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View Full Version : X264 Encoding Reccomendations Revisited

KitchenStaffSupervisor
27th October 2006, 22:48
I've read plenty of guides and tried a number of different profiles (thanks Sharktooth) and custom quantization matrices (thanks *.mp4 Guy) but nothing I try seems to radically change the resulting encoded video that I'm working with. Regardless of the settings that I'm using with MeGUI, I still get some flickering in backgrounds that I don't expect to be there...and given that I've seen some amazing xvid (and divx) encodes of equal or less bitrate, I'm stumped.

Here's what I'm trying to do. Let's concentrate solely on the video for the time being. I've been trying to compress Season 2 of The Sopranos, which isn't the best transfer to DVD but it's not too bad, either (there's fairly regular dust-looking-particles appearing on frames, so it seems like it was a transfer from film.) I've worked out that to fit the whole season on one DVD, I have about 875 kbps available for video.

Given that bitrate, I tried the following (with MeGUI)

HQ-Slow/CE-High
Little / Medium Noise Filter
Full-size, and Bicubic, Bilinear, Lanczos resize filters @624x352
cqms M4G MRM, LRM, Smooth

Combinations of the above were tried - but I'm not sure if any of these agree with my bitrate assumption.

Some questions:
The default AVS script has the denoising after the resize. Shouldn't this be the other way around?

Should I be resizing the frames, or is it necessary at that bitrate? Source (before cropping) is 720x480. Definitely NOT real high-complexity encoding.

I've been using HQ-Slow because it seems the easiest choice. I change the loop deblocking to 0,0 most of the time (depending on the cqm being used if I use one), and I change the keyframe interval and min gop size to 240 and 24 (since the framerate of the source is 23.976). Is there something else I should be doing that I'm forgetting?

Thanks in advance for the assistance. I'll be happy to post short examples of the problems I'm having with the compression if someone can point me to some free hosting. I've been using a 6-minute segment from S2E01 as a test, which I can whittle down to 30-second pieces for perusal.
*.mp4 guy
27th October 2006, 23:57
The flickering could be one of two things, a problem with bframes (that can be fixed), but it more likely is a long standing problem with low motion low complexity areas and X264 (that can't be fixed). in any case denoising won't help.

Yousendit (http://www.yousendit.com/) is a pretty good short term file hosting site.
KitchenStaffSupervisor
28th October 2006, 00:02
If it's a bframes problem, what should I do to try to resolve it?

I have a feeling that you're probably right about the low motion low complexity areas. The flickering I'm seeing is often times on slow gradient walls, or in the texture on cabinets or pillows. In watching the original footage, it's apparent that these cameras are not completely fixed - might be part of the 'style' of the show.

Thx for the reply - appreciated.
*.mp4 guy
28th October 2006, 00:15
To check if it is a bframe problem set "bframe mode" to "none" instead of auto, spatial or temporal, that will fix it if its a bframe issue, however it has a small effect on compressability, so if it doesn't help you, you should make sure to set it back to "auto". If that doesn't solve the problem then you will just have to wait till a patch that fixes it is added to X264.
KitchenStaffSupervisor
28th October 2006, 00:40
Well, I tried setting it to 'none' and it had little to no impact on the result...same sorts of artifacts were present. I'll be a little less...picky.

Other than the denoising issue, is there anything else you might change about my procedure? I want to make sure I'm not missing anything.

regards...
AlexW
28th October 2006, 02:47
The flickering could be one of two things, a problem with bframes (that can be fixed), but it more likely is a long standing problem with low motion low complexity areas and X264 (that can't be fixed). in any case denoising won't help.


I've seen this flickering also (the type that isn't related to B-frames), unfortunately i don't have a clip that clearly shows this problem atm, if someone can upload such a clip somewhere then i might be able to see if i can figure out how to fix or at least reduce this flickering in x264.
KitchenStaffSupervisor
28th October 2006, 04:32
Do you need raw or compressed video?
AlexW
28th October 2006, 05:19
Do you need raw or compressed video?

I just need the original clip that shows the problem, i can generate the compressed version myself.