Why no mordern video codec or hi-rez audio?

[Molin]

My understanding is that Blu-Ray will use MPEG-2 combined with Dolby Digital for pre-recorded media. Of course it is natural to support these formats for direct recording of DTV on writeable media. But why use a video codec that is even now getting old for pre-recorded stuff?

Newer video codecs, such as H.264 or Windows Media 9 are much more efficient than MPEG-2 and gives a higher quality image on even lower bitrates. If they are used, Blu-Ray would have a significant advantage over HD-DVD since can hold 20GB more date. This space could be used for more extras, high quality audio or better quality video using 10 bits or even 4:4:4 video.

And on the audio side, I think there should be support for one high resolution lossless format like MLP. When so much effort is put into high quality video, why so little focus on audio? Just listen to the difference on a recording in Dolby Digital and in SACD (where it is possible), and it is obvious that something better than DD is needed in mordern formats.

I would like to support Blu-Ray specially since it higher capacity, but as of now I prefer HD-DVD mainly since it seem to have support for high quality audio.

Best regards,
Per Molin

[Psychogenicscc]

Originally Posted by Molin

My understanding is that Blu-Ray will use MPEG-2 combined with Dolby Digital for pre-recorded media. Of course it is natural to support these formats for direct recording of DTV on writeable media. But why use a video codec that is even now getting old for pre-recorded stuff?

Newer video codecs, such as H.264 or Windows Media 9 are much more efficient than MPEG-2 and gives a higher quality image on even lower bitrates. If they are used, Blu-Ray would have a significant advantage over HD-DVD since can hold 20GB more date. This space could be used for more extras, high quality audio or better quality video using 10 bits or even 4:4:4 video.

And on the audio side, I think there should be support for one high resolution lossless format like MLP. When so much effort is put into high quality video, why so little focus on audio? Just listen to the difference on a recording in Dolby Digital and in SACD (where it is possible), and it is obvious that something better than DD is needed in mordern formats.

I would like to support Blu-Ray specially since it higher capacity, but as of now I prefer HD-DVD mainly since it seem to have support for high quality audio.

Best regards,
Per Molin

Dude all that comes later, Not right away!!!! The reasoning behind this is COST!!! Right now Sony and others are trying to make BD as cheap as Possible.

[Kitsunebi]

They have to finalize these things at some point, don't they?

I keep hearing that they are only planing on using MPEG2 because the newer codecs arn't quite as good in picture quality. I don't know how much truth is in that, but it does seem a little silly to me to not support a "better" video codec.

On a side note, I read on Slashdot that BBC R&D is working on an open-source codec Dirac.
"Dirac is a general-purpose video codec aimed at resolutions from QCIF (180x144) to HDTV (1920x1080) progressive or interlaced. It uses wavelets, motion compensation and arithmetic coding and aims to be competitive with other state of the art codecs."

They also say, "Our algorithm seems to give a two-fold reduction in bit rate over MPEG-2 for high definition video (e.g. 1920x1080 pixels), its original target application." I don't know if it will get anywhere, but if it turns out to be good, it might be a good option.

[Blu-Wave]

Using MPeg2, 1920 by 1080 pixel HDTV doesn't leave a great deal of bandwidth out of 36Mbps for uncompressed 7.1 channel SACD quality audio - even though 50GB dual-layer Blu-ray has the space for it. HD-DVD, with only 30GB, hardly has enough space as it is.

MPeg4 is available - and Sony's Playstation Portable [PSP] will use it to give two hours of high DVD quality on a single 1.8GB Universal Media Disc [UMD] - but HDTV involves six times as many pixels as NTSC, and low cost MPeg4-based HDTV compression hasn't been developed yet - even though MPeg2-based HDTV compression is pretty well developed. Like most modern compression schemes, MPeg4 accommodates wavelet and fractal compression, etc. and is significantly more efficient than 1980s MPeg2 technology - as well as producing less noticeable artifacts.

