With lossless PCM, why the need for TruHD/DTS-HD MA?

[panlee]

My understanding is Lossless PCM is the ultimate track, the best the sound is meant to be. TruHD and DTS-HD MA after decoding will be equal to the PCM track. Beside the space savings, is there any advantage to have TruHD and DTS-HD MA? Am I right to say that with 50G Blu-ray, there really isn't a need for TruHD/DTS-HD MA? Should Dolby and DTS be worry?

[khwiggins2]

It's cheaper to encode a film in VC-1 and True-HD and put it on a BD25 than it is to encode it in MPEG-2 with PCM and have to put it on a BD50. Or it will be anyways when the sales volume increases for hd-dvd and blu-ray.

[nataraj]

PCM is waste of space. You like wasting space - then support PCM.

Remember video is still highly compressed ... personally I'd rather have lesser compression of video or more extras.

[Ruined]

In addition to the "waste of space" that PCM creates that could be better used for extras, interactivity, etc, the PCM tracks that have been featured on Blu-Ray have been almost all 16bit/48khz. Using less space, TrueHD can do 24bit/48khz! So you can get higher bit-resolution with TrueHD using less space!

[vairulez]

what's more if MMC ever becomes a reality, you'll be happy to have truHD instead of PCM

[Forceflow]

Originally Posted by vairulez

what's more if MMC ever becomes a reality, you'll be happy to have truHD instead of PCM

great point!

[bfdtv]

Originally Posted by panlee

Beside the space savings, is there any advantage to have TruHD and DTS-HD MA?

All modern films are mastered with 24/48 audio. Employees at these mastering facilities, as well as the individuals doing the theatrical mixes, have said as much on this forum. Even paidgeek has said as much over on the Industry Insiders thread. [Older movies, without a recent audio remaster, are 16/48.]

Due to the high bandwidth and space requirements of uncompressed audio (LPCM), most studios downconvert 24/48 master audio to lower 16/48 fidelity for use on Blu-ray disk. Only a small number of Blu-ray disks with LPCM feature master quality audio; more than 85% of all releases with LPCM feature inferior 16-bit audio. Paidgeek -- the representative from Sony Home Video -- has said several times over in the HDTV Software Media forum that Sony intends to stick with 24-bit -> 16-bit downconversion on LPCM releases for the forseeable future, due to bandwidth constraints.

Note Sony Home Video recently decided to make more use of TrueHD on future titles to deliver the full 20-bit / 24-bit fidelity of the master.

Rather than downgrade the 24/48 master audio to lower 16/48 fidelity, some studios (FOX) have chosen to losslessly pack or "zip" these audio masters with DTS-HD MA or Dolby TrueHD. Once unpacked or "unzipped" by a player or future HDMI 1.3 receiver, the resulting output is a 24/48 LPCM track that is bit-for-bit identical to the original studio master.

LPCM
2 hours @ 5.1 16/48 LPCM = 4.14 Gbytes @ 4.6 Mbps (used on most Blu-ray titles with LPCM)
2 hours @ 7.1 16/48 LPCM = 5.52 Gbytes @ 6.13 Mbps
2 hours @ 5.1 24/48 LPCM = 6.21 Gbytes @ 6.9 Mbps (used on Disney Blu-ray titles with BD50 + AVC)
3 hours @ 5.1 24/48 LPCM = 9.32 Gbytes @ 6.9 Mbps
2 hours @ 7.1 24/48 LPCM = 8.28 Gbytes @ 9.2 Mbps
3 hours @ 7.1 24/48 LPCM = 12.42 Gbytes @ 9.2 Mbps
2 hours @ 7.1 24/96 LPCM = 16.56 Gbytes @ 18.4 Mbps
3 hours @ 7.1 24/96 LPCM = 24.84 Gbytes @ 18.4 Mbps

