Polycom V500 Release Note page 22

Release Notes
V500 and VSX systems, version 8.5
Feature Limitation
Interoperability H.320 calls to an MGC continuous presence, H.329 IVR
MGC conference transmit H.263 video instead of H.264.
H.320 conferences with MGC configured for Pro-Motion
connect in secondary (audio-only) mode. To work around this
issue, call using H.323 or configure the MGC to not use
Pro-Motion.
Some ISDN endpoints may fail to connect when blast-dialing
from MGC. Redial any sites that fail to connect manually.
In MGC H.239 conferences with G.711 forced, the VSX 8000
may reboot.
When the MGC dials out to the VSX system in H.323
Pro-Motion, it connects H.263 (no annexes) at 30 fps. This is
due to a difference in the way the MGC and VSX system set
rates in their video caps and how they use the caps to
determine the call rate. The result is that a 768 kbps call
looks to the VSX system like a 704 kbps call, so Pro-Motion
is not selected as the transmit video mode. The workaround
for this is to set the VSX system to do Pro-Motion at 512 kbps
and above.
When a VSX system joins an encrypted
People+Content/H.239 continuous presence MGC multipoint
call, the VSX system does not support far end camera
control.
Interoperability V500 and VSX systems can make but not receive calls when
Microsoft behind a Microsoft MN-500 UPnP device.
In a Live Communication Server (LCS) environment, an
endpoint that places a SIP call into a multipoint conference
hosted by a VSX system and subsequently hangs up may
appear to still be in the conference, with no audio and frozen
video. If this occurs, hang up the site from the host VSX
system to restore normal operation.
Interoperability In calls with ViewStation 128 systems, Far End Camera
Polycom Control might not work for the first 3 minutes or so.
ViewStation 128
Interoperability When a VSX system places a H.320 to H.323 gateway call
RADVISION through a RADVISION viaIP gateway, it cannot send or
receive H.239 content.
Calls between H.323 VSX 8000 systems and H.320 iPower
9000 systems made through a RADVISION viaIP gateway
may cause the iPower system to restart on hang-up.
Interoperability VSX 8000 systems with a Sony BRC300 camera may not
Sony correctly move to camera presets.
In H.320 calls where a VSX system is MCU, systems may
not receive content.
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