frame rate determination for h264 video capability in H323 video call

[conf_2008]

Hi Friends,

How do we determine maximum frames / sec supported by a conferencing endpoint for h264 video capability in a H323 video call?

Thanks!

[Joe Vallender]

The conferencing endpoint spec sheet should list its capabilities.

[conf_2008]

Is there any method to get this information from the parameters advertised by an endpoint in H323 signaling capability messages (Terminal Capability Set).

[Joe Vallender]

It might be available via the API interface of the endpoint.

[conf_2008]

In this case I don't have access to api of third party endpoint. What I've is h264 capability parameters advertised in H323 signaling messages. I am referring to H.241 ITU specification (Extended video procedures and control signals for H.300-series terminals) and parameters CustomMaxFS / CustomMaxMBPS.

[Sean Lessman]

In this case I don't have access to api of third party endpoint. What I've is h264 capability parameters advertised in H323 signaling messages. I am referring to H.241 ITU specification (Extended video procedures and control signals for H.300-series terminals) and parameters CustomMaxFS / CustomMaxMBPS.

CustomMaxFS and CustomMaxMBPS are two parameters you can use to increase the values of the Frame Size and MaxMBPS values if you can decode more than the values specified within the profile you support (i.e. level 2.1).

Important note, per the standard you can only increase the value specified within a profile (using Custom values), you cannot decrease the values.

Sean

[conf_2008]

Correct! but I am looking for a derivation using these parameters say how much frame / sec can an endpoint support for a particular resolution if it is willing to increase its video decoding capability.

[Sean Lessman]

Correct! but I am looking for a derivation using these parameters say how much frame / sec can an endpoint support for a particular resolution if it is willing to increase its video decoding capability.

That's a pretty complex question.

Simple minded people would say just translate MacroBlocksPerSecond to PixelsPerSecond and then throw in your resolution to determine your framerate. Unfortunately this method says nothing about instantaneous resolutions of those macroblocks, which is a huge factor in overall video quality. In other words, you can advertise 30fps of macroblocks, but the quality of the video can be crap. Be weary of anyone that tells you it is this simple.

The real answer depends on a number of simultaneous values that are always changing during the video call. We call it magic :)

Sean