Dolby TrueHD (comparable to DTS-HD MA)
2 hours @ 5.1 16/48 TrueHD = 1.26 Gbytes @ 1.4 Mbps ABR (used on Warner HD-DVD releases)
2 hours @ 5.1 24/48 TrueHD = 3.06 Gbytes @ 3.4 Mbps ABR (used on recent HD-DVD releases from Universal)
3 hours @ 5.1 24/48 TrueHD = 4.59 Gbytes @ 3.4 Mbps ABR
2 hours @ 7.1 24/48 TrueHD = 4.23 Gbytes @ 4.7 Mbps ABR
3 hours @ 7.1 24/48 TrueHD = 6.35 Gbytes @ 4.7 Mbps ABR

Both TrueHD and DTS-HD MA use variable bit rates, so the bit rate varies by the "complexity" of the soundtrack during the film. The ABR notation above refers to average bit rate.

Originally Posted by panlee

Am I right to say that with 50G Blu-ray, there really isn't a need for TruHD/DTS-HD MA?

The BD50 format alone does not eliminate the need for TrueHD and DTS-HD MA. If studios were to use BD50 with AVC (or VC-1) encoding, with few extras, then there would be no need for TrueHD and DTS-HD MA on most movies -- and 24/48 LPCM would be fine.

Unfortunately, as of last month, 80% of announced, upcoming Blu-ray titles use BD25, and more than two-thirds of the remainder slated for BD50 use MPEG-2. Moreover, studios are expected to add more and more extras to their disks. Later this year, we're expected to see the first Blu-ray releases with BD-Java and true PIP commentary, which will subtract additional bits from the available mux rate.

With BD25, you can forget 24/48 LPCM on all but the shortest movies. Even with BD50, LPCM at master quality 24/48 significantly eats into available peak video bandwidth -- and hence picture quality -- when MPEG-2 is used. Assuming no extras with BD50, the A/V mux rate of 48Mbps is available for the full length of all films shorter than 2.3 hours (139 minutes); on longer films, the available mux rate is less. Subtract 7.1 24/48 LPCM from the 48Mbps A/V mux rate and you're left with with a bit over 38Mbps. Subtract the three foreign language tracks in 640Kbps Dolby Digital and you are left with 36Mbps and change. Subtract the picture-in-picture video commentary featured on upcoming BD-Java disks and you are left with 30-32Mbps. Subtract overhead and interactivity and you're left with 29-31Mbps. If all studios were to abandon MPEG-2 in favor of AVC, that would be fine for movies of typical length, but that's not going to happen.

When less than 10% of announced Blu-ray titles feature the combination of BD50 and AVC -- as of last month -- we need the advanced audio codecs to get master quality, 24-bit / 48kHz audio.

Do TrueHD and DTS-HD MA sound better than LPCM?

Assuming no dialog normalization is used, 24/48 TrueHD and DTS-HD MA will output sound that is bit-for-bit identical to 24/48 LPCM. Such 24/48 TrueHD and 24/48 DTS-HD MA tracks are higher quality than the downconverted 16/48 LPCM tracks found on most Blue-ray titles.

Dolby TrueHD and DTS-HD MA are just lossless packing methods for LPCM. Said a different way, they are basically zip files containing LPCM. This lossless packing may be unnecessary on most BD50 disks with AVC video, but again, only a small minority of announced titles actually use the combination of BD50 and AVC. Examples of Blu-ray releases with 24/48 LPCM tracks include Chicago, Ladder 49, Pearl Harbor, The Prestige, and The Wild. Except for The Wild, all of these are BD50 releases, and four of them use AVC.

Originally Posted by panlee

Am I right to say that with 50G Blu-ray, there really isn't a need for TruHD/DTS-HD MA?

What about longer films?

Even if all studios were to use the combination of BD50 and AVC, that might still prove inadequate for high-fidelity 24/48 LPCM audio on the longest films, particularly as studios add more interactive disk features. Recall that the full 48Mbps disk A/V mux rate is only available for the full duration on titles with a runtime of less than 139 minutes, assuming no extras. Consider the film Dances with Wolves. This has a run time of 226 minutes, which means that the average bit rate available for that title on BD50, assuming no extras is approximately 29 Mbps.

