HD-DVD And Blu-ray Disc
Dear Gary: I had some questions regarding HD DVD and Blu-ray Disc: 1) I would have to do some calculations, which I think several of us have done before, which tells us what the ideal average (sustained) bitrate would be for prerecorded media so that you would remain within the storage capabilities of a single-sided, dual-layer HD DVD disc. Is 30 GB storage for a single-sided, dual-layer HD DVD ROM disc correct? Unlike DVD, there is plenty of room to “adjust” the degree of compression for DVD, depending on the length of the feature film, desired extras, etc. With HD DVD, a small increase in compression can yield a lot more free space. With HD DVD utilizing [Microsoft] VC-9, they would first decide how much room is required for the soundtrack, extras, etc. then adjust the compression so that everything “fits.” Unlike current WMV HD (VC-9) discs which limit horizontal resolution to 1440 (1440 x 1080), HD DVD will be utilizing 1920 x 1080p. I would also like to know more about what the “ideal” (sustained average) compression rates are for VC-9 and H.264 for 1920 x 1080p with 30 GB of storage with HD DVD, I don’t see storage space as much of an issue anymore. I just hope that studios will release two HD DVDs and not try to squeeze everything on one HD DVD. I like the current model with DVD utilizing one HD DVD for the main feature and another HD DVD for extras. Now our extras also can be in 1080p. 2) I’m very happy that the DVD Forum is aggressive in the sense of maximizing quality. They require both H.264 and VC-9 which is outstanding. As far as I know they have announced support, perhaps indirectly, that they are seeking to provide lossless compression at 24-bit/48 kHz for pre-recorded Hollywood media. I know Microsoft is pushing this aspect, thank goodness! I have read reports that Microsoft’s lossless compression is superior to MLP in terms of efficiency, but not what other differences exist. The bottom line is that lossless compression guarantees quality identical to the master, PERIOD. You just can’t make this claim with any lossless compression, so let’s end the nonsense once and for all about which lossy codec (Dolby Digital or DTS) degrades the soundtrack the least. Would you not agree that ending the lossy compression wars by simply providing lossless compression would be a significant positive for HD DVD and Blu-ray Disc formats? Knowing that Hollywood studios are not recording in anything other than 24-bit/48 kHz, I think we should be extremely happy to have a primary audio track for Hollywood prerecorded media utilizing 24-bit/48 kHz lossless compression. Lossless compression is realistic, ideal, and absolutely should be implemented for HD DVD and Blu-ray Disc. That’s just my opinion, but I hope others support that view. Of course, having one format emerge is really the key issue. About one format, my understanding is this: HD DVD—1080p 24 frames per second (VC-9 / H.264) + lossless compression for primary audio track for prerecorded movies (as well as Dolby Digital/DTS/MPEG-2) Blu-ray—1080i MPEG-2, Dolby Digital/DTS only (even if 1080p/24, no significant improvement in audio) Yes, the Blu-ray optical drive and disc are superior in terms of “physical” storage space, but that’s it. Blu-ray does not offer more bandwidth as far as I know, although bandwidth is no longer the weakest link anyway. Assuming that VC-9/H.264 provide equal or superior picture quality to MPEG-2, how can you not utilize VC-9/H.264 which is on the order of 250 percent more efficient? Blu-ray is undesirable if they only plan on providing MPEG-2. They end up with 1080i and Dolby Digital/DTS (who even cares if it is slightly higher bitrate Dolby Digital/DTS). My understanding is that Blu-ray ROMs provide 50 GB of storage on a single-sided, dual-layer disc compared to 30 GB for HD DVD that’s about 60 percent more storage space. But then you lose 250 percent due to using MPEG-2 only. So any way you cut it, HD DVD provides approximately 200 percent more storage space by using VC-9/H.264. How can anyone overlook that? Those aren’t small numbers. That 200 percent provides lossless audio compression, higher bitrate VC-9, etc. Sony absolutely NEEDS to provide VC-9/H.264 or I see no reason to support Blu-ray. Sony cannot provide 1080p and a primary lossless 24-bit/48 kHz multichannel soundtrack without providing VC-9/H.264 support. As far as I am concerned, HD DVD is the clear winner until I hear differently. Also, one format is essential. Hopefully, I can read about your opinions in regards to these issues in the next Widescreen Review!
Christian Artman
mailto: drhealthfitness@comcast.net
Editor-In-Chief Gary Reber Comments:
Actually, I am preparing an in-depth article on this very subject for Issue 88, September 2004. But briefly, let me address your questions and assertions. 1. The HD DVD format supports single-sided, dual-layer 30 GB capacity with variable bit rate MPEG-2 up to 36 megabits per second (Mbps), Windows Media Video HD (VC-9), and MPEG-4 AVC (H.264) both with better efficiency for the same picture quality achieved with MPEG-2. (See On Screen conversation on Microsoft.) 2. Lossless linear PCM will be provided. The Blu-ray Disc Founders Group plans to adopt in July at least one of the advanced codecs, either VC-9 or MPEG-4 AVC FRExt, or both.
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