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This topic comprises 3 pages: 1 2 3
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Author
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Topic: dcp vs blu ray
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Jack Ondracek
Film God
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Posts: 2348
From: Port Orchard, WA, USA
Registered: Oct 2002
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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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Bobby Henderson
"Ask me about Trajan."
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Posts: 10973
From: Lawton, OK, USA
Registered: Apr 2001
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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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