Ask questions to BD authoring and compression insider "2themax"

[2themax]

Originally Posted by DaViD Boulet

welcome!

I'm wondering if you can point to why studios like Disney, Fox, Sony, and MGM provide lossless-quality audio (in whatever form) on BD but studios like WB fail to provide it even for the majority of their titles.

Those of us who enjoyed laserdisc know that lossless audio improves fidelity even when the source material is generally what folks would consider "limited quality", such as optical mono soundtracks or old mag stems from the B&W era. I'm astonished at how much more open and natural the PCM of It's A Wonderful Life sounds, for instance, on laserdisc versus the lossy Dolby on DVD. When I see Warner continue the practice of lossy audio on BD, it does not bode well for the HT community.

Can WB be "taught" that lossy really does matter and that it's a feature that should be considered standard regardless of how well or poorly their techs deem the quality of the source-material to be encoded?

While I don't know for sure, I would assume that it was (is) related to them being neutral and trying to keep titles equal on both sides of the fence. Going forward from May though, that obviously is no longer an excuse. The only other possibility I can think of would be that the majority of their authoring is done in-house so there isn't anyone saying "hey, our other customers do lossless, why don't you?"

[patrick99]

Originally Posted by 2themax

How about I offer some numbers. We'll assume a few things first. Each title would be on BD50, there would be 3 Dolby Digital 5.1 @ 640kbps tracks, 1 Dolby TrueHD 5.1 track, and no extras on the disc with the feature. Also, LOA would be a 16bit audio track and LOTR would be at 24bit.

LOA:
- ABR: 24-25Mbps
- PBR: 40Mbps

LOTR EE (ROTK):
- ABR: 18-19Mbps
- PBR: 39Mbps

If you drop each to a single lossless track, it'll jump about 2Mbps on the ABR and the PBR on LOTR would jump to 40Mbps.

Granted, this is all speculation. Each studio may have completely different thoughts on what the disc should contain. For instance, New Line would more than likely do DTS-MA on LOTR. My opinion, LOA is fine as it is and LOTR should be split across 2 BD50s. With that split though, I'd add PIP and 7.1 lossless to the feature.

Thanks for that information! That looks like a pretty unacceptable ABR for ROTK on one disc.

On an entirely unrelated subject, do you think there is any chance of Warner, on a very selective basis, redoing titles for BD that have already been released on both formats?

[Icemage]

2themax,

Thanks once again for your insights. The above post on the theoreticals behind LoA and RotK EE are particularly enlightening. I am surprised that the ABR on the BD-50 of RotK EE ends up being so low; I assume those numbers are including things like encoding overhead and allowing for some real world considerations like space for menus, et. al.?

I have a question regarding the two lossless audio codecs. It's been said (by Amir Majidimehr, former VP of Microsoft) that Dolby TrueHD requires a higher audio peak bitrate (PBR) than DTS-HD MA at a similar bit depth.

Can you shed any light on whether this is true, and if it is, how much of a discrepancy there really is?

I suppose the real question I'm asking in my roundabout way is, on a "typical" encode, how much of the 48 Mbps Blu-ray max bandwidth do you have to reserve for a TrueHD 24 bit 5.1 audio track versus a similar 24 bit DTS-HD MA 5.1 audio track?

Moreover, would this impact the encoding on Blu-ray in any way, since there is theoretically 8Mbps of overhead that can be dedicated to audio?

[dialog_gvf]

Originally Posted by 2themax

LOA:
- ABR: 24-25Mbps
- PBR: 40Mbps

LOTR EE (ROTK):
- ABR: 18-19Mbps
- PBR: 39Mbps

If you drop each to a single lossless track, it'll jump about 2Mbps on the ABR and the PBR on LOTR would jump to 40Mbps.

Granted, this is all speculation. Each studio may have completely different thoughts on what the disc should contain. For instance, New Line would more than likely do DTS-MA on LOTR. My opinion, LOA is fine as it is and LOTR should be split across 2 BD50s. With that split though, I'd add PIP and 7.1 lossless to the feature.

There is a difference between what COULD be done and what SHOULD be done.

Richard Casey has said he believes the sweet spot is currently between 24-26Mbps ABR for VC-1/AVC. So, LOA would be nicely in today's sweet spot, but ROTK-EE well below it.

