Re: Writing a letter to Warner about lack of lossless audio on their BRD
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| True, but in at least one instance (Universal's U-571), it was noted almost immediately after the Blu-ray was released that the image was less detailed (though not hugely so) than on the previous HD DVD. And my source, who gets it directly from Universal, tells me that this is a deliberate trade-off to give the lossless crowd (that would include you, David) what they want, even if it means compromising the image quality. |
Providing lossless wasn't the mistake: it shouldn't be assumed that audio gets short-changed either. our HD format supports both advanced audio and video. Not just video.
But that's not to say that there aren't options for optimizing AV for challenging content. For instance, rather than sacrifice lossless altogether, other compromises can be made that aren't ideal for audio, but that can free up more bit space for video while not resorting to lossy compression. So far all of the Universal titles I've seen have been 24-bit DTS Master Audio. Dropping down to 16-bit would cut bit space dramatically (I know with Dolby TrueHD, dropping from 24 to 16 cuts the file size almost in half. Not sure of the exact reduction for DTS master, but it's got to be significant). I don't have that particular Universal disc so I can't vouch for the bit-depth, but I'd presume it's 24 bit like the rest of the DTS tracks from Universal.
As video compression practices improve, we should be able to see lossless audio and uncompromised video even for challenging titles like this. New Line has insisted, for instance, that with careful compression they can provide lossless audio along with the extended cut for LOTR on a single BD50 without any negative impact on PQ. Most compressionists say that the space for lossless doesn't have to necessitate compromised video qualtiy for challenging titles, only that with challenging material it might mean more time and money need to be spend on the video encode to hand-tweak it. Perhaps Universal didn't want to make the additional investment with hand-tweaked compression and so added filtering so they could just set the average-bit-rate dial and go. In any case, it might be prudent for studios to forgo the most challenging compression jobs right now as practices continue to improve (and BD50 replication becomes more plentiful), and then revisit those same titles in a few years when superior compression won't require additional cost.
As an example of how compression technology improves over time, remember the first Titanic DVD release? both Fox and THX said that they purposefully went with a 4x3 lbxed image rather than 16x9 because they felt that the added picture information with a 16x9 capture would be too difficult to compress on a dual-layer DVD given the high entropy and run time of the film. At that time in DVD's life cycle, that might have been a true statement. However, a few years later, Fox re-released Titanic on dual-layer DVD with a reference 16x9 anamorphic picture. In the intervening years compression technology had improved to the point that the same bit-space could be more efficiently utilized by the MPEG2 codec, allowing a full 16x9 capture without increased artifacting or high frequency filtering.
AVC and VC-1 compression will have a similar improvement curve (so say all the compression experts). If not today, then a few years from Now Universal will be able to re-release that title with optimal image and lossless audio without the challenges incurred today.