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hashimoto.kotaro
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MCU transmit H.263+ instead of H.264

Hi all,

As you know, by configuring "Video transmit size optimization " as "Dynamic codec and resolution", MCU optimizes transmit video codec and transmit resolution.

But how does the MCU determine video codec?

I wonder why MCU transmits video with H.263+ to C20(TC4.2) even though the MCU receives video with H.264, and there seems to be no factor to degrade video codec(such as packet loss and so on).

Best Regards,

Kotaro Hashimoto

1 ACCEPTED SOLUTION

Accepted Solutions
Tomonori Taniguchi
Cisco Employee

What is bandwidth on call between MCU and C20?

Ideally MCU decrease the video resolution/code if the original size of the viewed video (especially with voice switch mode) is smaller than the outgoing video channel.

Also if the remote endpoint has use flow control and reduced the bandwidth on MCU main video transmission channel.

But also if call bandwidth is low, H.263 base with higher frame-rate (instead of H.264 base large video payload wit lower frame-rate) may choice as better experience video stream.

View solution in original post

6 REPLIES 6
Tomonori Taniguchi
Cisco Employee

What is bandwidth on call between MCU and C20?

Ideally MCU decrease the video resolution/code if the original size of the viewed video (especially with voice switch mode) is smaller than the outgoing video channel.

Also if the remote endpoint has use flow control and reduced the bandwidth on MCU main video transmission channel.

But also if call bandwidth is low, H.263 base with higher frame-rate (instead of H.264 base large video payload wit lower frame-rate) may choice as better experience video stream.

View solution in original post

Thank you for your reply, Taniguchi-san.

>What is bandwidth on call between MCU and C20?

I didn't write bandwidh and MCU setting.

Bandwidth between them is 2Mbps.

Participants on the call were only two, and "Use full screen view for two participants" setting was configured as "enable".

So both participants viewed full screen each other.

Does MCU degrade codec/resolution in this case?

Best Regards,

Kotaro Hashimoto

With 2Mbps call between MCU, MCU should stay with H.264 unless down speed during the call.

I assume you have already tested with motion/sharpness/auto setting and have same result…

If so, I’d recommend opening the TAC case and having a further investigation.

Just quick update, there is a known issue with certain MCU model and software version you may experience what you mention originally.

MCU developer team is looking this now.

For information please check at http://tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCtz58705.

Thank you for your reply Taniguchi-san.

The bug you informed us doesn't match in this case because our customer use MCU4520 (HD mode).

Anyway, for further investigation, we will open SR if our customer need.

Best Regards,

Kotaro Hashimoto

> With 2Mbps call between MCU, MCU should stay with H.264 unless down speed during the call.

Even then, H.264 offers better compression than H.263+ so it would not be sensible to choose to send H.263+ at lower bandwidth - in fact the opposite it true in that you would expect H.264 to be sent at lower bandwidths, where as H.263+ is more likely to be used at higher bandwidths.

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