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Compression headache

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Owen RR
Compression headache
on Feb 28, 2007 at 12:13:41 pm

Hi,
Apologies for making my first post a technical problem but I'm having difficulties with what I suspect may be the finer points of m2v compression. I've read quite a few of the posts on this forum and tried to absorb as much info as possible but I'm still having difficulties, my problem is as follows. When trying to compress m2v's for my company's showreel or for client presentation I get alarmingly varied results. I've tried using mainconcept as a standalone and in Premiere, also Sorenson squeeze, Cinemacraft CCE and Procoder, I've also used FCP's Compressor at home but I really need a compressor that works in windows as that is my work OS.
The problems that arise are generally a washing out of certain colours whilst being oversaturated in other areas. For example blues being dull, reds being oversaturated. Also in shots with a lot of movement what seems like a lack of resolution or pixelation. These are the problems that are visible in my best attempts both mainconcept and squeeze have produced completely unacceptable results with very obvious artifacts. Most of our work is very short so file size is not an issue so I don't really understand why I'm getting such poor results.
Here is an overview of the settings I'm using, mainly in Procoder as this has produced the best results apart from Compressor;

source file - uncompressed quicktime from adobe after effects

DVD Mpeg2
PAL
Non interlaced
High Quality
CBR
8000kbps
DC - precision 10

I've tried various filters (blur, color correction) as well but given that my preview file doesn't look as though it needs correcting I feel as though I'm applying these filters blind.

I should also state that the problems have been most prominent in our CG live action mixed work.
If anyone has any great tips or if I'm very obviously doing something wrong I'd love to know, this is starting to baffle me.

Thanks

Owen









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Charles Simonson
Re: Compression headache
on Feb 28, 2007 at 4:38:07 pm

Stick with ProCoder and make sure you are QC'ing your encodes on either a BVM or a display typical of your target audience. You do not under any circumstances ever want to trust video color reproduction to a desktop monitor, especially an LCD. Also, what format QT are you exporting from AE? I would suggest YUV 8bit as you will minimize possible conversion issues.


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Owen RR
Re: Compression headache
on Feb 28, 2007 at 5:56:18 pm

Thanks for the speedy reply, I was just choosing to use no compression the "none" option in the drop down list. Can you recommend a YUV 8 Bit codec? I have an AJA '2vuy' aka Uncompressed 8-bit 4:2:2 although no other YUV 8 bit codecs. In regard to filtering, my source material looks fine in the preview windows but as I said before it's desaturated and has artifacts when compressed. Is the application of filters a process of going back and forth between applying a filter, compressing and then correcting until one gets the desired result? If so the preview window for filters seems somewhat redundant. I don't know if this helps but we currently view our m2v's on DVD on a 32" Sony Bravia LCD screen, the input being a SCART lead from the DVD player. It is generally a similar setup to what we would assume our clients to be using, most of our work on DVD being sent to ad agencies as either showreels or previews of projects.
We used to use premiere and mainconcept, however I'm still only using a demo version of Procoder as my current task is to try and solve this ongoing compression problem by finding an encoder we can work with, I don't think that should make any difference but if anyone knows of any limitation other than the watermark it would be handy to know. Once again any help greatly appreciated and many thanks for your advice Charles.






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Charles Simonson
Re: Compression headache
on Feb 28, 2007 at 11:02:19 pm

AJA 8bit will be fine. The "None" codec is a RGB24 codec and I wouldn't recommend using it. Especially since AE has such a good color converter, even if your AE project is in RGB, letting AE convert to YUV rather than an encoder is a good choice.

Per ProCoder, personally I believe it to be the best SD MPEG-2 encoder in its price range, and I would start by just leaving all of the filtering off and encoding a 2min clip. Work from there to see if you need to apply any correction filters, but more often than not, you will not need to.

Other encoders that you may want to also try if you still aren't pleased are Episode (generally considered to have the best color conversion of any app in the sub $1K range, but I have seen some issues on MPEG-2 color in the past with Episode), and BitVice for the mac.


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Owen RR
Re: Compression headache
on Mar 1, 2007 at 12:50:40 pm

I don't get a massive difference using the YUV codec, I'm going to look into Episode and Bitvice as we may switch to compositing and editing purely on a Mac. I think the source footage is probably quite challenging, high contrast, fast motion but I wasn't expecting to encounter such difficulties. I'll keep experimenting and keep you posted if I discover anything new. Thanks again.



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Owen RR
Re: Compression headache
on Mar 1, 2007 at 1:50:26 pm

Ok I'm hoping someone will know the answer to this, and hopefully this isn't too off topic, not really to do with compression but more the display I'm using for my compressed material. I stated in the above posts what I'm viewing my m2v's on, in my frustration I tried adjusting the output signals from the DVD player which was initially set to SCART RGB, I changed it to component signal, still through the SCART cable, and the picture quality was noticeably better. I wanted to know why this is? Is the component signal not true PAL, ie square pixels? I'm a little out of my depth in this area so any help would be greatly appreciated. Thanks.



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Charles Simonson
Re: Compression headache
on Mar 1, 2007 at 3:53:12 pm

Based on what you stated above, I am led to believe that it is the DVD player causing the problem. MPEG-2 for DVD is YUV 4:2:0, and it sounds like the DVD player is doing a poor job converting the YUV color space to RGB on output. If you stick with Component over SCART, then this would be a better representation of your encodes.


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Owen RR
Re: Compression headache
on Mar 1, 2007 at 4:17:25 pm

Charles, I think you're probably right, I'm going to go and test this on some other players and see what results I get.



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Craig Seeman
Re: Compression headache
on Mar 1, 2007 at 3:24:20 pm

There's been much talk about color but I'd thought I'd mention about the other issue you noted regarding "pixels." Have you tried using compression markers in front of those "tough" areas? Creating a near by key frame might (might not) help.


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Owen RR
Re: Compression headache
on Mar 1, 2007 at 3:55:34 pm

Is that an option in Procoder? It seems as though setting keys for compression settings isn't available at least in the demo I've been using.



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Ben Waggoner
Re: Compression headache
on Mar 14, 2007 at 4:39:55 am

ProCoder will support compression markers coming in in .avi from Premiere Pro or .mov from Final Cut Pro.

Also, if you're using ProCoder, make sure you have it set to "Mastering Mode" which is one beyond highest quality. It can help with challenging content like you've got.

But the color issues are probably playback, as was suggested.


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Owen RR
Re: Compression headache
on Mar 26, 2007 at 11:24:36 am

Thanks to everyone for the advice. I seem to have partly resolved our problem to do with colour although I'm not really sure why this has happened. I have pursued a solution using my Mac at home and this is the process that seems to have sorted the problem;

TGA sequence into Quicktime Pro export using - 10 bit uncompressed 4:2:2 codec.
Uncompressed quicktime into FCP, export using Compressor using highest possible setting for DVD playback.

I've tried endless combinations with many different applications and codecs all resulting in a picture that is too dark and too high contrast. Does anyone know of a good reason why this route above should work over any other, I'd like to know whether this is a result I can replicate on PC or whether a Mac is going to be the way to go. I have noticed that the uncompressed codec I used isn't available in the PC version of QT Pro.

Thanks




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