If BD/HD discs have enough capacity to hold audio streams exceeding 5Mbps, why do we need compression formats like Dolby True HD or DTS HD:MA?
I mean why don't they just put the lossless uncompressed LPCM track on the disc? (like some movies do) Is there any advantage to encoding an uncompressed signal into Dolby or DTS that can make the sound quality better? I thought Dolby and DTS (as used on standard DVD's) are just ways to take a high bitrate signal (audio master) and greatly reduce the data stream required without affecting sound quality too much? Reducing the data stream is not necessary any more with BD discs... isn't it?
The transfer to surround and 2 ch is vastly different. Some programme have both, but are altered in the studio to produce pcm. Some issues offer true stereo, others are mixed for 2 channel.
Yup. This is one huge benefit that Blu-Ray has over HD DVD. HD DVD does not have the capacity to have full uncompressed audio like Blu Ray. Going from DTS or DD to Uncompressed is like going Denon to McIntosh. The difference is amazing. If you look at the audio file of the new HD-Audio formats, they are actually smaller than that of a Uncompressed audio file. Marketing hype? yup. Uncompressed takes the cake.
Ahhh... Jan you are probably right... so it is likely the copyright protection benefits that attract FOX to the DTS HD:MA track on all their BD discs....
Would it be safe to say then that Dolby True HD or DTS HD:MA are not capable of producing higher quality sound than uncompressed LPCM? (Of course there are so many other factors that affect sound quality, but all being equal then, theoretically the compressed formats of DTS and Dolby even at their highest lossless spec can not be superior to an uncompressed LPCM track?)
When your amp decodes Dolby or DTS (any version) is the amp not converting it to LPCM anyway ... before sending the signal for power amplification to the speakers...?
It depends on whether you believe bits is bits and digital is perfect. If you do, then what goes into a compressed file is the same as what comes out. Log this in, log that out and they should be the same. No need to listen, the numbers tell you all you require.
DTS Master Audio and Dolby TrueHD are high res uncompressed formats. In fact DTS Master Audio is effectively Meridian Lossless Packing by another name so it is effectively the DVD-A standard which provides for up to 8 channels at 24/192 AFAIK.
Furthermore, my understanding is that LPCM is limited through S/PDIF to 24/96. So in theory the new uncompressed formats available through BOTH BluRay and HD-DVD should be better than LPCM and the traditional lossy compressed Dolby Digital and DTS codecs.
Frank, it seems that a Dolby TrueHD audio file on one of my blu-ray movies, that also has an Ucompressed audio selection, is 11.4 gigs in size. The Uncompressed audio file for this same Blu Ray movie is 24.7 gigs. Im confused, on how they are able to take a Hi-Res Uncompressed file, and make it smaller in size than that of a original Uncompressed audio file, but claim it is better in quality. I know what you said, is what these companies are claiming, but at this time I feel they are full of it. But hey...who knows anymore.lol.
I think it's fair to say that 24/96 is already at least as good (or arguably better) as what the human ear can detect, so if LPCM can do this, why bother with DTS or Dolby high res formats? ...unless either have some advantage in either copy protection or reduction of file size???
(And the whole point of BD discs from the Hollywood perspective, is to make files a huge as possible so you can not download moveis from the internet for free.)
I also heard that DTS HD:MA is lossless packing... yet it is still packing right? Can you pack and still be lossless? Isn't that a contradiction? (I think that is Nicks point.)
Yes you can pack without being lossy. Meridian Lossless Packing is a clever take on zip technology so it packs an audio stream into a smaller space than would normally be the case. The really clever bit which makes it superior to zip technologies is that it does it very fast indeed so the process can be achieved in real time.
Incidentally, the real contradiction is with things liek MP3 and AAC being called 'compression'. They're not so much compressed as thinned out. This si why so many people refer to those codecs as 'lossy compressed', since basically the 'compressed' stream is a copy of the original with about 2/3rds of the bits removed and then packed together (but not cleverly).
It seems that the compressed file size is related to 3 variables: Size of original file, its complexity and duration. A sine wave could be compressed into a value for amplitude, frequency and duration. So a sine wave that would fill a CD could be represented by just a few digits...and take a few kb of memory. But the same CD of music is not nearly so compressible and starting at 650mb, would take lots more to compress. Photographs are the same. In digital photography, a good match for the digital recording problem, I can have a 8 or 10mb 'RAW' file of 12 bit color and no compression. This turns into 5 or 6mb each photo for JPG's at the highest quality with 8 bit color depth. But for screen use, I can crunch a photo down to where 25 would fit on a floppy of 1.5mb and would not make a large print..... This is like the compressed MP3 of photography.
Please don't jump me for dragging photography into this.....saving large photo file sizes is the same problem as large audio file sizes and with similar solutions. math is math.
Just think how much information is jammed onto a nice 12" lp or a roll of film!
When using a Decryption prgram, you are able to look at each individual audio type on the dvd as one single stream, showing the file size. When I do this, I notice that the majority of blu ray movies I own, which is about 40, and about 9 that have both an HD audio format and a Uncompressed audio format, show that the Uncompressed audio Total stream size is larger then that of the HD Audio stream size. Either way, this doesn't matter anymore, as you have explained why this can be possible. Thanks.
Hey Nick, My curiousity wonders how much larger the uncompressed LPCM files are relative to the HD (Dolby, DTSMA) compression files?
From what I have seen, most movies with uncompressed LPCM do not have Dolby HD or DTSMA. (doesn't really make sense to have both) Do you have some BD's having both? For example Fox moives have DTS, but no other formats, many Sony pictures have UncompLPCM but no DTS, etc.
Hey Peter, mainly just comparing separate movies. But for example Spider Man 3 (horrible movie IMO) has both Dolby TrueHD 5.1 AND Uncompressed PCM 5.1. The total stream size for the Dolby TrueHD is smaller than that of the total stream size of the Uncompressed PCM 5.1. A few movies have both DolbyHD and Uncompressed, but not many. And I have not seen ANY yet that had both Uncompressed PCM AND DTS-HD. But your right, almost all Blu-Ray only have one or the other.