According to this article, Sony has decided to release its initial Blu-Ray (high definition) discs using the same MPEG-2 compression that today’s DVDs use, even though the Blu-Ray specification requires all compatible players to support both MPEG-4 AVC and SMPTE VC-1 (Microsoft’s WMV9 HD) formats. Sony’s argument is that MPEG-2 encoders are used by every DVD authoring system on the planet, while AVC and VC-1 encoders are still both rare and expensive. The capacity of Blu-Ray discs (25-50GB) is more than sufficient to store a full-length HD movie in MPEG-2, so Sony will stick with MPEG-2 until they need to use one of the more space-efficient alternatives.
Sony’s move has come as a surprise to most of its partners in the Blu-Ray consortium, not to mention the DVD authoring houses that are gearing up to support Blu-Ray. If MPEG-2 is more than sufficient for the task, why did Sony bother to include AVC and VC-1 in the Blu-Ray standard in the first place? AVC and VC-1 will add cost and complexity to every Blu-Ray player made; without those codecs, players will be considerably less expensive.
One possible outcome of Sony’s decision is that it might actually reopen the door for HD discs based on red-laser DVD technology. If Sony is saying that it doesn’t think that consumers really want or need all the special features that would be possible using a next-generation codec, why can’t AVC- or VC-1-compressed HD films be put onto conventional DVDs? After all, that’s what Microsoft has been doing for two years now with its WMV HD DVDs. In addition, it neutralizes the capacity advantage that Blu-Ray has over HD DVD, which will also support both AVC and VC-1. Encode in a next-generation format for HD DVD, and get all the special features, or encode in MPEG-2 for Blu-Ray and be stuck with the same amount of special features as today’s DVDs.
I suspect that Sony’s move was designed to eliminate one source of technical risk from Blu-Ray’s launch, but it sends a mixed and confusing message to Sony’s partners and the market in general. If MPEG-2 is “good enough,” then maybe the DVDs that we all know and love, with the right codecs, are good enough as well.