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Topic: dcp vs blu ray

George Murray
Film Handler

Posts: 23
From: grand forks ND,
Registered: Jun 2012

posted 07-01-2013 08:12 AM

In terms of the quality of the content how much of a difference is there between blu ray and 2k dcp. Like if you put both contents on a 20 foot wide screen would you be able to tell a difference. I only ask because naturally you would assume that when a file goes from 130 gb to under 40 gb and much lower bit rates you would presume a significant loss in quality

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Martin McCaffery
Film God

Posts: 2481
From: Montgomery, AL
Registered: Jun 99

posted 07-01-2013 08:42 AM

Well, you'll certainly notice when the BluRay freezes up or starts stuttering [Wink]

Running BluRay this week and not happy.

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Scott Norwood
Film God

Posts: 8146
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99

posted 07-01-2013 08:44 AM

Doesn't matter to me. The DCP will (usually) work reliably and the Blu-Ray will not.

The real answer to the question is "it depends." You can make a DCP from a Blu-Ray, and the size will increase, but the quality will be no better than that of the original source material.

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Mike Blakesley
Film God

Posts: 12767
From: Forsyth, Montana
Registered: Jun 99

posted 07-01-2013 08:45 AM

We have a 30 foot screen here and it is downright amazing how good a Blu-ray looks. Even a regular DVD looks very good.

In my opinion the biggest difference is in the contrast. DCP has better darks. On a 20 foot screen I bet 99% of the audience won't know you're showing a Blu-ray unless you tell them, or unless something else gives it away, like an on-screen display caused by the player showing up.

On the dependability issue, I've probably played at least 30 Blu-rays and or DVDs, almost all for private viewings after regular shows are over for the day, and I have never had one freeze up or skip yet. I suppose my time is coming!

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George Murray
Film Handler

Posts: 23
From: grand forks ND,
Registered: Jun 2012

posted 07-01-2013 08:50 AM

Also why are the file sizes so much smaller than the dcp?

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Bobby Henderson
"Ask me about Trajan."

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

posted 07-01-2013 10:20 AM

On average the video from a DCP should look noticeably better than the same movie on Blu-ray. But that all depends on certain good practices being in place when the video is encoded to the DCP and Blu-ray platforms.

You also have to consider color bit depth on the DCP imagery versus that of the Blu-ray. BD is able to support "deep color" but I don't know of any titles that have actually used it.

quote: George Murray
Also why are the file sizes so much smaller than the dcp?

Video on Blu-ray is typically encoded in MPEG-4 AVC format. Some videos are encoded in Microsoft's VC1 format. A few use the less efficient MPEG-2 format.

Video on DCP really isn't video at all. It is a container holding many thousands of JPEG2000 compressed still images. This method doesn't allow for the various kinds of inter-frame compression tricks and techniques which are used in AVC, VC1 and MPEG-2 video streams. The imagery is also supposed to contain a limited number of transform tile blocks per image (only 1 in the master and hopefully no more than 3 in the DCP); home video formats can use dozens of transform tile blocks. Just make the picture macro-block to hell for all the viewer cares, right?

Anyway, the JPEG2000 format on DCP does not allow for compression levels anywhere near as severe as the video compression formats for home video & broadcast.

I'm accustomed to seeing a 2 hour movie on DCP have a file size of 150GB-200GB or even bigger. When I see a 2 hour movie on DCP drop down to the 50GB-75GB level I wonder just how much has been compromised in squeezing the imagery down to that level. Such a movie on DCP might not hold up quite so well to a side by side comparison with its Blu-ray counterpart. Alas, a studio that uses an unusually severe amount of compression in its DCP (such as WB) also will tend to use unusually severe amounts on compression on the Blu-ray -making a 2 hour movie not even fill up one layer of a BD-50 disc.

quote: Scott Norwood
Doesn't matter to me. The DCP will (usually) work reliably and the Blu-Ray will not.

What kind of Blu-ray player is being used?

I'm still playing movies using my Sony Playstation 3 "slim" model. I haven't had any problems with it. However, I guess it's not the sort of device that's geared for a movie theater booth.

Lots of "standalone" BD players are trash. They load discs very slowly. They exhibit all kinds of odd behaviors. My girlfriend's Samsung BD player emits this loud beep sound over the TV speakers whenever the disc is stopped, scanned in fast forward or reverse. It's very irritating. I updated the firmware and to no avail that beep is still there.

I hear Oppo makes a hell of a great Blu-ray player. It just hurts to spend $500 on a Blu-ray player.

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Anhtu Vu
Film Handler

Posts: 98
From: Montreal, Quebec, Canada
Registered: Jun 2013

posted 07-01-2013 12:34 PM

There's no comparison...DCP of the same film will look/sound much better than its Bluray version.

Bluray video encoding is based on H264/Mpeg4 part 10 or AVC with average bandwith encoded in VBR between 12-32 Mbits/s versus 250 Mbits for DCP. This is without taking into account the quality of the Codec itself, H264 vs Jpeg 2000...again, no comparison J2000 is a much better codec.

