[h323plus] Video Resolution

Simon Horne s.horne at packetizer.com
Fri Jan 15 13:05:25 EST 2010

Maybe I should rephase my last email
The old openH323 behaviour in the OpenVideoChannel allowed the user to
safely set the webcam framesize to the default size of the codec because it
was always fixed. So if your codec was CIF webcam was CIF. So that is why
QCIF/CIF in both directions works. Now you have changed the frame size of
CIF capability to QCIF in the codec it won't. Why? You must make sure in
your code the framesize coming out of the VideoInputdevice when you create
it is set to QCIF otherwise it will be CIF and the encoder will expect QCIF
and that is why you are getting the codec encoder call returning 0 and the
channel being closed down.
Did I miss something?


From: Carlos Haj [mailto:unazona at hotmail.com] 
Sent: Saturday, 16 January 2010 3:24 AM
To: s.horne at packetizer.com; h323plus at lists.packetizer.com
Subject: RE: [h323plus] Video Resolution


I used fixed width and height to determine display and reader working, and I
traced again my application.

This time I went deeper into the h323plus library, I think it's a bug of
h323plus, between the library and the video codec plugin.

Bug Scenario:

I have set 

    AddAllCapabilities(0, P_MAX_INDEX, "*");

I only use H261 this time


Set the maximum Frame size and send a kind of parameter cifTag to the plugin

on my OnVideoChannel I initialise 

if (encoder) 
       codec.SetFrameSize(176, 144);

This is the call stack by chronological order for an h323 video call using a
CIF<->QCIF endpoint (trace is for endpoint that sending qcif)

1) H323PluginVideoCodec::H323PluginVideoCodec(...)

it creates the encoder, and set frame size to CIF (the default plugin
maximum value)

2) H323PluginVideoCodec::SetFrameSize(...)

it adjusts the frame size, called from my OnVideoChannel, with qcif Value

3) H323PluginVideoCodec::Read(...)

All work, my rawChannel, renderer, etc... until I reach line 1690

H323pluginmgr.cxx::1690 - THE FIRST READ call to encode video fails

    int retval = (codec->codecFunction)(codec, context, 
                                        bufferRTP.GetPointer(), &fromLen,
                                        dst.GetPointer(), &toLen,

retval = 0, which results into closing the channel as it returns false,

if I change SetVideoFrameSize(H323Capability::cifMPI); into

The codec function works again, but naturally with qCIF on both sides

I think that once the codec parameter was tagged to use a cif or a qcif it
can't change resolution during the call. so the encoding function fail for a
resolution different than one setted using the SetVideoFrameSize.

It's likely that the SetVideoFrameSize send an additional information to
plugin code using a setcontrolcodec which are required later so the encoding
function works properly.

I noticed, that video resolution fail is only a local behaviour, and has
nothing to do with remote endpoint.

I will be debugging more, I still don't know the plugin code so much, so you
might have a clearer idea than me? I think if you make a simple test you
would encounter the same behaviour!



From: s.horne at packetizer.com
To: unazona at hotmail.com; h323plus at lists.packetizer.com
Subject: RE: [h323plus] Video Resolution
Date: Sat, 16 Jan 2010 01:37:07 +1000

You cannot know what the remote will send when you call OpenVideoChannel for
the decoding side, that can only be done when you receive the first RTP
You need to do a level 6 trace to work out who and why the channel is being
closed. I don't think it is a capability issue, usually the problem comes
from either the video encoder device (webcam) or the display device. Check
to see that you have set the video input device to send at the same size as
your encoder. The old openH323 used to do be able to do that automatically
as the frame size for the capability was known. You have to make sure the
input to the encoder from the webcam is correct.  
Version of h323plus would be irrelevent in this case. 


From: Carlos Haj [mailto:unazona at hotmail.com] 
Sent: Saturday, 16 January 2010 1:06 AM
To: s.horne at spranto.com.au; s.horne at packetizer.com;
h323plus at lists.packetizer.com
Subject: RE: [h323plus] Video Resolution


Thanks for valuable information. What is happening literally in a minimised
case: I derived OnVideoChannel

on the Local endpoint

if (encoding)
      codec.SetFrameSize(352, 288);
      cout << codec.GetWidth();
      cout << codec.GetHeight();
      // I receive CIF (ERROR)

on the Remote endpoint

if (encoding)
      codec.SetFrameSize(176, 144);
      cout << codec.GetWidth();
      cout << codec.GetHeight();
      // I receive CIF (normal)

I looked into H323 trace Log, (remote endpoint which supposed to send QCIF) 

PLUGIN       Error encoding frame from plugin H.261-CIF
H245          Request CloseLogicalChannel
H323RTP     Transmit H.261-CIF thread ended

It seems that the H.261 channel is closed prematurely. As my local endpoint
received an incorrect video size I suppose that local endpoint causes remote
to close the transmission channel.

Could this be related to the version of the plugin or h323plus lib which I
use? it's likely that the video resolution is sent before codec.SetFrameSize
is invoked!