Is this a problem? Today, possibly. But how about when ROTK-EE is released? Will the encoders have improved to the point where 18-19Mbps ABR is the sweet spot (beyond which there are serious diminishing returns for increased ABR on the PQ).

This ignores other issues, like the amount of effort needed by the compressionist to deal with segment re-encodes. With a title like LOTR, I think we can assume that whatever effort is reasonable is likely to be justifiable.

Gary

[patrick99]

Originally Posted by dialog_gvf

Richard Casey has said he believes the sweet spot is currently between 24-26Mbps ABR for VC-1/AVC. So, LOA would be nicely in today's sweet spot, but ROTK-EE well below it.



Gary

Amir has said the same thing, I believe. Does that have an effect on how we view this opinion?

[DaViD Boulet]

Richard Casey has said he believes the sweet spot is currently between 24-26Mbps ABR for VC-1/AVC. So, LOA would be nicely in today's sweet spot, but ROTK-EE well below it.

Is this a problem? Today, possibly. But how about when ROTK-EE is released? Will the encoders have improved to the point where 18-19Mbps ABR is the sweet spot (beyond which there are serious diminishing returns for increased ABR on the PQ).

This ignores other issues, like the amount of effort needed by the compressionist to deal with segment re-encodes. With a title like LOTR, I think we can assume that whatever effort is reasonable is likely to be justifiable.

Great point. LOTR is not coming to BD today; probably a few years out.

Amir has said the same thing, I believe. Does that have an effect on how we view this opinion?

The principle of improving compression over time is true.

Amir quoted much lower numbers: Amir's starting point for "sweet spot" right NOW was already below where realistically might be 5 years out with Gary's prediction... and Amir's final numbers for a mature VC-1 codec were pushing downward towards SD DVD levels... probalby as a pre-justifiction for downloading bandwidth requirements. Indeed, most of MS's VC-1 compressions on WB titles maintain an ABR below 18 mbps. This isn't to say that they are transparent, but rather to illustrate what MS (Amir) want to suggest is transparent.

[patrick99]

Originally Posted by DaViD Boulet

Amir quoted much lower numbers: Amir's starting point for "sweet spot" right NOW was already below where realistically might be 5 years out with Gary's prediction... and his final numbers for a mature VC-1 codec were pushing downward towards SD DVD levels... probalby as a pre-justifiction for downloading bandwidth requirements. Indeed, most of MS's VC-1 compressions maintain an ABR below 18 mbps.

I thought that fairly recently (post-retirement) he had been citing mid-20's as the "sweet spot."

[Rob Tomlin]

Originally Posted by patrick99

I thought that fairly recently (post-retirement) he had been citing mid-20's as the "sweet spot."

He's been all over the map. I believe he also said that they were getting superb results at 15Mbps avg, and that with further improvements they expected that number to go even lower (to which many here asked why have HD DVD or Blu-ray at all, just use regular DVD if they could really get top quality at rates less than 15).

[DaViD Boulet]

I thought that fairly recently (post-retirement) he had been citing mid-20's as the "sweet spot."

If he did I appologise. I certainly remember him defending many WB VC-1 compressed titles as residing well within the 'sweet spot' of the codec in the past. And If Amir did change his mind later to accomodate a more realistic bit-rate, then his comment is no longer one to impune credibility along those lines (ie, the correct number doesn't now become incorrect just because Amir finally quotes it).

Of course, this leaves out the additional issue of the added time/cost to apply lower-bit-rate compression transparently. However, as Gary stated with LOTR, I'd expect a premiere title to get the silk-glove treatment with compression to ensure transparency.

[patrick99]

Originally Posted by DaViD Boulet

If he did I appologise. I certainly remember him defending many WB VC-1 compressed titles as residing well within the 'sweet spot' of the codec in the past. And If Amir did change his mind later to accomodate a more realistic bit-rate, then his comment is no longer one to impune credibility along those lines (ie, the correct number doesn't now become incorrect just because Amir finally quotes it).

Of course, this leaves out the additional issue of the added time/cost to apply lower-bit-rate compression transparently. However, as Gary stated with LOTR, I'd expect a premiere title to get the silk-glove treatment with compression to ensure transparency.