Subtract 7.1 24/48 LPCM from that and you're left with with a bit under 20Mbps. Subtract the three foreign language tracks in 640Kbps Dolby Digital and you are left with 18Mbps and change. Throw in a picture-in-picture video commentary featured on upcoming BD-Java disks and you're left with 12-14Mbps ABR for video. Does that sound good to you?

[eightninesuited]

Originally Posted by Ruined

In addition to the "waste of space" that PCM creates that could be better used for extras, interactivity, etc, the PCM tracks that have been featured on Blu-Ray have been almost all 16bit/48khz. Using less space, TrueHD can do 24bit/48khz! So you can get higher bit-resolution with TrueHD using less space!

There have been plenty of 24/48 PCM tracks from Disney on Blu-ray. There's not a single True HD 24bit track on either Blu-ray or HD DVD edit: (as far and I know).

I support the use of True HD over PCM, and both formats are relatively young. We'll see a move towards True HD soon. I think DTS MA will only be used by Fox. DTS has dropped the ball already by not being able to provide decoders.

[indian]

good things come to those who wait. keep it up fox!while you're at it, put some movies out!

[SirDrexl]

Saving space is all the advantage the lossless compression codecs need.

[bfdtv]

Originally Posted by eightninesuited

There have been plenty of 24/48 PCM tracks from Disney on Blu-ray. There's not a single True HD 24bit track on either Blu-ray or HD DVD.

I wouldn't call 8 titles "plenty." Remember, some of the early Disney titles announced as 24/48 ended up being 16/48, with the MPEG-2 encode requiring more bandwidth than first anticipated. FOX has almost four times as many titles with 24/48 DTS-HD MA.

IIRC, there are at least two Blu-ray titles with TrueHD. I believe Legends of Jazz has a 24/48 TrueHD track, but I'm not sure about Nine Inch Nails Live. On HD-DVD, Universal has used 24/48 TrueHD with several recent film releases.

I support the use of True HD over PCM, and both formats are relatively young. We'll see a move towards True HD soon. I think DTS MA will only be used by Fox. DTS has dropped the ball already by not being able to provide decoders.

I agree that DTS did not do a good job of working with SoC vendors like Sigma, Broadcom, and others to ensure that those solutions had the DSP performance necessary to decode the DTS-HD MA format. That said, they appear to have rectified that problem for the next-generation. Sigma Designs has indicated they have a new version of their SMP8634 in sampling that adds the processing power necessary to decode DTS-HD MA. I suspect we will see this new chip in Profile 1.1 players coming late this year and early next.

[javayoda]

Originally Posted by eightninesuited

There have been plenty of 24/48 PCM tracks from Disney on Blu-ray. There's not a single True HD 24bit track on either Blu-ray or HD DVD.

I'm confused - does that mean there are no master quality audio tracks on HD-DVD? Or does HD-DVD support master quality (24-bit) with another codec?

[wormraper]

Originally Posted by joshd2012

The only people who think PCM is a waste of the space are those who can't enjoy it because of their format selection.

Oh good Lord!!!!, that's so much bull. Anyone would love lossless audio but that's like saying that people who prefer Flac or WMA lossless instead of uncompressed wave are idiots. Maintaining the same quality with less space used is beneficial to anyone. Stop making cheap shots.

[bfdtv]

Originally Posted by javayoda

I'm confused - does that mean there are no master quality audio tracks on HD-DVD? Or does HD-DVD support master quality (24-bit) with another codec?

Well, mastering in 24/48 only become 'industry standard' in the past five years or so. Films older than that may or may not have 24/48 audio masters.

I don't know if Universal uses dialog normalization, but End of Days and Fear and Loathing in Las Vegas both have 24/48 TrueHD tracks.