Did you in practice used different video resolution under the same
capability? e.g. CIF<->QCIF calls



From: s.horne at spranto.com.au
To: unazona at hotmail.com; s.horne at packetizer.com;
h323plus at lists.packetizer.com
Subject: RE: [h323plus] Video Resolution
Date: Fri, 15 Jan 2010 23:14:23 +1000

The current behaviour is correct. 
The old OpenH323 used to only send CIF with *-CIF{sw} capability and only
QCIF with *-QCIF{sw} . This was changed with the video plugins so the
capability could do up to CIF so it would also supported QCIF. This is
perfectly H.245 legal.
In this way only 1 capability can do both frame sizes. This is the way most
manufacturers implement the capability exchange.  
The capability has a flag for the size it supports so the old CIF capability
used to say QCIF - 0 CIF - 1. So if you wanted to do QCIF you had to use the
*-QCIF{sw} capability as the QCIF flag in the *-CIF{sw} was 0. This was
changed so that the *-CIF{sw} capability had the QCIF flag so it could also
support QCIF. Then it was safe to remove the *-QCIF{sw} capability and only
exchange using the *-CIF{sw}. 
Now SetVideoFrameSize() will set the global frame size limit so regardless
of the direction that will be the maximum size permitted (if CIF only up to
CIF capability is available). The codec.FrameSize() in the
MyH323Endpoint::OpenVideoChannel() allows the implementor to set the actual
frame size to send. 
Is there something else I missed?


From: Carlos Haj [mailto:unazona at hotmail.com] 
Sent: Friday, 15 January 2010 8:39 PM
To: s.horne at packetizer.com; h323plus at lists.packetizer.com
Subject: RE: [h323plus] Video Resolution


Thanks for your quick answer, just noticed that I had a bad thread name;)

Well, I have the codec.SetFrameSize(w, h); in my OpenVideoChannel

When adding capabilities I use

AddAllCapabilities(0, P_MAX_INDEX, "*");

Capabilities table shows as 

Set 0: 0: audio
          1: H.261-CIF{sw}

I receive an OpenVideoChannel for encoder, I open channel and attach video
reader + colourConverter, just after that I receive a close video signal
from a H245Negotation, here I join Call Stack

>   testApp.exe!mmDDSVideoOutputBridge::close2()  Ligne 359    C++
     testApp.exe!mmVideoInputDevice::~mmVideoInputDevice()  Ligne 43 + 0x1b
     testApp.exe!mmVideoInputDevice::`scalar deleting destructor'()  + 0x2b
     testApp.exe!PVideoChannel::CloseVideoReader()  Ligne 203 + 0x24    C++
     testApp.exe!PVideoChannel::Close()  Ligne 145    C++
     testApp.exe!H323Codec::CloseRawDataChannel()  Ligne 488 + 0x11    C++
     testApp.exe!H323VideoCodec::Close()  Ligne 747    C++
     testApp.exe!H323Channel::CleanUpOnTermination()  Ligne 716    C++
     testApp.exe!H323_RTPChannel::CleanUpOnTermination()  Ligne 1160    C++
     testApp.exe!H245NegLogicalChannel::Release()  Ligne 1219    C++
H245_CloseLogicalChannelAck & __formal={...})  Ligne 1086    C++
H245_CloseLogicalChannelAck & pdu={...})  Ligne 1372 + 0xf    C++
     testApp.exe!H323Connection::OnH245Response(const H323ControlPDU &
pdu={...})  Ligne 3293 + 0x22    C++
     testApp.exe!H323Connection::HandleControlPDU(const H323ControlPDU &
pdu={...})  Ligne 3189 + 0x12    C++
     testApp.exe!H323Connection::HandleControlData(PPER_Stream & strm={...})
Ligne 3170 + 0x18    C++
readStatus=true, PPER_Stream & strm={...})  Ligne 3103 + 0x12    C++
     testApp.exe!H323Connection::HandleControlChannel()  Ligne 3085 + 0x13
     testApp.exe!H245TransportThread::Main()  Ligne 700    C++

If I remove the "SetVideoFrameSize(H323Capability::cifMPI);", I get the
following capabilities set

1: H.261-CIF{sw}

with exactly same strange behaviour, QCIF is not sending while CIF is being
received, by the way qcif endpoint says

Local Video Codec - H.261-CIF{sw}
Local Resolution - 176x144

Remote Video Codec - H.261-CIF{sw}
Remote Resolution - 352x288

I tried a "ReorderCapabilities(PStringArray("QCIF"));" after my
addcapabilities, I ended up with both endpoints using QCIF and ignoring my
SetFrameSize anyway!!

Is there a glitch using H323Plus video plugins? my code works perfectly on
openh323 stack.

"SetVideoFrameSize(H323Capability::cifMPI);" is supposed to define a maximum
video resolution?! as you said in API doc "... to set the maximum framesize
allowed to the specified value "

Is that usual to have H.261-CIF with a QCIF resolution? On which order codec
plugins can be added to avoid such problems of negotiation?



From: s.horne at packetizer.com
To: unazona at hotmail.com; h323plus at lists.packetizer.com
Subject: RE: [h323plus] Valid sessionID in OpenLogicalChannel command
Date: Fri, 15 Jan 2010 08:12:54 +1000

In your derived


From: h323plus-bounces at lists.packetizer.com
[mailto:h323plus-bounces at lists.packetizer.com] On Behalf Of Carlos Haj
Sent: Friday, 15 January 2010 12:59 AM
To: h323plus at lists.packetizer.com
Subject: Re: [h323plus] Valid sessionID in OpenLogicalChannel command

Hello Guys,

I would like to have different frame sizes for two endpoints, first I tried
to play around with H323Endpoint::SetVideoFrameSize, but it seems that part
changes the maximum allowed size, which means that if I switch the
videoFrameSize to qCIF, I wouldn't be able to receive CIF from the other
endpoint. my test only received QCIF.

I tried also to modify the OpalMediaFormat by using a GetWritableMediaFormat
for a capability, that ended with unusual CIF format while having a QCIF

On the other hand, I looked Opal examples where they use an OpalManager, but
unfortuntly that seems incompatible with h323plus, while old openh323
tutorials and exampls don't have any video plugins support.

How I can manage to receive and send different resolutions (frame sizes)
using H323plus?

I appreciate a lot your help



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