Also let's not forget about sound quality...full 24 bits uncompressed @ 192 Khz for DCP vs AC3, DolbyTrue HD or DTS Master audio for BluRay. Technically the two latter are ''lossless'' but trust me, as a mixer, i definitely notice a difference between my original mix and the DTS Master or DolbyTrue HD stream decoded.

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Marco Giustini
Film God

Posts: 2713
From: Reading, UK
Registered: Nov 2007

posted 07-01-2013 03:40 PM

Mike,

When it comes to DCP the standard is very tight, when it comes to alternative content it's much more loose.
You possibly have the wrong video levels set. If you search for AVS-HD you can run the test patterns and check your black and white levels. I found they go with the player sometimes. I bet your black is not actually black! [Smile]

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Mike Blakesley
Film God

Posts: 12767
From: Forsyth, Montana
Registered: Jun 99

posted 07-01-2013 06:09 PM

quote: Anhtu Vu
Bluray video encoding is based on H264/Mpeg4 part 10 or AVC with average bandwith encoded in VBR between 12-32 Mbits/s versus 250 Mbits for DCP. This is without taking into account the quality of the Codec itself, H264 vs Jpeg 2000...again, no comparison J2000 is a much better codec.

All of that stuff might be very true, but to my own 34-year-veteran-of-the-industry eyes, it looks about 99% as good as DCP from the seats, at least when you sit a reasonable distance from the screen.

I haven't ever had a chance watch the same movie on a DCP and a Bly-Ray one after another to make an A-B comparison, but I stand by my earlier statement that all but the most knowledgable viewers would likely never know the difference.

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Anhtu Vu
Film Handler

Posts: 98
From: Montreal, Quebec, Canada
Registered: Jun 2013

posted 07-01-2013 08:40 PM

quote: Mike Blakesley
All of that stuff might be very true, but to my own 34-year-veteran-of-the-industry eyes, it looks about 99% as good as DCP from the seats, at least when you sit a reasonable distance from the screen.

I haven't ever had a chance watch the same movie on a DCP and a Bly-Ray one after another to make an A-B comparison, but I stand by my earlier statement that all but the most knowledgable viewers would likely never know the difference.

To each his own i guess. I work as an on line editor and mixer for the film and broadcast industry. We also do Blu ray and DCP authoring for independent and feature film.
From my experience and also feedback from all of our clients, the difference between a Bluray and DCP of the same film is night and day....no comparison. Since we are responsible for the entire post-production chain of most films that come through our facility, we get to compare and see this side by side on a weekly basis....again no comparison.

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Mike Blakesley
Film God

Posts: 12767
From: Forsyth, Montana
Registered: Jun 99

posted 07-01-2013 09:03 PM

Maybe it depends on where you are doing the comparing. Technicians in controlled environments are in a situation quite different from a commercial theater. Also the difference between 2K and 4K theatrical projection might make the contrast more pronounced (we have 2K here and I've never seen 4K except at CinemaCon).

I'm not doubting your word, and probably with your trained eyes you could spot the differences in a nanosecond; but what I'm saying is the general public (which is who does about 99.999% of the movie watching) would not be able to tell.

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Jack Ondracek
Film God

Posts: 2348
From: Port Orchard, WA, USA
Registered: Oct 2002

posted 07-01-2013 10:17 PM

I'm with Mike on this.

As a broadcast engineer, I can listen to a radio station and tell you most of the things they're doing to squish, clip, press and form their audio into their licensed bandwidth. I'm not sure I could live in New York, given how aggressively broadcasters there adulterate their audio. Amazingly to me, some of the worst offenders have high ratings.

I've done DCP vs BluRay comparisons on my 86-foot drive-in screen. Yes, I can tell the difference. Mainly, colors are not as vibrant and black levels aren't so much so. It looks a little like a TV with the contrast turned up too much. To me, the audio mixes are less dynamic than what I normally hear on a DCP. That probably makes sense, given the home environment the bluray is intended to play in.

Can an engineer, who works with theatrical creation hear and see the difference? He'd better. That would be expected. Does this mean anything to the average viewer? Maybe, to some, but probably not to someone who considers bluray acceptable in any environment.

Would I run a bluray if I couldn't get a DCP? I guess, if I had to. The players don't scare me. I have a Sony here, and it's worked fine. I'd much prefer to put the content in my server though, so it can be run normally in a playlist with the rest of the content and control macros I use during a normal evening. For that, I'll probably wait until I get the chance to play with some of the conversion software out there.

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Anhtu Vu
Film Handler

Posts: 98
From: Montreal, Quebec, Canada
Registered: Jun 2013

posted 07-02-2013 02:03 AM

Anybody from our concierge to our secretary could see the difference between the final DPX sequence vs the Jpeg2000 encoded sequence (for DCP) vs the Bluray version of the same film being projected in our cinema room. My 15 year old girl tells me every time the BLuray looks like a youtube video compare to the original DPX sequence [Smile]

ok, maybe she exaggerate a tiny bit, but you get the point !

