Cisco Unified MeetingPlace Release 8.5 -- Choosing Between the Hardware Media Server and the Express Media Server
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Contents |
Choosing Between the Hardware Media Server and the Express Media Server
- About the Hardware Media Server and the Express Media Server
- General Differences
- Differences in Audio and Video Codecs
- Line Echo Cancellation
About the Hardware Media Server and the Express Media Server
All Cisco Unified MeetingPlace Release 8.5 systems that will use audio or video need a media server and the media server can be either a Hardware Media Server (HMS) or an Express Media Server (EMS).
- The Express Media Server is a set of software modules, including an audio mixer and a video switcher, that resides on the Application Server. The Express Media Server creates a single box software-only solution for Cisco Unified MeetingPlace. The Express Media Server is based on the Cisco Unified MeetingPlace Express Video Telephony (VT) product.
- The Hardware Media Server is comprised of Audio and Video Blades.
All Cisco Unified MeetingPlace Release 8.5 systems automatically come with an Express Media Server. If you want to use a Hardware Media Server, you must purchase, install, and configure it first.
On a multinode system (with Cisco WebEx scheduling), you may use only the Express Media Server or the Hardware Media Server within a site. If you mix both EMS and HMS on the same site, then users may notice video quality differences for different meetings, depending on the media server that is being used. On a multinode system, one site can have the Express Media Server, while another site has the Hardware Media Server.
There can be more or less differences based on your configuration and the environment in which the media servers are deployed.
General Differences
Table: General Differences Between the Express Media Server and the Hardware Media Server
Feature | Express Media Server | Hardware Media Server |
---|---|---|
Type |
Software residing on the Application Server |
Hardware, comprised of Audio and Video Blades. For video to work, each Audio Blade must have a Video Blade associated with it. |
Installation |
Installed automatically when you install the Application Server |
Separate chassis, audio/video blade installation required and configuration steps |
Configuration |
Configured through the Administration Center of the Application Server |
Configured through the Media Server Administration |
Recording |
Can record the audio portion of scheduled meetings. Cannot record the video portion of scheduled meetings.
|
Can record the audio and video portions of scheduled meetings. |
Cascading |
Does not support any internal cascading of audio and video data |
Uses internal cascading for scalability |
Resource management |
Based on the number of System Resource Units (SRUs), which is based on the type of Cisco MCS on which the Application Server is installed.
|
Based on the following:
|
High complexity codecs |
G.729 is considered a high complexity codec |
G.729 is not considered a high complexity codec unless line echo cancellation is turned on for it. |
Video composition |
Not supported.
|
Supports video composition.
|
Muting |
When audio is muted, video is not muted. |
When audio is muted, video is muted. |
Transrating |
Not supported.
|
Supports true transrating, so you can have an ISDN connection in the same meeting as a 2Mb connection, without affecting the interaction between high rate participants. |
Transcoding between H.263 and H.264 AVC |
Not supported between H.263 and H.264 AVC endpoints in the same meeting. A meeting can include either H.263 or H.264 video endpoints. |
Supported. |
H.261 |
Not supported. |
Supports H.261 in high rate mode and provides transcoding between H.261 and H.263/H.264. |
Video resolution |
Supports the following:
|
Allows 320x180, but it will probably be mangled. Does not allow the other resolutions.
|
Custom video types |
Can make custom video types. Has more predefined video types. |
Not supported. |
Video type management |
Supported.
|
Not supported.
|
H.263 at 4CIF |
Not supported. |
Supported. |
In-band (voice band) DTMF detection, audio codec iLBC, jitter buffer configuration |
Not supported. |
Supported. |
Automatic gain control (AGC) |
Supported. |
Supported. |
Echo cancellation |
Supported. |
Supported. |
The system calls a user for a web meeting, and the user turns on the desktop camera. When the user is speaking, the WebEx video shows the user to the other attendees in the meeting. |
Supported. |
Not supported. |
Differences in Audio and Video Codecs
Audio Codecs Supported | Video Codecs Supported | |
---|---|---|
Hardware Media Server |
|
|
Express Media Server |
|
|
1. When using these codecs, capacity changes from 250 ports per blade to 166 ports per blade.
2. Any combination in the same meeting.
3. For more information on using these codecs and capacity, see the Resource Management and System Capacity for Systems Using the Express Media Server.
Line Echo Cancellation
The Express Media Server and Hardware Media Server both include an echo canceller for controlling echo on incoming audio connections, so any echo originating from a phone or long distance connection can disrupt the conference. In general, echo cancellation is not required in a conference bridge, providing the following conditions are true:
- All the voice gateways connecting the public switched telephone network to the internal network are provisioned to provide echo cancellation. Usually 64ms of echo cancellation is sufficient, but intercontinental calls may benefit from 128ms.
- Substantially all calls are originating and terminating within the same continent. If you have 128ms of echo cancellation in the voice gateways, then intercontinental calls between developed countries will likely be covered, provided no connections through satellites are employed. Intercontinental calls involving 3rd world countries are likely to have echo exceeding 128ms., which cannot be controlled by most voice gateways.
- Internal phones and headsets are well maintained. Defective phones or headsets, including echo cancelling headsets with dead batteries, are a common source of echo.
Note that acoustic echo, typically from a speakerphone in a conference room, cannot be effectively cancelled by either type of media server. This type of echo should be controllable through proper configuration and use of a good quality speaker phone.