Film-Tech Forum ARCHIVE: What feedza DLP?

This is topic What feedza DLP? in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=16;t=000161

Posted by Mark Ogden (Member # 43) on 08-16-2001, 09:56 AM:

Took the Little Lady to see "Planet of the Apes" in DLP the other day and wound up having the "it's not film but it's not really video either" conversation with her (her reply: "Whatever. Where do you wanna eat?). And I realized I'm missing a point of information: what is the format of the feed coming out of the video server and feeding the projector? RGB? YUV? Something else entirely?

Thanks!

Posted by John Pytlak (Member # 331) on 08-16-2001, 10:38 AM:

From the TI website, info for "Toy Story 2":

"Pixel Data:
The image data is stored at 10 bits/component (Y/Cb/Cr) in 4:2:2 format. Since the
DMD™ is a linear display device (i.e., no gamma characteristic as does a CRT), the data is
gamma corrected and converted to linear RGB data. Each DMD™ displays 14 bits/color,
linear data."

"Storage:
The picture information was compressed and stored using a QuBit compression system
produced by QuVis of Topeka, KS. The QuBit uses proprietary wavelet compression
technology with a user selectable SNR. This unit compressed the movie to an average
data rate of 37 Mbits/sec for a total of 32 Gbytes of data for the entire presentation
(including trailers). The compressed data is stored on four computer HD drives with a
total capacity of 72 Gbytes. As an entire digital cinema production, distribution, and
exhibition infrastructure develops, other technologies will likely be tested."

PostIndustry magazine said:
"Planet of the Apes" will be digitally
projected on Aug. 10 in a special
screening at the AMC Empire 25 in
Manhattan. Lucasfilm's THX division
supervised the creation of the digital
master and handled the on-site
technical preparations for both the
sound and projection. Playback will
come from an Avica FilmStore digital
cinema player while projection will be
handled via Texas Instruments' DLP
Cinema projector."

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

Posted by Jonathan Haglund (Member # 807) on 08-16-2001, 07:03 PM:

A total of 72 GB??

Why then is there an issue with storage for large movies when one can go to the store and purchase (1) 80GB hard drive? It is a very cheap component, yet the designers ignore the availabilty of such things and sacrifice the amount of content (extra trailers) and possibly the quality?

Posted by Gordon McLeod (Member # 33) on 08-16-2001, 07:37 PM:

Becauase a standard hard drive doesn't have the duty cycle required
The storage is done in a raid array as well.

Posted by Mark Ogden (Member # 43) on 08-16-2001, 08:14 PM:

Er. . .lemee see if I understand this correctly. The movie is stored as component at 4:2:2, but is somehow transcoded to RGB for gamma correction before playback? Is there a special gamma curve characteristic that must be obesrved for the DMDs to faithfully reproduce color (outside of the normal gamma range that occurs in film and/or video anyway)?

Posted by John Pytlak (Member # 331) on 08-17-2001, 08:38 AM:

Jonathan asked: "Why then is there an issue with storage for large movies when one can go to the store and purchase (1) 80GB hard drive? It is a very cheap component, yet the designers ignore the availabilty of such things and sacrifice the amount of content (extra trailers) and possibly the quality?"

The TI website specifies "an average data rate of 37 Mbits/sec" which is pretty hefty, even for the 1280 x 1024 pixels of current displays. Future higher-resolution systems may require even higher data rates.

Posted by Pete Naples (Member # 761) on 08-17-2001, 02:43 PM:

Mark,

Each DLP is colour calibrated at installation, for light output and colour balance. Therefore no correction is required within the playback system. However it is possible (and has been utilised in recent DLP release) that a non standard colour look up may be required, this information would be included in the QuBis files for a given presentation. As to what actually comes out of the server; it's as described above, the Barco D CineStar has the option of what is basically an input switcher/format convertor, which would, for example, allow you to feed composite video in to your DLP, should you so desire!

Posted by Joe Redifer (Member # 3) on 08-17-2001, 05:03 PM:

John, do you mean 37 megaBITs or 37 megaBYTES? 37 mbits is less than 5 megaBYTES per second, which is nothing. My DV camcorder records at about 5 megabytes per second, I believe (or somewhere in that neighborhood). A 7200 rpm IDE drive can handle speeds much higher than that constantly with ease. Actually I think I even have a 5400 rpm drive (IDE) that also easily handles DV footage, which appears to be more data than DLP.

It's amazing to think that my camcorder has more information than DLP.

Posted by Scott Norwood (Member # 30) on 08-17-2001, 05:40 PM:

FYI, the 80-gig drives that they sell at Best Buy are _not_ the same thing as server-grade storage, which depends upon having data "striped" across multiple drives in a RAID configuration with extra drives for redundancy and automated failover in the event of a head crash or other drive failure.

Just last year, my employer purchased 200 gigs of storage (a bunch of drives in a Sun A1000 RAID array) for about $20k. This doesn't include the additional costs of labor to install it or of the hardware and media necessary to back it up.

Storage is _not_ cheap, contrary to popular (?) belief these days...

Posted by John Schulien (Member # 215) on 08-17-2001, 06:08 PM:

Those Sun drives are SCSI drives, which are way, way more expensive then IDE drives.

