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

[Allen H.Y. Chin]

Rob,
Thanks a lot for your explanation, but I still have a question regarding 
"no lower bound".
>>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.
>

The CP L2 has a VCV decoder rate of 23760 MB/s,
which corresponds to twice CIF (its typical visual session size) at 30 Hz.
If encoder A can achieve real-time encoding rate higher than 23760 MB/s
(but it produce bitstream at a rate lower than 23760 MB/s for compliance),
can we say the encoder supports CP L2?
Encoder B is able to encode at a rate slightly lower than 23760 MB/s,
can we say it supports CP L2? Is it over-designed since it can not achieve
typical session size at 30Hz for CP L3?
Encoder C is able to encode at a rate slightly higher than 11880 MB/s,
can we say it supports CP L2?
Finally, if an encoder's max encoding rate is only 2970 MB/s or even worse,
can we say it supports CP L2?
Since encoders aren't standardized, and thus no lower bounds specified,
I'm confused about the meaning of "support" and why is there a "typical 
session size".
I thought that "typical session size" was a lower bound (for encoder).
Perhaps it's not a good way to classify encoders using Profile Level?
Instead, taking max encoding rate as a measure when comparing 
implementations might be a better choice?
Thank you again for your kind help.
Best regards,
Allen Chin