BTW regarding space all you are saving is a few gigabytes. With BD50 this is even less of a concern. You can only say that PCM is comprising the disc if the disc is completely filled to the brim. But we see lots and lots of discs that have gigabytes of blank space on them. So using lossless would make no difference. Theres no need to save space just for the sake of saving space.

Space isn't the only concern. As I noted above, bandwidth is too, especially for titles using MPEG-2. Video gets priority, so that encode gets done first, and the peaks there determine what sort of audio is possible. Of course, they've also got to account for the 640Kbps DD foreign language tracks, overhead, and on future titles, picture-in-picture.

[nataraj]

Originally Posted by joshd2012

The only people who think PCM is a waste of the space are those who can't enjoy it because of their format selection.

Oh please. Can you keep the format battle out of this - and not peddle snake oil for partisan benefit.

[UxiSXRD]

Ever since getting my HDMI receiver and experiencing the PCM tracks for Black Hawk Down and Pearl Harbor, I really do wish PCM was mandated in Blu-ray. 16/48 at the very least is reasonable. The Prestige sounds pretty good, too (my latest BD).

As benes said, very very few BD50 have maxed out their space. The bandwidth bit bucket has more than enough space available for 7.1 uncompressed for most features... MPEG2 will eventually go away in favor of AVC. In rare cases, for the longest movies, I could definitely see a use for TrueHD and/or DTS-HD, though...

I'd prefer all non-movie extras go onto a separate disc that I can safely ignore or pursue, at my whim.

[homerx]

Originally Posted by javayoda

I'm confused - does that mean there are no master quality audio tracks on HD-DVD? Or does HD-DVD support master quality (24-bit) with another codec?

Most of the studio cannal HDDVDs have DTS MA tracks on them. Not sure what their encoded at...
So hopefully toshibia puts out a patch that allows full decoding of the DTS MA tracks. I think they down convert them now...


But on the terms of LPCM. I think it can allow for a great sound experence if done right. However dolby true HD and DTS MA can offer the same exact sound at a higher compresion rate. Its a lot like VC1 vs Mpeg2 or 4. VC1 takes up less space. But do to a better compression style it can offer better over all PQ at or bellow equal bitrates.

[Phloyd]

Originally Posted by nataraj

PCM is waste of space. You like wasting space - then support PCM.

Remember video is still highly compressed ... personally I'd rather have lesser compression of video or more extras.

Ben Wagonner has told us that VC-1 doesn't improve with less compression of the video. He is an expert and should know what he is talking about.

So all of the BD 50 discs that Warner has released have 20GB of extra space on them that would allow PCM with no extra cost and no loss to the image.

As Benes pointed out, many BD50 titles including Disney titles do not use the full 50 GB so really there is no loss from having PCM on these discs.

With the move towards BD50 and AVC from Bluray studios, PCM is not a liability and has better compatibility than the lossless codecs.

[UxiSXRD]

Originally Posted by benes

Plenty of bandwidth in bluray too. 48Mbps available for the total mux. The largest PCM track on your list is 18Mbps. That means you are still left with 30Mbps of bandwidth, which coincidentally enough is the maximum for HDDVD. If thats not enough for VC1 and AVC then HDDVD is in trouble.

Excellent point.

Originally Posted by benes

I'll accept your point on MPEG2. But it seems clear that everyone is moving away from that codec including Sony. And for that matter they are even moving away from PCM itself so this whole argument may be moot soon.

One other thing worth adding is that if space itself is a concern, then that makes an argument for BD75/100/200 rather than an argument against PCM. I would prefer we could ditch video compression, as well, but that's just not feasable right now (HVD discs, where art thou?!). Uncompressed audio has already been achieved without impact to PQ, and I'm 100% for avoiding compression if/when possible without impacting PQ.

Originally Posted by benes

On a related note the recent Identity disc has 3 PCM tracks totaling almost 14Mbps. But they still had enough room for 4.5stars worth of video. Using AVC of course.

