As mentioned elsewhere in this toolkit, the use of the term “standards-based” and “consumer-grade” to define the different videoconferencing markets may result in some concerns or confusion. After all, some consumer-grade products use standards for video encoding, while other standards-based systems may not implement all of the possible videoconferencing standards.
Below is a collection of many of the standards that are pertinent to videoconferencing, with the caveat that they focus on IP-based, packet-switched networks and products as opposed to ISDN-based or telephony-based systems. You will find a description of the standards, as well as a list of which manufacturers support them.
Multimedia Call Control Standards – SIP and H.323
These two standards help initiate, manage, and terminate audio-video communications on networks. SIP and H.323 do not communicate between one another, although interoperability can be established with a gateway device, which helps translate between the two protocols. A standard included within the H.323 standard is H.245, which serves as the primary call control “handshake” that occurs between devices at the start of a videoconferencing session. The H.245 standard has been updated to include a faster call control protocol based on the H.255 standard, supporting something called the “Fast Connect” procedure.
Manufacturers’ products that support SIP:
- Apple iChat
- Cisco/Tandberg Movi
- LifeSize Desktop
- Polycom CMA
- Polycom PVX
- Skype
- Vidyo Desktop
Manufacturers’ products that support H.323:
- Cisco/Tandber Movi
- Polycom CMA
- Polycom PVX
- Vidyo Desktop
Video Standards – H.263 and H.264
These two standards are used to compress video, specifically in this context to reduce bandwidth when sending video data over a network between two video systems. H.264 provides significant improvements in compression over H.263 and older H.26X standards. H.264 is also referred to as H.264/AVC for “Advanced Video Coding,” or Single-Layer H.264.
The following manufacturers’ products support the H.263 standard:
- Cisco/Tandberg Movi
- LifeSize Desktop
- Polycom CMA
- Polycom PVX
- Vidyo Desktop
The following manufacturers’ products support the H.264 standard:
- Apple iChat
- Cisco/Tandberg Movi
- LifeSize Desktop
- Polycom CMA
- Polycom PVX
- Vidyo Desktop
A series of amendments (referred to as “annexes”) have been added to the H.264 standard. One of the actively discussed additions to the standard is Annex G, which discusses the standard for Scalable Video Coding (SVC). This standard can improve apparent video quality when handling traffic over networks with high packet loss or jitter, but requires a gateway device to transcode to devices that do not support it.
The following manufacturer’s product uses H.264 Annex G
- Vidyo Desktop
Video Standards – Other
Consumer-grade desktop videoconferencing systems typically use closed-source or proprietary codecs for handling video compression and encoding. An example of these standards include the On2/VP8 codec that was created by Google and is licensed for use by Oovoo and Skype.
Audio Standards – G.711, G.722, G.729
These standards are used for companding audio in video conferencing. G.711 is the standard required by H.323, whereas G.722 and G.729 are optional. The primary difference between these standards is the sampling frequency and compression of the audio. G.722 provides improvements by doubling the sampling frequency of the audio when compared to G.711, which results in a potential improvement in the quality and clarity of the received audio, but an increase in the required bandwidth.
G.729 requires less bandwidth by providing a less literally accurate transmission of sound that has been optimized for speech. This may make speech sound clearer, but less true to the actual voice data (and likely to be non-ideal for medical diagnosis, such as electronic stethoscopy).
As with the video standards, various annexes exist define additional functionality on top of the original standard.
The following manufacturers’ products support G.711:
- Cisco/Tandberg Movi
- LifeSize Desktop
- Polycom CMA
- Polycom PVX
- Skype
- Vidyo Desktop
The following manufacturers’ products support G.722:
- Cisco/Tandberg Movi
- LifeSize Desktop
- Polycom CMA
- Polycom PVX
- Vidyo Desktop
The following manufacturers’ products support G.729:
- Cisco/Tandberg Movi
- LifeSize Desktop
- Polycom CMA
- Polycom PVX
- Vidyo Desktop
Audio Standards – Other
Skype has created an additional audio codec that it sometimes used, called SILK. This codec is proprietary, but can be used by other manufacturers and entities through a royalty-free license. iLBC, or Internet Low-Bandwidth Codec is another standard, this one a royalty-free codec developed by Global IP Solutions, that is used by some manufacturers.
Content Sharing Standard – H.239
This standard arose out of the desire to stream an additional video channel over an H.323 multimedia call. It allows for a feature often referred to as “screen sharing,” wherein a user can send a video image of their computer desktop and applications to another user, with the content appearing on a secondary monitor or in a Picture-in-Picture layout.
Manufacturers’ products that support H.239:
- Cisco/Tandberg Movi
- Polycom CMA
- Polycom PVX
- Vidyo Desktop
Security – AES, TLS
Advanced Encryption Standard (AES), and Transport Layer Security (TLS) are standards that provide encryption when engaging in conference calls, rendering signaling, data transfer, video and audio information secure to those who might try to intercept a video conference that is in session. It is important to note the separation between those four areas (signaling, data, video, audio), as some software may only encrypt video, audio, and data, while leaving call signaling unencrypted. The term HTTPS refers to the TLS protocol used with HTTP, creating HTTP traffic that is secure.
Manufacturers’ products using AES and/or TLS:
- Apple iChat – requires a .Mac account
- Cisco/Tandberg Movi
- LifeSize Desktop
- Polycom CMA
- Polycom PVX
- Skype
- Vidyo Desktop
Firewall and NAT Traversal Standards – H.460, STUN, TURN, ICE
NAT, or Network Address Translations, are where multiple IP addresses in a network are “hidden” behind a single public-facing IP address. This process can make it difficult for two devices in different networks to communicate, as they will see all communication as coming from the single, public-facing IP address. A way to think about this is to consider an apartment complex; the building will have one street number, and within that building there are many individual unit numbers.
NAT and firewall traversal helps to overcome the problem of non-public IP addresses. There are several standards that are used, and manufacturers may use one or many of these techniques to communicate through a firewall or to a “NATed” address.