VC-1 standard finally arrives

SAN JOSE — After two years of suspense worthy of a Hitchcock movie, the Society of Motion Picture and Television Engineers (SMPTE) has released complete specifications for the VC-1 video compression standard.

The completion of the VC-1 standard arrived two years after originally promised by Microsoft Corp., which has been eager to turn its proprietary Windows Media Video 9 into an industry standard.

VC-1 documents including "VC-1 Compress Video Bitstream Format and Decoding Process"– the standard itself– and two supporting recommended practices can be purchased on the SMPTE website .

Asked about their own VC-1 implementations, several speakers at the Embedded Systems Conference here this week said they are for now depending on Windows Media Video 9 (WMV9), Microsoft’s implementation of VC-1, to bring it to the market.

Ajit Rao, group manager for multimedia codecs at Texas Instruments, said that WMV9 is "identical" with VC-1. But he added that the two "may drift in the future."

While Microsoft is making sure that WMV9 decodes VC-1 syntax correctly, the software giant may add new tools and improve future versions of WMV, Rao explained.

Interoperability of VC-1, however, is a concern for both encoder and decoder vendors.

According to SMPTE, its Compression Technology Committee has formed a new Working Group dedicated to providing maintenance of the test materials and documents, as well as the administration of a bitstream exchange program.

In theory, if everyone in the industry used Microsoft’s implementation of VC-1, interoperability between different encoders and decoders could be insured. But, in reality, every encoder vendor, reading SMPTE documents, can approach VC-1 encoding problems with a different strategy.

In other words, even if "the syntax one encoder emits must adhere to the standard, the code values stuffed into different elements of the syntax can be radically different," according to an industry expert who spoke on the condition of anonymity. The industry cannot be sure of interoperability unless it carries out "an industry-wide bitstream exchange program between different encoder manufacturers and different decoder manufacturers," he added.

Indeed, TI’s Rao, while outlining a number of compression tools available for different video codecs at the conference here, stressed that although compression standards specify the required syntax, "it’s your choice" to make algorithmic decisions for codec implementation.

Nonetheless, VC-1-- with or without industry-wide interoperability testing-- is positioning itself for deeper inroads in the consumer electronics market.

HD DVD and Blu-ray, the next-generation optical media specifications, have chosen VC-1 as one of three formats studios can use to deliver their movies in high definition. Warner Bros. Studios announced they will use VC-1 when they release titles in HD DVD.

Modeo, a mobile TV company based in Houston, will broadcast mobile TV to cell phones, portable media players and laptop computers by using Microsoft’s WMV9.

The consumer electronics industry today is being bombarded with new video compression technologies-- namely H.264, VC-1 and China’s AVS1.0.

TI's Rao, in comparing VC-1 and AVS1.0 with H.264, said that "VC-1 achieves a compression ratio similar to H.264 but at lower complexity." In contrast, China’s AVS1.0, while similarly reducing the complexity compared to H.264, "loses a little in compression efficiency," he added.

Rao said that when compared to the H.264 Main Profile, China’s AVS1.0 is "about 0.3 dB worse in average for progressive sequences" and "up to 1.2 dB worse for interlaced sequences." China, however, is currently defining a new profile in AVS1.0 to resolve such quality issues, he added.