Originally Posted by Phloyd

So all of the BD 50 discs that Warner has released have 20GB of extra space on them that would allow PCM with no extra cost and no loss to the image.

Moreover, Warner has for some reason left TrueHD off of many Blu-ray titles when it was present on the HDDVD titles. I have read that PCM is comparably very easy to mix in so shouldn't really raise a cost issue, either... But then Warner would be moving to true neutrality, if not a Blu-ray favorable audio quality, then, and we just couldn't have that.

[Wesley5]

I am not an audiophile, but I do know PCM means uncompressed audio, which is totally different from lossless, which I take to mean same as the master. PCM may be lossless, but majority releases with PCM so far seem to be down sampled from the masters. By same token, "lossless" tracks from lossless codecs may or may not be equivalent to masters.

A losslessly compressed tracks with higher resolution (say 20/48) would give better AQ than uncompressed 16/48 PCM. People need to take this into consideration when comparing PCM with losslessly compressed tracks.

[nataraj]

Originally Posted by joshd2012

The numbers don't lie.

Then show me some DBT results.

[nataraj]

Originally Posted by Phloyd

Ben Wagonner has told us that VC-1 doesn't improve with less compression of the video.

Why do you care ? Afterall according to you there is no worse sin than being employed by MS

[ChrisWiggles]

Originally Posted by panlee

My understanding is Lossless PCM is the ultimate track, the best the sound is meant to be. TruHD and DTS-HD MA after decoding will be equal to the PCM track. Beside the space savings, is there any advantage to have TruHD and DTS-HD MA? Am I right to say that with 50G Blu-ray, there really isn't a need for TruHD/DTS-HD MA? Should Dolby and DTS be worry?

No they shouldn't be worried. We live in a world where space and bandwidth are not infinite. As such, space savings are not irrelevant.

[draggoon01]

5.1 24/28 is the standard to look at. movie theatres use 5.1 not 7.1 although there may be a few special 7.1 mixes made for HDM, 7.1 will not be common and should not be used as an arguing point

most movies are under 2hr 30min. using an extreme example like dances with wolves at 3hr 46min should not be used as an arguing point. secondly a movie that can justify being over 3hr long will most likely be released on 2 discs by studios, regardless of what can fit on one disc.

although there are issues with some bluray using bd25 or mpeg2, it is already being less of a problem now and will be less so in the future. all bluray players support bd50, avc/vc1, and pcm. suggesting that something like truehd/dts-hdma be implemented to fix this, which is NOT part of the spec, will make things worse.


if we look at a 3 hour movie:

video @ 20 Mbits = 27 Gbytes
audio @ 5.1 24/48 LPCM = 9.3 Gbytes
PiP @ 4Mbits = 5.4 Gbytes
foreign languages @ 4Mbits = 5.4 Gbytes
---
total = 47.1 Gbytes

leaving 2.9 Gbytes for few small extras (some hd trailers + 1hour sd footage), but again you're more likely to have a second disc in this situation. and the 20 Mbits for video is being generous, as is 4Mbits for PiP


for bluray the biggest reason to use truehd or dts-hdma is for advertising factor

hd-dvd could use the space saved by truehd but blu-ray doesn't really need it

[bfdtv]

Originally Posted by draggoon01

video @ 20 Mbits = 27 Gbytes
audio @ 5.1 24/48 LPCM = 9.3 Gbytes
PiP @ 4Mbits = 5.4 Gbytes
foreign languages @ 4Mbits = 5.4 Gbytes
---
total = 47.1 Gbytes

leaving 2.9 Gbytes for few small extras (some hd trailers + 1hour sd footage), but again you're more likely to have a second disc in this situation. and the 20 Mbits for video is being generous, as is 4Mbits for PiP

You aren't leaving much space for deleted scenes. Or what about space for seamless branching if a studio -- like Sony -- wants to put the theatrical release and extended cut on the same disk?

