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Choosing Video Standards that Work

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September 24, 2008

Choosing Video Standards that Work

By Brough Turner, Brough Turner is Chief Strategy Officer of Dialogic.


Truly successful and widely adopted mobile services not only deliver what customers want, but also work on any network with any handset. Economists call this the network effect. Networking folks call it Metcalf’s law: “the value of a network increases as the square of the number of users”. The more people you can interact with the better, and that’s where standards come in. Of course, the difficulty with standards is there are so many of them! In the end, the standards that count are those that get widely deployed.

 
Mobile video is a case in point. There are many different mobile video applications, from mobile broadcast TV, to viewing video clips, to creating video clips, to live “see-what-I-see,” to full two-way video telephony. For each of these application areas there are one or more targeted video standards, but successful applications also leverage widely deployed standards whether they are an ideal match or not.
 
Video Telephony
 
The first, and for a long time, the only widely deployed mobile video standard was 3G-324M. This is a standard for two-way live video telephony. In the 1990s, as mobile networking folks considered 3G, many were captivated by the idea that two-way video telephony would be the killer application for the new networks. And from the beginning of 3GSM (News - Alert) service (by DoCoMo in Japan in 2001), great efforts were made to ensure that all terminals with video capability supported at least a baseline version of the 3G-324M.
 
Since 3G-324M was designed for two-way live video telephony, it was designed for low latency, and since it rolled out with the first 3G networks, it had to work with the limited bandwidth of those networks. The solution was to use 64 Kbps circuit-switched data connections and adapt the ITU video standards for low bit-rate video telephony; i.e., H.324. The resulting system is limited to QCIF resolution (176 x 144) but video call setup is almost as fast as voice call setup and the service is highly interactive with less than 1.5 seconds screen delay when video streams are switched.
 
Besides its early start, a major reason many applications leverage 3G-324M standards today is that they work on all 3GSM networks (except in the U.S.) and are supported on roughly 80 percent of all 3GSM handsets (again, outside the U.S.).
 
Multi Media Messaging Service (MMS)
 
MMS is also widely supported on 3G handsets although with handset-to-handset variations, network-to-network problems in some countries and file size restrictions that limit the resolution, frame rate and/or duration of a video clip. MMS standards are set by the 3GPP and all video MMS-enabled handsets are required to support at least H.263 profile 0, level 10 encoding and 3GPP file format (.3gp). In practice this yields handsets that support QCIF (176 x 144 pixels) and sub-QCIF resolutions (e.g. 128 x 96).
 
Beyond the baseline, many handsets support other coders, other file formats and higher resolutions, but these capabilities are typically for the playback of content from a server rather than person-to-person messaging, as person-to-person requires a minimum common format. Adoption of videoMMS has been slow in many markets. Where video MMS is widely adopted (in parts of the EU for example), service usage only rose after a substantial number of video-enabled handsets had been sold and popular MMS-specific applications were launched, for example, See Me TV which launched in the UK in 2005.
 
Streaming Video Playback (over 3G IP Data)
 
Most video-capable handsets also support streaming video playback, however handset capabilities vary widely. Eventually all handsets should support 3GPP’s Packet Streaming Service (PSS) — a form of RTSP — however PSS standards are fairly new. For now many handsets support 3GPP streaming over RTP and the RealAudio/RealVideo streaming formats from Real Networks.
 
Widely varying handset capabilities put an extra burden on application providers to identify each customer’s handset and provide the best quality possible on that handset.
 
3G Video Sharing (on IMS)
 
Real world experience with two-way mobile video telephony shows most people don’t use the service as intended. Instead they use it to support one-way, “see-what-I-see” video during a two-way audio conversation.
 
To support see-what-I-see, Nokia (News - Alert) launched and then 3GPP standardized, streaming video over IP under 3GPP’s IMS standards. It’s called 3G video sharing and it uses SIP and IMS to set up a one-way video stream, directly or in combination with an existing voice call. Once again, the minimum required encoding is H.263 profile 0, level 10. Newer handsets can do better than this, but person-to-person communications uses whatever both ends are capable of supporting. Capabilities negotiation is by exchange of session description protocol (SDP) data in SIP packets during call setup.
 
