Codec frees video telephony
A new royalty-free video codec looks set to deliver reliable broadcast-quality video communications to relatively low-spec PCs and mobile phones, writes Bill Pechey
Bill Pechey, IT Week, IT Week 04 Apr 2003
The International Telecommunication Union (ITU) and the International Organisation for Standardisation (ISO) are currently creating a new video codec that could be the catalyst for mainstream use of video telephony by businesses and consumers.
The project is being developed by the Joint Video Team (JVT) and has proved a great success, with standardisation work now almost complete. The result will be known by the prosaic name of H.264.
The performance of the new H.264 codec is remarkable; it only needs about half the bit rate of the previous best codecs, H.263 and MPEG4, and about a quarter of that needed by MPEG2, which is used in digital TV.
This means that video conferencing systems will be able to operate on low-bandwidth channels such as GPRS and dial-up modems, and up to four times as many video channels could be transmitted on digital TV systems using the current bandwidth.
Trial implementations and system tests have begun in earnest. Canadian company UB Video has demonstrated a broadcast-quality codec running on a single Texas Instruments TMS320C64x DSP chip, and the Heinrich Hertz Institute in Berlin has shown that a 1.8GHz PC can decode high-definition TV in very close to real time.
Perhaps the most impressive demonstration was given by BT's research labs when it showed an H.264 decoder running on a Nokia 7650 mobile phone.
BT's implementation uses Quarter Common Intermediate Format (QCIF), which offers a resolution of 176x144 pixels, and can decode at about 14 frames per second.
The video bit rate was about 20kbit/s, which can be handled by either GPRS or HSCSD mobile data technology. It will be interesting to see how much BT can optimise its decoder, and whether we need to wait for the next generation of mobiles before we can have the standard 25 frames per second.
One of the initial goals of the H.264 project was that the so-called "baseline" codec should be free of problems with patents. It should be possible to build products using the technology without having to pay royalties. I originally laughed at this idea and talked about flying pigs, but it appears that the aim has come true; the baseline codec uses technology that is either not patented or the patent holders have waived their rights to royalties.
Though the baseline specification is not as good as the more advanced add-on options, it is still a lot better than any previous codec. Achieving a royalty-free baseline is probably more important than the excellent technology. The implementation of H.263 and MPEG4 has been hindered by patents; H.264 should get off to a roaring start without this baggage.
We should see H.264 appearing in many places. I think that video-telephony terminals will be the first application, closely followed by advanced mobile phones. BT's implementation runs on the Symbian operating system of the 7650 so it should be easy to port to other Symbian-based mobiles.
It will be some time before H.264 is used for broadcasting because it is unlikely that set-top boxes can be upgraded to support the new decoder. However, the benefits are so substantial that ways will eventually be found.
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