The mass market is happy with CD, Dolby Digital and DTS quality sound, and until MPeg4-based HDTV compression comes down in price, the current 36Mbps bandwidth leaves little room for high quality audio. But Sony (and Phillips) developed SACD to be the next generation audio carrier after CD, so as soon as there is space in the Blu-ray data envelope (i.e. when MPeg4 hits HDTV), they are likely to offer it as an option.

With HD-DVD, it is easy to promise many things based upon hypotheticals, but Blu-ray exists as a product right now - and if Sony haven't included SACD quality audio yet you can be sure that it's not because they don't want to... :?

[Rash]

I really didn't know MPEG4 was that expensive. Where did you hear that?

[Blu-Wave]

Although it is more computationally intensive than MPeg2, typical MPeg4 components aren't much more expensive than MPeg2 components these days at PAL and NTSC resolutions or lower - due to mass-production. But high definition involves around six times the data-rate of PAL or NTSC, so unfortunately you can't just use the same chipsets.

MPeg2 is already well established as the primary compression technology for standard and high definition distribution - allowing costs to have fallen significantly within the professional arena. However, as computer components become cheaper and more powerful and high definition goes mass-market - increasing the demand for bandwidth, expect to see MPeg4 or better take over from MPeg2 in the professional arena in a few years time.

MPeg4 will arrive in consumer high definition products, but unless and until the cost comes down substantially they're not likely to include more expensive HD compression technology in early products trying to gain market share when 50GB discs can already hold four hours of high definition video. They might include MPeg4 capability when recording standard definition video though - potentially giving a day or more of high DVD quality timeshifting or archival on a single 50GB disc.

[Rimmer]

I will be very disappointed if Blu-Ray discs don't carry a primary lossless audio soundtrack in addition to the obligatory DD 5.1 track.

Lossless audio compression can achieve a bit rate of 2 to 3 Mb/s at 48khz, 24-bit 5.1. That adds up to approximately 2GB for a two-hour movie - only 4% of the 50GB storage capacity. I can understand why MPEG-2 might be the more economical video codec, but there is no reason not to use lossless audio on Blu-Ray.

[Blu-Wave]

Lossless is one thing, but whilst 48kHz/24bit is better than CD (which is better than DD/DTS), it's hardly high resolution audio. 96kHz/24bit is better again, but the difference in sound quality between 96/24 and 192/24 is obvious - often within a couple of seconds. Similarly, 2822kHz/1bit SACD is clearly much better than 96kHz/24bit PCM - and it also provides 5.1 multi-channel sound on a "DVD" (SACD). Unfortunately, the datarate of DVD (9.6Mbps) prevents it from carrying multi-channel 192kHz/24bit audio - this is only available in stereo. However, BD would be capable of 192kHz/24bit 5.1 or even 7.1 along with MPeg4-based high definition video.

Note that Meridian Lossless Packing [MLP] is an entropy-based coding scheme, and because real instruments generate relatively little information beyond 50kHz, significantly more compression will be possible on a 192/24 or even 384/24 signal than a 48/24 or 96/24 signal. So even if a high sample rate is used for the purposes of high fidelity, it doesn't mean that the data rate need be much greater than that of low fidelity 48/24 or 96/24...

Interestingly, Digital Theatre Systems [DTS] is currently developing a lossless system to deliver up to 96kHz/24bit soundtracks to cinemas. At least if they're starting to think of lossless audio in the cinema there's a chance of such soundtracks (possibly converted to MLP) appearing on high definition films that we can buy and play at home...

Unfortunately, whilst simple in concept, MLP is pretty complex to implement, and it is likely to be quite a while before we see home audio recorders offering real-time MLP compression. ...Although the compression could always be performed offline, in the background, and then written to disc when ready... :?

