[Mp4-tech] Question about definition of Profiles@Levels for VisualEncoder

[Rob Koenen (MPEGIF)]

Allen,
> Is it correct to say a compliant encoder produces bit stream that do not
> exceed the max values of Video Buffering Verifiers?

It is correct to state that any bitstream that does not exceed these
bounds is compliant. It is hard to talk about compliant encoders, because
encoders aren't standardized, but in general one could say that any
decoder is compliant if it only produces compliant bitstreams.
> And what are the lower bounds for certain Profile Level? it 
> it the upper bound of the lower level?

There are no lower bounds for encoders / bitstreams. A compliant decoder
must at minimum be able to decode all compliant bitstreams. In general, 
again, a conformance point gives a maximum complexity for bitstreams (and
thus encoders), and minimum performance measures for decoders. Think of
it as a bar - the decoder must be above the bar, the bitstreams (and 
encoder) must remain below the bar.
Best,
Rob