[h323plus] Changing video codec transmit bit rate

Simon Horne s.horne at packetizer.com
Thu Nov 24 14:29:40 EST 2011


Unfortunately the OpenVideoChannel is called after the H.245 TCS stage so
you cannot use it to negotiate a bandwidth limit for a call.

To set the Initial Bandwidth limit in the TCS there is a callback which is
called when building.
H323EndPoint::OnSetInitialBandwidth(H323VideoCodec * codec);

So you could do something like this in your code

void MyH323EndPoint::OnSetInitialBandwidth(H323VideoCodec * codec) 
	unsigned bitrate = <your rate in kbps> * 1000;
	if ((bitrate != 0) && (codec->GetMediaFormat().GetBandwidth() >
bitrate)) {
		PTRACE(4,"My\tAdjusting maximum video bitrate to " <<

During a call the bitrate may change via FlowControl requests but will not
exceed the value you set in this callback.


-----Original Message-----
From: h323plus-bounces at lists.packetizer.com
[mailto:h323plus-bounces at lists.packetizer.com] On Behalf Of J C Mercier
Sent: 25 November 2011 05:08
To: h323plus at lists.packetizer.com
Subject: [h323plus] Changing video codec transmit bit rate

Hi all,

How would one go about adjusting the video codec max transmission bit rate?

I understand thus can be done in OpenVideoChannel by calling
codec.SetMaxBitRate but I I get  no flow control supported when I attempted
to do so.

I am using v 1.23 for H323plus downloaded from h323plus.org and pitlib v
2.8.5. I noticed that flow control is not supported in ptlib less than 2.9
but would there be another way of changing the bit rate?


Josh C.

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