[Rimmer]

Agreed, 24-bit/48kHz is not high-resolution, but I think it's the best we can realistically hope for from the next gen movie formats as things currently stand. Besides, at the moment the dialog and foley effects on movies are recorded at 20-24bit/48kHz anyway so higher res wouldn't benefit current movies that much. My view is that lossless 24/48 should be the minimum quality we expect from Blu-Ray pre-recorded video discs as it it would be a big step forward from DD/DTS.

[Blu-Wave]

...but given that BD offers the maximum video quality we can expect in the home for some time, it would be sad if its sound quality was limited to the minimum. I know that 48kHz/24bit is dominant in the film industry at the moment, but even DTS are actively developing 96kHz/24bit 7.1 in cinemas - similar to DVDA multi-channel.

Older analogue film soundtracks will be more faithfully preserved in 96/24, and whilst waiting for film sound quality to improve, music concerts in HD plus 96/24 7.1 or preferably 192/24 7.1 audio would be a very attractive feature, and would allow the BD machine to be ready for films with high definition audio when it arrives.

As I mentioned earlier, entropic coding would allow 192/24 7.1 to take up not much more space (and bandwidth) than 96/24 7.1. If BD50 had difficulty fitting a whole HD film on one disc, then there would be a reason for drastically limiting the audio capability from the outset. But it doesn't, and a high quality audio-visual experience requires both audio and video. :?

Nearly all current Sony CD players are now SACD-capable, there are many low cost DVDA players, and even universal machines for a few hundred pounds. It would be sad if early (and relatively expensive) BD machines restricted their appeal to the very types of buyers who are likely to buy early machines, by not supporting SACD/DVDA quality audio - and if they can support playing legacy SACDs and DVDAs (which many early buyers are likely to have) then it makes sense to have it available on BD as well - initially for music concerts and then later for films.

[Rimmer]

I agree with you absolutely. 24/48 is good; 24/96 is significantly better; while 24/192 or SACD is the ultimate!

What worries me is that we may not get any improvement on existing DVD-Video audio quality at all. I would love to have lossless high res audio on Blur-Ray discs, but if we aren't going to get that due to lack of disc space on MPEG-2 encoded discs, then we should at least get 24/48 as it's the next best thing. I suppose we'll just have to wait and see what is on the table when the specs are formalized.

[Blu-Wave]

Whilst films might be stuck at 48kHz for a bit - not least due to bandwidth limitations - 36Mbps might be a lot more than the 9.6Mbps of DVD, but using MPeg2 high definition needs around 24Mbps sustained, leaving little bandwidth for high definition audio multi-channel anyway. MPeg4 at 12Mbps or so would not only free up bandwidth for high definition audio but would also avoid those highly unnatural "blocky" artifacts we've all grow to loathe - I mean love - in MPeg2. Then again, Sony have 72Mbps and 144Mbps Blu-ray technology on the market, but that would push up the price... :?

Forgetting about high definition video for a moment, legacy playback of CDs, DVDs, DVDAs and SACDs will require high resolution (definition) audio anyway - Sony include (stereo at least) SACD-capability on nearly all their CD players now - it would be strange if their mass-market BD machines couldn't play it too, whilst other manufacturers have pushed DVDA right down the price bracket too. Perhaps we'll see Sony's first universal machine? We might even get a new audio-only standard - perhaps with height channels too - that blows the socks off DVDA and SACD? But probably not in early machines.

Note that Sony's CinaAlta range of high definition cameras and recorders already use MPeg4 compression to get the data on to tape, but not for the kind of major interframe compression required to get the datarate down to 20Mbps or lower.

Talking of 192kHz being the ultimate, Ken Ishiwata of Marantz and hi-fi in general fame has experimented with 384kHz up to 500kHz, and comments that the improvement (over 192kHz) is pretty obvious. DSD (as used in SACD) also has fewer audible artifacts than PCM, but would also benefit considerably from increasing the sample rate beyond 10MHz - significantly reducing the amount of noise-shaping required, for example.