The Blu-ray Disc Association has added the MPEG4 and VC1 video codecs to its specification for prerecorded Blu-ray Disc media, it said Wednesday. Blu-ray Disc is one of two formats vying to become the de facto optical disc standard for high-definition video.
As a result, the two codecs will form part of version 1.0 of the BD-ROM logical format, which is expected to be approved later this year, said Richard Doherty, Panasonic Hollywood Labs' managing director of Blu-ray and professional A/V (audio/visual), in a telephone interview on Wednesday. The logical format specifies the way in which content is stored on the disc. The physical format, which concerns technical specifications for the disc itself, was already approved in July this year.
VC1 is based on Microsoft's Windows Media 9 codec, and was previously called VC9, said Doherty. MPEG4.AVC is based on the H.264 codec.
The main advantage of adding the two codecs to the specification is an increase in the apparent capacity of the disc, said Doherty. This is because the newer codecs are more efficient at compressing data than the MPEG2 codec that's used with the rewritable Blu-ray Disc format and so allow more video to be stored in the same amount of space.
In the case of a 25G-byte single-layer Blu-ray Disc, about two hours of video encoded in MPEG 2 at a data rate of between 23M bps (bits per second) and 25M bps can be stored, Doherty said. MPEG2 is used in DVD Video and the first generation of the rewritable version of the Blu-ray Disc format. In contrast, the two new codecs can achieve an equivalent quality of video at about half the data rate and so expand the 25G-byte disc's capacity to up to 4 hours, he said.
"There are other advantages to having two compression techniques," Doherty said. "Moving forward, the technologies can have competition to help drive down licensing fees and improve picture quality."
HD-DVD (High Definition/High Density-DVD), the main competitor to Blu-ray Disc, has already made the two codecs part of its standard for prerecorded discs. In June companies supporting HD-DVD trumpeted this as one of its advantages over Blu-ray Disc.
"With this adoption, all that (advantage) is gone," said Doherty.
Adoption of the advanced codecs in future versions of the BD-RE rewritable format depends as much on technology as standardization talks, said Doherty. High-definition broadcasting in Japan and the U.S. uses the MPEG2 format, and current recorders put this broadcast data stream directly onto the disc. Using one of the two new codecs would mean real-time hardware transcoding, and that's too difficult to do in a consumer-level machine at present, he said.
Blu-ray Disc comes from a group of 13 companies led by Sony and also including Dell, Hewlett-Packard, Hitachi, LG Electronics, Matsushita Electric Industrial (Panasonic), Mitsubishi Electric, Philips Electronics, Pioneer Electronics, Samsung Electronics, Sharp, TDK and Thomson Multimedia.