Compressor-Resize and pre-encode results in weird Color switching during playback

Hi everyone,

I've returned to the smartet forum I know of. Currently I am working on a project. The end goal is to have a video file Approx 1.2 gigs (give or take). The video will be made available for download as a purchase. The videos is currently available for purchase on a DVD which is mailed to the client.

I am currently working on cropping the original footage (Captured 8 bit uncompressed from Tape) and doing some pre-compressing work on it (black/white restore, Gamma correction, contrast sharpen etc...) I'm exporting this "prepped" clip as "None" under compression type. I will then encode that file to a H.264 mp4 file at full size.

What I am running into is, upon cropping and prepping my file, when I view the resulting video, the colo or chroma, or temp of the picture (whatever you want to call) randomly switches back and forth from being kind of a warm reddish temp, to a yellow cold temp. About every 3-4 seconds.

Has anyone run into this? Any suggestions? I have tried turning a plug in off one at a time and re-submitting, but I can't seem to narrow it down. I may have missed something too.

Thanks in advance for your help. SOrry this was so long and detailed.

Would the codec be at faulty? Should I be using a JPEG export on this original file?

"None" (thanks, Apple, for choosing such a dumb compressor name) is not suitable for video. It's an 8-bit-only RGB format. It's extremely difficult to preserve dynamic range across a YUV-RGB conversion, especially when you're limited to eight bits.

I'm confused about your workflow. Why would you use Compressor filters (I assume that's what you mean by "black/white restore" and the rest) this way? What's your overall workflow pipeline here? It sounds like you're doing things in a highly unconventional way, but maybe I'm just misunderstanding.

I may have overcomplicated my explaining. Basically the idea behind what I'm doing is to first do all of my resizing, cropping and "tweaking" to the video, then encode it to an H.264 encoded mp4 file. So it's a 2 step process. By doing my color adjustments as well as all the other filtering, first I'm hoping to feed the encoder a better video. One that is easier to encode.

Do you have a suggestion of a better workflow? It sounds like you avoid sing Compressor's built in filters. What would you use?

Well ? yeah. I mean, for things like correcting dynamic range or overall primary color correction, I'll either use Colorista in my FCP timeline, or for stuff that's too finicky for Colorista, I'll pop the shot over to Color. I wouldn't rely on a Compressor filter to do primary color correction.

For repos or pan-and-scans, I'd just do that in Final Cut directly as well. FCP doesn't scale shots especially well, but it's fine for, say, doing a 4x3 extraction of a 16x9 frame.

What precisely do you need to do to this material?

I'm not as much doing color correction as I am prep work for encoding. I'm also not working ot of FInalcut except to capture my video. I'm strictly talk about encoding material here. So to put it into "Color" would be way too much detail and control for what I'm doing. I'm basically wanting to get the video to the point that the encoder will do a better job of it. My current workflow is pretty common amongst encoders. In fact Ken Stone writes an in depth article on the importance of pre-processing on his site.

Back to my main question, I'm really asking for help here regarding the anomaly I described above. Have you run into anything like that before? Or anyone else?

The video I get has already been edited, comped, overlayed with graphics, and color corrected. It's broadcast ready. I mentioned above that this is usually distributed on a DVD for Sale. I am working on a version that would allow the customer to download the file instead of wait for a DVD to be mailed to them.

They key here is that what I'm doing is not video color correction. It's pre-processing for encoding. A completely different workflow than what an editor might do. My job happens way later in the process.

Okay, then you might have better luck in a forum that's frequented by people who do Web stuff. Though there are notable exceptions, most people here work in broadcast exclusively.

But going back a few steps, you're definitely making a mistake by doing a YUV-to-RGB-to-YUV conversion.

Well, I guess that's one way to help. Don't want to make this a personal disagreement, but there's a huge community on this forum that take broadcast material and make it available via web. No offense to you but I think I'll hold out for someone else to respond to this post as I always get awesome help here and try to contribute as well.

Hope I haven't offended you, but I think we're coming from two different worlds. Maybe they shouldn't be viewed as such different worlds as the line between broadcast and web is blurring more and more each day.

Jeff is right on the YUV-RGB-YUV conversion, although it shouldn't cause any kind of chroma flickering, not randomly.


>I'm exporting this "prepped" clip as "None" under compression type. I will then encode that file to
>a H.264 mp4 file at full size.

You need to provide a LOT more detail about your workflow. Are you exporting from FCP via QT conversion?

What is your source tape? D-Beta, captured via SDI? Is the footage broadcast legal? Does it clip on the RGB parade? What is your render setting in FCP (hit apple 0 for sequence settings to check that)? You should be working in an Uncompressed 8 bit timeline, and export a QT movie and encode that.



www.strypesinpost.com

Thanks for the questions. I'll do my best to answer them.

I receive an mpeg IMX tape that I capture in FCP at 8bit uncompressed via a Kona 3 card. The footage is from a DVD product which we produce and sell. So it's definitely legal. It is also been through post production and ready for distribution.

I then export that video from FCP as a Quicktime (uncompressed 8 bit) file to then process in Compressor. There is no rendering done in FCP as I capture and time line settings are identical.

What I did just find out, was that the chroma switching I was experiencing seems to be coming from the Noise Reduction Filter in Compressor. I have it set to

Apply To: Chroma Channels
Iteration: 2
Algorithm: Average.

