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Grain Issues


jijhh

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My computer's packed up so not at the moment, but I'll try and get one up in the future. I'm off to Prague tomorrow for six months so I'll have to figure out a new solution. Right now I've got a drive with my 1080p DVCPRO HD selects (and a backup) and my new MacBook Pro. I've played back and made a few edits on my laptop and it seems to be running fine. Could I just make a cut on this that I could then open on a more powerful machine for exporting to DVD? Is running the 1080p on my Macbook going to be too taxing or harmful in any way? I haven't tried anything beyond a few edits, but it seems to be working perfectly alright with realtime playback.

 

I also have never traveled with harddrives (Two Lacies, 160GB and 200GB), but I will be bringing them in my carry-on and nursing them like children. Is there anything regarding packing or airline security, i.e. x-rays, that I need to know about?

 

Thanks in advanced.

 

PS Just in case, anyone know any labs in Prague?

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My computer's packed up so not at the moment, but I'll try and get one up in the future. I'm off to Prague tomorrow for six months so I'll have to figure out a new solution. Right now I've got a drive with my 1080p DVCPRO HD selects (and a backup) and my new MacBook Pro. I've played back and made a few edits on my laptop and it seems to be running fine. Could I just make a cut on this that I could then open on a more powerful machine for exporting to DVD? Is running the 1080p on my Macbook going to be too taxing or harmful in any way? I haven't tried anything beyond a few edits, but it seems to be working perfectly alright with realtime playback.

 

I also have never traveled with harddrives (Two Lacies, 160GB and 200GB), but I will be bringing them in my carry-on and nursing them like children. Is there anything regarding packing or airline security, i.e. x-rays, that I need to know about?

 

Thanks in advanced.

 

PS Just in case, anyone know any labs in Prague?

 

A new macbook pro is more than capable of working with dvcprohd. The only place you may start to see some issues with playback is if you develop an intensly dense edit where the hard drive has to skip around a lot to play everything back in realtime. If you're working on an external 3.5" fullsize hard drive, you shouldn't have any issues.

 

About moving to a more powerful machine for dvd encoding....

I just got a new core2duo 2.33ghz 17" and I can say that without a doubt this machine equals and probably in most cases surpases the performace of my dual 2.7ghz g5 when it comes to cpu intensive stuff. I'm basing this observation on my experience with some pretty intense shake scripts I've worked with on both machines.

 

But yeah, when you get a chance, please try to post some frame grabs and note next to each the film stock, lens used, lens aperture, and remind us again which machine it was transferred on (if it was post works im assuming it was either a spirit or shadow).

 

DVCProHD is usually pretty difficult to confuse...what I mean by that is it's pretty difficult to feed material to a dvcprohd encoder that will make the compression puke and look nasty. Noise wouldn't usually be introduced by this compression...in video (like on a varicam) the noise comes from the imaging system.

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When you get settled in, can you email me a 15-second clip filmed with DVCProHD compression? I'm using HDV 25p and I want to compare them because HDV is higher resolution at 1440x1080 @ 25 Mbps but DVCProHD 1280x1080 uses less compression @ 50 Mbps. I can't find any agreement in comparisons for graininess, sharpness, etc. so I want to see for myself. Enjoy the beer!

Edited by Mark Simkiss
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  • 2 weeks later...

I checked the image and there is absolutely no noise in chroma channels. It is compressed jpeg but the noise is ZERO in the flat area on the center while the fine detail and film grain is preserved in some of the lower parts of the image, so Jpeg compression did not removed any serious noise. The noise is luma only. This is either not film grain or material that was heavily (and impressively well!) denoised in chroma channels only. But only in some parts of the image? Very unnatural.

 

If you can post an uncompressed image perhaps I could help. Film noise from boosting, sensor noise, noise from debayer issues and everything else has a specific recognisable pattern.

Edited by Panagiotis Grapsas
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This could be a case of grain aliasing. Film grain in some high speed films is very fine (at very high frequencies) and cannot be captured precisely in the low resolutions we use for scanning film for video. The part that cannot be captured aliases into lower frequencies. The noise gets fat and ugly and this phenomenon gets worse when we sample at lower resolutions. This can be fixed by optical filtering on input but the labs prefer to optimise for sharpness.

 

Some images from fast film contain lots of grain and should be filtered before any resolution reduction and sharpened afterwards in order to compensate, since optical filters are not steep enough and tend to soften the mid frequencies. On digital images that do not have much grain this is less critical and this is the reason most applications for video or photography skip the filtering step and let alias appear. Conversion to lower resolution formats like DV or DVCPROHD can magnify the problem.

 

There is an example on this page:

 

http://www.photoscientia.co.uk/Grain.htm

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