My take on this whole debate......most ''average'' movie goers have much better eyes and hearing than you expect. The question one should ask himself is not wether they can see the difference but wether they care enough to pay more for the best possible screening and, as a venue, what's the lowest standard are you willing to accept.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 07-02-2013 06:34 AM

Personally, I find the difference between a BluRay image and a DCP image to be rather large. It isn't really a close call. I've found that as one goes beyond a 20-foot wide screen the differences grow geometrically.

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Bobby Henderson
"Ask me about Trajan."

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

posted 07-02-2013 09:37 AM

quote:
Bluray video encoding is based on H264/Mpeg4 part 10 or AVC with average bandwidth encoded in VBR between 12-32 Mbits/s versus 250 Mbits for DCP. This is without taking into account the quality of the Codec itself, H264 vs Jpeg 2000...again, no comparison J2000 is a much better codec.

Anhtu, you're comparing apples to oranges. You're claiming JPEG 2000 (a still image compression codec) to MPEG-4 AVC (a video compression codec) and claiming it's better. That's not really true since the two compression formats serve different purposes.

You could, in theory, encode a movie in JPEG 2000 and use compression levels severe enough to fit it onto a Blu-ray disc. But since JPEG 2000 doesn't support a variety of video compression features and can only work on one discrete image at a time it's going to be far less efficient at encoding/compressing a movie than MPEG-4 AVC.

You're oversimplifying what can be encoded onto Blu-ray. As I said earlier MPEG-2, MPEG-4 AVC and Microsoft VC-1 video formats can be used. The video imagery can be encoded in various resolutions and frame rates with any of them being interlaced or progressive scan. Bit rates vary wildly too. They can run at the compression levels as horribly severe as an iTunes "HD" streaming video: 720p at bit rates lower than a halfway decent SD DVD. Or they can run at bit rates up to 50 million bits per second.

The "video" on DCPs are not all encoded at the same compression levels either. Just look at the huge file size differences between one DCP to another. One movie may be over 200GB in size while another of the same duration may only be 50GB.

The 250 million bit per second data rate you mentioned is the peak, maximum rate allowed. JPEG 2000 imagery can and does run well under that. Also, that 250Mb/sec peak limit applies to both 2K and 4K video. So if a studio quadruples the pixel count and outputs the movie in 4K resolution they're also going to have to increase compression levels. And they do.

quote: Anhtu Vu
Also let's not forget about sound quality...full 24 bits uncompressed @ 192 Khz for DCP vs AC3, DolbyTrue HD or DTS Master audio for BluRay. Technically the two latter are ''lossless'' but trust me, as a mixer, i definitely notice a difference between my original mix and the DTS Master or DolbyTrue HD stream decoded.

That's inaccurate. For one thing Blu-ray supports LPCM high resolution audio (24-bit 96kHz surround and 24-bit 192kHz stereo). The DTS-HD and Dolby TrueHD lossless formats also support those resolution levels.

While DCP may be able to support Linear PCM audio at high resolutions the reality of what is actually being copied to DCP virtual prints is different.

Virtually all movies on DCP have Linear PCM audio set at 24-bit 48kHz resolution or 20-bit 48kHz resolution, either in 5.1 or 7.1 channel layouts. 16-bit audio can be used too. Can anyone actually name a DCP that contained audio at a higher sample rate than 48kHz, such as 24-bit 96kHz?

24-bit 192kHz is a very tricky audio format that is very rarely ever used. All playback implementations I've seen of it have been strictly 2.0 channel stereo. For 5.1/7.1 surround the resolution tops out at 24-bit 96kHz. I've read articles about 24-bit 192kHz audio yielding inferior results to 24-bit 96kHz due to technology limitations in audio playback hardware.

Recorded/encoded audio is an area where home theater has had a leg up on commercial theaters for a long time. How the audio is played in a home listening environment is another matter, but the recordings on disc have often been more elaborate and/or higher in resolution than what the commercial movie theaters have been getting. This has been true on the Blu-ray format and it goes back to DVD.

Dolby Digital operated at higher bit rates in its home version versus that of the theatrical format. There were a lot more movies released with Surround EX style tracks on DVD than were released in commercial movie theaters. Blu-ray was doing quad-surround 7.1 audio years before d-cinema started supporting it. Blu-ray has also been taking over in the high end audio niche market. Lots of HD concert videos have been released on Blu-ray with 24/96 audio. A few movies have been released on Blu-ray with the same kind of high resolution audio. Some music acts such as Neil Young and Nine Inch Nails have released BD Audio discs with high resolution audio.

Dolby Atmos is the first audio format in 20 years that's actually tried to put commercial movie theaters on a level above home theater. But the rollout for Atmos is going painfully slow. The process is really expensive. And the marketing effort for Atmos hasn't been worth a damn.

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