The difference is that they are faster (10,000 RPM vs 7200 or 5400 RPM), and you can have up to 15 drives on a single bus, as opposed to two on an IDE bus.

I was curious just how fast I could extract data out of my own hard drive. The fastest way you can access a hard drive is to read consecutive sectors -- one after another. This minimizes the amount of head motion on the hard drive.

I'm running Linux on my desktop machine, so I have the ability to easily run timing tests. Here's my simple test:

$ dd if=/dev/hda3 of=/dev/null bs=1048576

This is the basic data copy command. I'm telling the computer to read from a 1.4GByte partition, and "copy" the data to /dev/null, in other words, read the data, then throw it away.

The operation completed in 324 seconds.

So, 1.4GBytes / 324 seconds = 4.8 MBytes/Sec = 38 MBits/Sec

All I have is a boring, old 5400 RPM IDE drive. Even with the most basic, inexpensive hard drive, I was able to sustain enough continuous bandwidth to support this application. And this is on an obsolete computer! If I had a 7200 RPM drive, or a more modern chipset, or a RAID chipset, the results would only be better.

So yes, I believe that it would be entirely possible to use commodity PC hardware for DLP storage. I doubt you could use windows to control the hard drive thought ... it would probably require either Linux, some other Unix, or a real-time operating system like Be. It would also require that the movie data be placed linearly on the drive, but that's entirely feasible.

Posted by Joe Redifer (Member # 3) on 08-17-2001, 06:28 PM:

I haven't heard about BeOS for awhile. Doesn't that only run on Mac hardware?

I agree that it would easily be possible to run the DLP data off of consumer grade hardware, but that's probably not what should be done. Of course, it would have to be a really crappy hard drive to poop out on reading DLP movies constantly. It shouldn't be doing much (if any) writing, and the data should be linear, meaning the head movement should be minimized. A server grade HD would be MUCH more reliable in the long run obviously. But c'mon, do you seriously think that the industry WON'T go with the cheaper method?

Remember, money is more important than quality to the big-wigs.

I've owned several SCSI drives I've always hated them. What is up with this "termination" BS? Limits of ancient technology, I guess. SCSI has a faster bus than IDE, that's for sure, but there is just something about them that reminds me of piss poor quality. They're not as great as some people would have you believe. Firewire drives have proven to be faster (for me).

Posted by Jonathan Haglund (Member # 807) on 08-17-2001, 06:40 PM:

As far as duty cycle goes, belts last 6 months to a year. A basic hard drive in a Redunant Inexpensive Disk Array would last 3-5 years with normal theatre usage. An ATA/100 7200 rpm drive has a throughput of 100 megabits per second, which gives 12.5 megabytes per second. So obviously a SCSI raid is needed. I'm not trying to pick a technology fight with TI, mind you, it just seems they're putting a some "gee-wiz" technology in to the system that so many geeks do in production environments simply because they want to play with the new technology or expensive toys. </rant>

BTW, I was really happy to hear about the system that Kodak is developing for DLP. Its seems so obvious that that's how DLP needs to be managed.
http://www.kodak.com/US/en/motion/digital/cineOpSys.shtml

Posted by Scott Norwood (Member # 30) on 08-17-2001, 06:47 PM:

I'm a SCSI snob myself (IDE sucks...), and it is pretty much necessary for any sort of "serious" application, since RAID controllers and tape drives all use SCSI interfaces. (Yes I know that there are some wacky IDE-based RAID controllers and, no, I don't think it's a good idea.)

BTW, my personal experience is that SCSI seems to have fewer problems than IDE and it's simpler to understand: each device needs its own ID number and the chain must be terminated. That's easier than IDE, where each chain can only contain two devices, each of which is either set up as "single," "master," or "slave."

Posted by Joe Redifer (Member # 3) on 08-17-2001, 08:02 PM:

I've never had any problems with IDE drives. And I do a massive amount of video editing. The drives are always quick enough and haven't broken down/hiccuped at all. There has never been an instance where the drive has seemed too slow. I will be the first to admit that IDE is very limiting, with only two devices allowed per bus. When I had SCSI (1 drive, 1 device) it just seemed slow(er). I like Firewire. Hot pluggable. No need to set ID numbers. No termination. Don't need to plug 'em into a power source. 50 MBYTE per second transfer speeds. 63 connected devices simultaneously. BS factor = MUCH LESS any way you look at it.

RAID arrays kick ass, and as Scott pointed out are not cheap. However technology MUST advance, and SCSI will be obsolete someday, as will IDE and Firewire. Someday soon we will have massive drives more reliable than SCSI RAID arrays, and they'll be cheaper. Some techno geeks may think otherwise, but that'll mostly be because they'll want to have a platform to argue where they can feel superior to the common computer user.

Posted by Paul Konen (Member # 41) on 08-18-2001, 01:13 AM:

From the QuBit, the signal is High-Definition (HD) over standard coax cable. This is with the new QuBit system. The older systems has a different system that converts the output from the QuBit to HD with an external device.

The drives internally are SCSI and have 4 primary drives and 4 secondary drives that are mirror set.

Also, there are other systems being investigated as sources other than the QuVis QuBit.

Paul.