - The BSAC audio codec using an coefficient encoding 
scheme very similar to the FGS profile of part 2 video.
I haven't done any work in this area, so I'm just repeating what I've heard 
and seen. Please voice your opinion...
Except for issues of switching streams (which the Extended AVC profile is 
supposed to have tools to address), there is no additional IP needed to do 
stream switching in AVC. There is room for innovation outside the standard 
in deciding when and how to switch streams.
At 02:15 PM 9/19/2003 -0700, you wrote:
>I've said for the while that the lack of a good scalable
>implementation is keeping MPEG-4 from being competitive in real-time
>streaming over the public internet.

Robert Bleidt   - www.streamcrest.com