As soon as I turned off the Color Correction filter this color switching seems to have stopped. Does this ring a bell?

Thanks a ton for your help!

We def need more info on your source...tape from what? HD? SD? Interlaced? Is it coming from an analog source?

QT filters can be useful for batch processing, etc, but can be finicky. For reliability, i would use FCP for your color correction. Also, use ProRes HQ or the original 8-bit uncompressed, the flip that to H.264. "None" may sound right but it will only give you trouble.

The article on Ken Stone is good but i would avoid the noise reduction, which only makes things soft which the h.264 conversion will do anyway. In fact, i often over sharpen slightly to make things remain sharp in a low-bit rate h.264 stream. Gamma is def important because as h.264 throws out information, it often washes out the image as it softens it. If it's SD, def crop the action safe area out as you were never intended to see that anyway, and will give more focus to the important area of the screen.

Anyway, my two cents...and yes there is a large number of us who dont work exclusively in broadcast. In fact, all my broadcast work gets put online the same day it airs so it's almost one in the same. Let alone the DVD delivery side of things...this is forum for anyone who deals with Final Cut, regardless of what they do with it.

Yea, it's not about broadcast vs web. Grafixjoe has stuff that goes out to web as well as broadcast... I haven't exactly gone to web, but i'm keen on learning more about it.

Actually, there's slightly more to the Gamma setting. PCs and Macs have default to different gamma settings.

[www.kenstone.net]

>Also, use ProRes HQ or the original 8-bit uncompressed

The same concept applies. Export native, you bypass double compression.



www.strypesinpost.com

Ok so I take it back. I thought it was the Noise Reduction Filter, but now it's still doing it. It seems to be the Color (mid tones) filter that is doing it. So no one else has run into this? I'm using the ProRes codec now for my pre-encoding work. Looks much better. Thanks.

OK i do a lot of web stuff.

is the shift in the lightness of the colors or the detail?

Does it look at all like a gamma shift?

is it getting muddier in certain areas of motion or is there an over all muddiness?

""" What you do with what you have, is more important than what you could do, with what you don't have."

> > > Knowledge + Action = Wisdom - J. Corbett 1992 """"

Thanks for your response!

I haven't noticed a muddiness. It's more than a gamma switch too as the color tone or temperature of the picture flips from a warm color to a cold yellowy tone. Someone mentioned it could be that it is flip flopping in the deinterlace process from top to bottom etc.... That almost makes sense, except I'm not sure what I would do to combat that.

Can you shed any light on that thought process? Or do you think that's not very probable?

when you are on the quality tab and you are looking at the custom frame controls. Are they all set to best?

Have you attempted to do h264 from quicktime itself?

can you show me a clip ran thru with out your receipt and one with the correction?

I see the same shift but it doesn't often happen in the chroma other that a loss of some blacks which jumps the chroma over all.
Normally, I just +7 to 10 contrast / -2 to 5 brightness / +3 saturations / -2 tint if needed

at times i +1 the anti-alias depending in the style and action.

""" What you do with what you have, is more important than what you could do, with what you don't have."

> > > Knowledge + Action = Wisdom - J. Corbett 1992 """"

Ok so here's a link to the video showing the color switch.
video: [jmmdownloads.att-idns.net]

It happens right at: 00:00:25:18


Here's a snapshot of my frame controls settings I used on it


Here's a screenshot of the Brightness/Contrast Settings I used.


Does that help at all? I'm not sure I completely understood your question(s), so I tried to post my settings in hopes that it will help answer them.

Thanks again for your help!!!

You may not be able to correct that. what i looked at was the 1 second before it cuts to the speaker.

The hue change seems to be in the smoke of the lights and any thing in it. This comes most likely from the camera's temp or luma shift.
The rest of the file seems fine.

when you encode of coarse you there is loss. and in some cases this loss causes shifts in the chroma which cause otherwise un-seen changes in video to be more apparent. Like temp shifts when a camera is on auto.

I can see why it is annoying as the shot moves so smoothly and then that sudden jump. However to fix it you need to either tell the editor or blade the shot in some edit program and apply a color correction to it. If you choose the edit program then you may risk slightly, tepidly, more overall compression but will smooth this problem.

""" What you do with what you have, is more important than what you could do, with what you don't have."

> > > Knowledge + Action = Wisdom - J. Corbett 1992 """"

Interesting. What I can't figure out is if I encode it in something other than Compressor, MpegStreamclip or even something like HandBrake it doesn't show up. It's only in Compressor.

frame controls > conversion rate > best

see if that helps i have seen some differences with that.

""" What you do with what you have, is more important than what you could do, with what you don't have."

> > > Knowledge + Action = Wisdom - J. Corbett 1992 """"

I'm going to try that for sure. I always thought that was only needed if you were changing the frame rate. Am I mistaken?

RANT>>
you know honestly i don't think that compressor3 is as good as compressor2 for conversions.

i have a lot of old receipts that would give me spectacular results in comp2 but in comp3 the same receipt gives me mud.

I normally use QT to make the H264 just for this reason.

DV Kitchen is a great tool for what you do. It also allows you to choose quicktime export options and it auto uploads to the server. You can even overwrite a file on the server.
I have only had it for 2 weeks but its very nice.

""" What you do with what you have, is more important than what you could do, with what you don't have."

> > > Knowledge + Action = Wisdom - J. Corbett 1992 """"