Video Sharing standards are relatively new and efforts to produce baseline interoperability test scenarios only began in October 2007. Since a person-to-person communication service requires widely deployed, interoperable devices, it’s likely to be a few years before 3G video sharing is widely used. Indeed, AT&T (News - Alert) Wireless launched a video sharing service in the US in 2007 but you can only call other AT&T customers who have one of the four supported handsets. As a result, service adoption has been very slow — for now, it’s mostly a cool demo.
 
Mobile TV
 
The final area of mobile video standards is mobile TV. Here most of the talk is about new broadcast networks, but most current deployments are based on unicast streaming over the existing two-way cellular network using mobile video streaming as discussed above. There is also some ambiguity as the term mobile TV is used for both stored video clips (from TV or otherwise) and live broadcast TV.
 
Mobile TV based on new broadcast networks is developing slowly as it requires new frequencies, new base stations and new handsets. The first such service launched in Korea in 2005 (see DMB below). However the second service, launched by Hong Kong CSL in March 2006, bypassed new network technology and instead broadcasts live TV channels over existing 3G networks using the 3G-324M video telephony capability available on all networks and nearly all 3G handsets in Hong Kong.
 
Going forward, the contending standards for new mobile broadcast networks include:
 
• Digital Multimedia Broadcasting (DMB) as used in Korea since 2005. There are two flavors — a satellite version (DMB-S) and a terrestrial version (DMB-T).
• Integrated Services Digital Broadcasting-Terrestrial (ISDB-T). An adaptation of this service (called 1Seg) has been in use for mobile TV in Japan since early 2006.
• Digital Video Broadcasting-Handheld (DVB-H) is the Europe Union’s preferred approach, launched in several EU countries since mid-2006, and more recently in India and elsewhere in Asia.
• MediaFLO is a system created by Qualcomm with services launched in the U.S. this year by Verizon (News - Alert) and then AT&T.
 
Another contender is Multimedia Broadcast Multicast Service (MBMS). MBMS does multicasting over existing GSM and UMTS cellular networks. This avoids the expense of new spectrum and new base stations although it will still require customers to purchase new handsets. Various MBMS systems have been trialed and deployments are expected later this year. As MBMS is just an extra operating mode for normal 3G UMTS cellular networks, it’s likely to become widespread over time. Indeed, MBMS may win in the end.
 
What Works Today?
 
For mobile application developers, the critical issue is to make an application that “just works” with the maximum number of handsets possible. That typically means supporting 3G-324M video (except in the US), MMS, video clips attached to email and multiple video-over-IP formats. For interactive functions, 3G-324M is particularly well-suited since video stream switching takes less than 1.5 seconds and facilities are readily available to overlay image, banners and text menus on top of video. On the other hand, 3G-324M is limited to QCIF resolution (176 x 144 pixels) while many new handsets will support QVGA (320 x 240) or higher resolutions like WQVGA (480 x 272).
 
If the application includes user-generated video, it’s important to support multiple methods of video uploads including MMS, email and 3G-324M. MMS can be easy to use (although this depends on the specific handset vendor’s user interface) but MMS is frequently limited in size and thus in the length of the video clip as well as its resolution and frame rate. Where mobile email is available, it usually allows for larger attachments. Finally 3G-324M allows continuous streaming and therefore supports videos of any length as well as live broadcasting — your mobile phone truly becomes a portable webcam.
 
Mobile handsets are more diverse than personal computers, mobile networks more special purpose than the Internet and mobile video standards less mature than video on the Internet. On the other hand it’s a safe bet that, in the next few years, everyone will be carrying a portable webcam — their mobile phone. That’s a lot of webcams which will enable a lot of new applications!
 

Brough Turner, co-founder and CTO of NMS Communications, writes the Next Wave Redux (News - Alert) column for TMCnet. To read more of Brough´┐Żs articles, please visit his columnist page.

Edited by Stefania Viscusi







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