Polycom negotiate to G.728 on non G.728 machine

[imcans]

The VSX7000 and V500 endpoints from Polycom always negotiate to send G.728 audio to non G.728 machine like Leadtek 8750 or Leadtek 8770. This will not allow the users from Leadtek side to communicate with the other side since they will get only the noise on the conference.

Does anyone know how to force VSX7000 or V500 to use G711 or G.723.1 which is used by Leadtek endpoint?

Thanks
Pak
IMCANS

[tom9933]

I placed a few test calls with a V500 and a VSX7000 and captured the audio portion of the caps exchange that appears below.
Audio Simultaneous[0]:
Siren 48K: frames=1, maxBitRate=48
Crypto: AES-CBC
Siren 32K: frames=1, maxBitRate=32
Crypto: AES-CBC
Siren 24K: frames=1, maxBitRate=24
Crypto: AES-CBC
G7221 32K: frames=1, maxBitRate=32
Crypto: AES-CBC
G7221 24K: frames=1, maxBitRate=24
Crypto: AES-CBC
G7221 16K: frames=1, maxBitRate=16
Crypto: AES-CBC
G722: frames=20, maxBitRate=64
Crypto: AES-CBC
G728: frames=8, maxBitRate=16
Crypto: AES-CBC
G711U: frames=20, maxBitRate=64
Crypto: AES-CBC
G711A: frames=20, maxBitRate=64
Crypto: AES-CBC
G729A: frames=2, maxBitRate=8
Crypto: AES-CBC
Siren Stereo 48K: frames=1, maxBitRate=48
Crypto: AES-CBC
Siren Stereo 56K: frames=1, maxBitRate=56
Crypto: AES-CBC
Siren Stereo 64K: frames=1, maxBitRate=64
Crypto: AES-CBC
Siren Stereo 96K: frames=1, maxBitRate=96
Crypto: AES-CBC
What appears to be your problem is that the Polycom doesn’t show support for G723.1 so it appears to be negotiating G728 instead. The odd thing here is that the Polycom shouldn’t use G728 unless the Leadtek is also advertising it. I would suggest telneting into both units and getting a trace that can be sent to support.
On the work around side I have two suggestions:
1) Try the call at a higher rate. The reason for this is that G728 is typically preferred in lower speed calls i.e. 192k and below. By increasing the call rate you might get the systems to negotiate G711 or G722 instead.
2) Try putting both endpoints into a conference on an mcu.
Good Luck,

[Sean Lessman]

The VSX7000 and V500 endpoints from Polycom always negotiate to send G.728 audio to non G.728 machine like Leadtek 8750 or Leadtek 8770. This will not allow the users from Leadtek side to communicate with the other side since they will get only the noise on the conference.

Does anyone know how to force VSX7000 or V500 to use G711 or G.723.1 which is used by Leadtek endpoint?

Thanks
Pak
IMCANS
If the Leadtek does not present decoding capabilities for G.728, then the Polycom should not encode and transmit it. If the capability is not presented, then its a Polycom bug. If it is presented, then its perfectly legitimate for Polycom to encode it.

Sean

[asoussa]

I placed a few test calls with a V500 and a VSX7000 and captured the audio portion of the caps exchange that appears below.
Audio Simultaneous[0]:
Siren 48K: frames=1, maxBitRate=48
Crypto: AES-CBC
Siren 32K: frames=1, maxBitRate=32
Crypto: AES-CBC
Siren 24K: frames=1, maxBitRate=24
Crypto: AES-CBC
G7221 32K: frames=1, maxBitRate=32
Crypto: AES-CBC
G7221 24K: frames=1, maxBitRate=24
Crypto: AES-CBC
G7221 16K: frames=1, maxBitRate=16
Crypto: AES-CBC
G722: frames=20, maxBitRate=64
Crypto: AES-CBC
G728: frames=8, maxBitRate=16
Crypto: AES-CBC
G711U: frames=20, maxBitRate=64
Crypto: AES-CBC
G711A: frames=20, maxBitRate=64
Crypto: AES-CBC
G729A: frames=2, maxBitRate=8
Crypto: AES-CBC
Siren Stereo 48K: frames=1, maxBitRate=48
Crypto: AES-CBC
Siren Stereo 56K: frames=1, maxBitRate=56
Crypto: AES-CBC
Siren Stereo 64K: frames=1, maxBitRate=64
Crypto: AES-CBC
Siren Stereo 96K: frames=1, maxBitRate=96
Crypto: AES-CBC
What appears to be your problem is that the Polycom doesn’t show support for G723.1 so it appears to be negotiating G728 instead. The odd thing here is that the Polycom shouldn’t use G728 unless the Leadtek is also advertising it. I would suggest telneting into both units and getting a trace that can be sent to support.
On the work around side I have two suggestions:
1) Try the call at a higher rate. The reason for this is that G728 is typically preferred in lower speed calls i.e. 192k and below. By increasing the call rate you might get the systems to negotiate G711 or G722 instead.
2) Try putting both endpoints into a conference on an mcu.
Good Luck,


Let me know how can you capture the CAPS during a video call, is there a certain software?

[tom9933]

On a Polycom endpoint it’s as simple as opening a telnet connection using a program like HyperTerminal. To capture a trace with the caps exchange, do the following:
1) Connect to the unit with a telnet program
2) Turn on capture in the telnet software
3) Place a call
4) Turn off capture
5) Disconnect the call and the telnet session
6) Look through the capture file with a text editor until you find the caps exchange section.

NOTE: Some endpoints will modify their caps exchange based on the far site so when capturing the caps exchange make sure you call a few different endpoints. Generally manufacturers will do this to maintain legacy support since the older systems tend to get upset when they see the newer standards.