Based on my own personal viewing experience, somewhere in the 30's is much more of a sweet spot than mid 20's, and I believe that 2themax earlier in this thread agreed that increasing the bitrate from mid 20's to mid 30's could result in a meaningful PQ improvement where the quality of the source material was good.

[2themax]

Originally Posted by patrick99

On an entirely unrelated subject, do you think there is any chance of Warner, on a very selective basis, redoing titles for BD that have already been released on both formats?

I would say probably not. Most of their titles are well done even given the lower bitrates. Also, the market isn't all that big yet. It might not make sense from a business standpoint to invest the money for recompression.

[phloyd]

Originally Posted by Mr_Bester

Thanks for joining up.

I have several 1280x1080 HD ty files(.ts). Can you think of any software that will do a decent job going to 1440x1080 or 1920x1080 so I can finally see some Pulp Fiction in HD? I have tried Speededit, Premeire CS2 and AE CS2. Both Adobe choke on it, and speededit is more for editing(obviously). We will soon be upgrading to CS3, but if you have a better direction for roughly the same $$ that would be great. (disclaimer, We=work owns the software and HD ty=personal I recorded on D* HDTivo and want to watch through the PS3 since my HDTivo died)

It is possible to reflag the data as 1440 to get through the authoring process and then flag it back to 1280 afterwards.

I will warn you though that not all players do the right thing with this 'illegal' column count. The PS3 specifically scales it strangely last time I checked.

So you are probably going to want to recode to a supported resolution sadly... for best compatibility.

[2themax]

Originally Posted by Icemage

2themax,

Thanks once again for your insights. The above post on the theoreticals behind LoA and RotK EE are particularly enlightening. I am surprised that the ABR on the BD-50 of RotK EE ends up being so low; I assume those numbers are including things like encoding overhead and allowing for some real world considerations like space for menus, et. al.?

Yes that does take into account room for opening logos and menus, but not all that much. The idea on titles this long would be to give every available bit on the disc to the feature.

I have a question regarding the two lossless audio codecs. It's been said (by Amir Majidimehr, former VP of Microsoft) that Dolby TrueHD requires a higher audio peak bitrate (PBR) than DTS-HD MA at a similar bit depth.

Can you shed any light on whether this is true, and if it is, how much of a discrepancy there really is?

There is a slightly higher peak for Dolby TrueHD over DTS-MA. That's also factoring in core audios for both. From what I've observed, it's usually a small difference though. Dolby TrueHD may spike 500-600kbps higher than DTS-MA. When you have the bandwidth that we do on Blu-ray, it's hardly a factor.

I suppose the real question I'm asking in my roundabout way is, on a "typical" encode, how much of the 48 Mbps Blu-ray max bandwidth do you have to reserve for a Dolby TrueHD 24 bit 5.1 audio track versus a similar 24 bit DTS-HD MA 5.1 audio track?

Moreover, would this impact the encoding on Blu-ray in any way, since there is theoretically 8Mbps of overhead that can be dedicated to audio?

The most recent test I do was on a music title. The PCM was at 5.1 24bit/48kHz, which peaks at 6.912Mbps. The peaks for Dolby TrueHD and DTS-MA were roughly 6.1Mbps and 5.6Mbps respectively. With any one of the 3 audio bitrates, the video would still be peaking at 40Mbps. It would, however, effect the ABR of the video slightly.

[phloyd]

Just adding another reference point for compression:

Transformers on HD DVD has an average bitrate of ~20.5 Mbps.

So while 18-19 might seem low for LotR, with enough attention it is probably adequate. Though I firmly believe that more is more when it comes to encoding bitrate.

You can guaranty also that New Line will want DTS Master Audio 7.1 on that release.

[PeteS]

Welcome 2themax , I work for a custom video co. (making one-off and corporate DVDs and BDs) and have really appreciated your insights here. Thank you.

I wonder if you've had a chance to work with any HDV source material (for say, cast interviews or such). I understand the resolution issues and compression issues with fast motion on HDV but what's your impression of its color fidelity and overall suitability for non-title Blu-ray jobs.

[Icemage]

Originally Posted by 2themax

Yes that does take into account room for opening logos and menus, but not all that much. The idea on titles this long would be to give every available bit on the disc to the feature.

