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Topic: dcp vs blu ray

Marcel Birgelen
Film God

Posts: 3357
From: Maastricht, Limburg, Netherlands
Registered: Feb 2012

posted 07-08-2013 01:11 AM

quote:
By the way, what the hell is up with Warner Bros? Why do they compress more? Do they feel by creating smaller DCPs that they are saving on shipping charges or something? "Well our movie is several gigabytes smaller than other movies of comparable length so it should weigh less and cost less to ship!"

Less bits is less weight, didn't you know? [Smile]

. But, maybe they try to save on bandwidth cost here for stuff like satellite distribution? Or maybe they're just ignorant?

quote: Joe Redifer
It's like I'm at a party and strange people are pushing new drugs I've never heard of to everyone.

Want some? [Razz]

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Bobby Henderson
"Ask me about Trajan."

Posts: 10973
From: Lawton, OK, USA
Registered: Apr 2001

posted 07-08-2013 11:19 AM

quote: Marcel Birgelen
I guess that Bobby was pointing at the fact that for example the maximum bitrate of the Dolby Digital AC-3 stream for DVD content is 448 kbit/s, whereas the 35mm version is stuck at a maximum of 320 kbit/s.

Let's not forget Dolby Digital tracks on Blu-ray are typically encoded at the maximum bit rate of 640kb/s. I can't remember if the dead HD-DVD format treated Dolby Digital the same way or dropped it to 448kb/s. The Dolby Digital Plus format could run at higher bit rates (up to 6.1Mb/s) as well as the low bit rates typical of Dolby Digital. Dolby TrueHD is lossless; IIRC it is derived from the Meridian Lossless Packing "MLP" format that was also used on the DVD Audio music format.

quote: Anhtu Vu
I can't speak for everyone but, YES, one can draw the line as to what format is acceptable for screening and that's exactly what i did when i became in charge of our cinema room. Only DCP, HDcam SR and MOV/MXF file are accepted. The files must follow our very strict technical requirement. We do NOT take DVD or BLuRay.

If you're going to turn up your nose at Blu-ray media why are you willing to accept .MOV or .MXF files? Video files in .MOV or .MXF can contain or be sourced from the very same kind of MPEG-4 AVC material commonly used on Blu-ray movie discs. If I shoot 1080p/24 video on my Canon 5D Mark II camera the MPEG-4 AVC encoded video file is stored in a .MOV wrapper. Additionally any .MOV file could be even more severely data compressed than the encode used on a Blu-ray. That's particularly true of something meant to be streamed across the Internet rather than distributed on a physical disc.

The primary reason why I would avoid Blu-ray disc use in a commercial theater booth comes down to the movie being difficult to cue and play quickly. Video compression levels on Blu-ray are typically more harsh and severe than what is used on DCP. But movies on DCP can be harshly compressed as well. The limitations in the still image based JPEG 2000 format don't allow file sizes to be squeezed down so much without costly image quality loss. So it's indeed possible for a 50GB movie on DCP to actually look worse than its AVC-based version on Blu-ray.

quote: Joe Redifer
By the way, what the hell is up with Warner Bros? Why do they compress more? Do they feel by creating smaller DCPs that they are saving on shipping charges or something?

My theory: it's an outdated "always do this in this way" policy handed down to employees from on high by some executive not bright enough in technical terms to know better.

Warner Bros. has been doing this low bit rate stuff since the 1990s. On DVD it was common for them to encode MPEG-2 SD video really low and encode the DD 5.1 tracks at 384kb/s while the other major studios were using higher video bit rates and DD 5.1 tracks at 448kb/s. WB has lots of BD-50 movie discs that would fit on a 30GB HD-DVD platter even though many of those movies were authored to BD years after the HD-DVD format died. In my early exposure to D-cinema I was used to seeing movie file sizes around 200GB. Then some WB movie comes in weighing only 60GB. I was left thinking "wtf, is that even possible?"

Satellite distribution is a good excuse for using smaller file sizes and maybe even true video compression formats like MPEG-4 AVC (hopefully at a higher bit rate at least typical of Blu-ray quality). But I think the encode-compression policy at Warner Bros. runs deeper than that. It seems like an ideology there: more compressed=better.

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Scott Jentsch
Phenomenal Film Handler

Posts: 1061
From: New Berlin, WI, USA
Registered: Apr 2003

posted 07-10-2013 03:37 PM

I did a bunch of research on this back in the day, which I posted on our site: Dolby Digital Sound on Blu-ray and HD DVD Explained

quote:
On DVD, Dolby Digital is limited to a bit rate of 448 kbps. Blu-ray is capable of transporting Dolby Digital at a bit rate of 640 kbps. (By comparison, Dolby Digital in movie theaters is limited to 320 kbps) On HD DVD, it is limited to a slightly higher bit rate of 504 kbps.

On Blu-ray, a Dolby Digital soundtrack is mandatory, while Dolby Digital Plus is optional. If a Blu-ray disc has a Dolby Digital Plus or Dolby TrueHD bitstream, there will also be a Dolby Digital track to ensure downward compatibility.

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