You're also forgetting about bandwidth. Many Blu-ray titles with AVC video average less than 20Mbps, but peak at 35Mbps or more during the most intensive scenes. Subtract 35Mbps from the 48Mbps A/V mux rate and you are left with 13Mbps. Subtract 5.1 24/48 LPCM and you are left with 6Mbps. Subtract three foreign language tracks in 640Kbps DD5.1 and you are left with about 4Mbps. That might be enough if the PIP was encoded with AVC, but I'm betting much of the PIP will be encoded with MPEG-2, as is the case now on HD-DVD titles.

[paintit77]

LPCM Is free. DTS-HDMA and Dolby True-HD cost money to encode in. MPEG2 needs to go away on single layer disks. I think the sweet spot is VC-1 or AVC for Video and DTS-HDMA and Dolby True-HD for audio. Then dump the extras on another single layer disk. I would be very happy if all the BR studios used this method from now on. LPCM like MPEG2 are useless for single layer BR movies. There is no need for Dual Layer if they use the newer audio and video encoders. AVC is really coming on fast with its ability to offer the same quality as VC-1. It definetly has a different look.
What really sucks about it is trying to use it on a PC! It took me 30 minutes to encode 5 minutes worth of HDV footage.

[bfdtv]

Originally Posted by paintit77

LPCM Is free. DTS-HDMA and Dolby True-HD cost money to encode in.

That is inaccurate. Update: This is very misleading, it is not technically inaccurate.

Dolby -- on this very forum -- and DTS have said there is no licensing cost to use TrueHD and DTS-HD MA on Blu-ray and HD-DVD titles. Both are free for any studio to use on their titles.

The decoder in the player and/or the professional tool suites to create those encodings may not be free, but it is obviously in the best interest of Dolby and DTS to get decoding for their codecs in as many players as possible.

[bfdtv]

Originally Posted by benes

They are VC1 not MPEG2. And they use less than 1.5Mbps of bandwidth.

Is that what they are using now? If so, that is good news.

I know that last fall, Amir (and Cjplay?) said the mux tools did not support IME in anything but MPEG-2. Amir mentioned periodically that they were working on new tools to support the use of VC-1 for IME, which was to free up more bandwidth for feature encodes and lossless audio tracks.

[UxiSXRD]

Originally Posted by bfdtv

That is inaccurate.

Dolby -- on this very forum -- and DTS have said there is no licensing cost to use TrueHD and DTS-HD MA on Blu-ray and HD-DVD titles. Both are free for any studio to use on their titles.

IIRC, Dolby said that provided the licensing was paid for the legacy DD, there was no additional charge for TrueHD or DD+, but there was still the original fee. Seeing how almost everything includes a legacy DD 5.1 makes that distinction mostly moot, though.

I don't recall anything from DTS but I imagine it's a similar situation for DTS-HD. Not that legacy DTS was ever as common as some of us might have preferred, so probably a different overall situation. YMMV. I'll be happy when there's anything that can decode full lossless DTS-HD Master Audio...

[bfdtv]

Originally Posted by UxiSXRD

IIRC, Dolby said that provided the licensing was paid for the legacy DD, there was no additional charge for TrueHD or DD+, but there was still the original fee. Seeing how almost everything includes a legacy DD 5.1 makes that distinction mostly moot, though.

As you know, the Blu-ray specification mandates that every title with TrueHD include a DD5.1 track for backward compatibility. Every DTS-HD MA title includes a "core" DTS track for backward compatibility. There is no scenario where a studio would pay more in licensing, unless they put LPCM audio on the disk and nothing else**. As you say, it is probably more accurate to say that using those codecs involves no extra cost in licensing, rather than being free.

** The Blu-ray specification requires that studios include at least one of the following tracks on every title: Dolby Digital, DTS, or LPCM. Although it is not common practice, a studio could theoretically include 5.1 LPCM and no Dolby Digital or DTS 5.1 track for backward compatibility, thereby avoiding the licensing costs. Warner did this with the release of Sopranos, Season Six on Blu-ray.