There is a slightly higher peak for Dolby TrueHD over DTS-MA. That's also factoring in core audios for both. From what I've observed, it's usually a small difference though. Dolby TrueHD may spike 500-600kbps higher than DTS-MA. When you have the bandwidth that we do on Blu-ray, it's hardly a factor.

I see! Much thanks for the clarification. I've learned something new today!

The most recent test I do was on a music title. The PCM was at 5.1 24bit/48kHz, which peaks at 6.912Mbps. The peaks for Dolby TrueHD and DTS-MA were roughly 6.1Mbps and 5.6Mbps respectively. With any one of the 3 audio bitrates, the video would still be peaking at 40Mbps. It would, however, affect the ABR of the video slightly.

Can you expand more on what the different effects on video ABR would be?

The way I've been led to believe, as long as the total audio streams total less than 8Mbps, then the 40Mbps peak is safe in all instances if we're just talking about bandwidth usage and had infinite storage capacity.

How, then, does the video ABR decrease based on the audio codec used in this example? Is it because of capacity issues (i.e. PCM 5.1 24/48 eats up a lot more space, and therefore less capacity can be allocated, making the max sustainable ABR lower?).

Is there a piece of the puzzle that I'm missing somewhere, or is the video ABR difference you mentioned above simply due to storage capacity limitation changes based on the space consumed by the audio?

[patrick99]

Originally Posted by phloyd

Just adding another reference point for compression:

Transformers on HD DVD has an average bitrate of ~20.5 Mbps.

So while 18-19 might seem low for LotR, with enough attention it is probably adequate. Though I firmly believe that more is more when it comes to encoding bitrate.

You can guaranty also that New Line will want DTS Master Audio 7.1 on that release.

I would not take Transformers on HD DVD as any sort of example of what we want to see. I was not impressed with the PQ, and apparently Michael Bay wasn't either.

[patrick99]

Originally Posted by 2themax

I would say probably not. Most of their titles are well done even given the lower bitrates. Also, the market isn't all that big yet. It might not make sense from a business standpoint to invest the money for recompression.

Sorry to hear that. The title I would MOST like to see redone with maxed-out bitrates is 2001. Not that it looked bad, but I just suspect it could look better.

[hanser]

Hello,

I made some suggestions in paidgeek´s thread, but some are I think authoring related, so I post those here, too. I would be interested to hear your comments.


- Since most players still take a long time to load Java menues, would it be possible to include at the beginning of Java titles a choice between the full Java menue loading and a "movie only" option which circumvents the Java with all the extras. It would be extremly helpful if you just want to watch the movie, which is mostly the case in real life. Ideally then the disc would be like a Warner BD: Logo, maybe some FBI thingy if necessary, and the movie starts without further ado.

- BD-Java titles start from the beginning after one has pressed "Stop", while other titles just resume with play. If technically possible it would be nice, that also Java titles could resume after "Stop".

- I like it when the scenes menue has a scrolling band of small pictures, but it would be still better, if it would start at the scene you are just watching. E.G if I go the scenes menu in the middle of the movie, because I am looking for a scene further at the end, I nevertheless start with the first scene (at least those titles on which I tried) and have to scroll through all scenes which takes some time and work. Could the player be instructed to start at the current scene?

- I do not know if it is only with my Sharp player, but I can´t chose chapters via the numbers on the remote. If it is a general BD thing, it would be nice to have this function.

- User prohibitions. Is it really necessary to forbid going "next" for exemple while the menu is building up? I would be nice if this restriction would not be used any more, it is really bothersome, if you just want to watch the movie.


- When I watch extras I can´t access the menu. I have to skip forward until the extra is finished, then it reverts to the movie. It would be nice to access to the menu at all times during watching extras, so you could directly switch to another extra.

[2themax]

Originally Posted by PeteS

Welcome 2themax , I work for a custom video co. (making one-off and corporate DVDs and BDs) and have really appreciated your insights here. Thank you.

I wonder if you've had a chance to work with any HDV source material (for say, cast interviews or such). I understand the resolution issues and compression issues with fast motion on HDV but what's your impression of its color fidelity and overall suitability for non-title Blu-ray jobs.

I haven't had the chance to work with any HDV source material yet.