Avermedia Game Capture HD II - Banding problem

[DNICE_ONE]

Hi,

Just bought an Avermedia Game Capture HD II to capture 1080i 50 video but getting very noticeable and annoying colour banding in the recorded video.

The device is connected via good quality HDMI cables to the source and TV. The banding appears on HDMI pass through as well but not as bad as on the recorded video. A splitter is used to connect the capture device as well as a direct TV connection. There is no banding on the direct connection but it is visible when the video is passed through the capture device. I have also noticed that as soon as I start recording, the banding disappears from the pass through signal but it does get recorded. The device is set to record at Optimal (15Mbps) and currently I am using a USB 2.0 external HDD to record. I have tried both "Real Time Mode" and the "Standard" mode for display but the problem persists.

Has anyone else experienced this issue and is there anything I can do to eliminate this colour banding? Could it be that I have received a faulty device? The firmware it came with is 1.1.6.

I am attaching a screenshot to show the extent of the problem.

Thanks for any help in advance.

[jagabo]

15 Mb/s probably isn't enough for a hardware encoder. Try the highest bitrate the device supports and compare that.

And disable any noise reduction filters. 8 bit rec.709 and rec.601 YUV isn't sufficient to deliver smooth gradients. leaving noise in the video helps mask this.

[DNICE_ONE]

Thanks for your reply jagabo.

Just checked the manual and it says that this device can record 1080p and 720p signals at 20 Mbps but for 1080i it maxes out at 15 Mbps.

So in order to have smooth gradient It should be able to record at 20 Mbps which currently is not available at 1080i. I haven't tried recording a 1080p signal yet, will try it tomorrow and see how the recorded video comes out at 20 Mbps. Will also try and change the current source from 1080i to 720p and see if that works. Is there too much of a difference between 1080i and 720p picture quality wise?

I'll report back tomorrow. Thanks again.

[jagabo]

I don't think 20 Mb/s is going to be enough at 1080p. It might be a little better though.

[DNICE_ONE]

I don't think 20 Mb/s is going to be enough at 1080p. It might be a little better though.

You are right, tried to capture 720p at 20Mbps and still got the banding. Did some more research and found that banding is associated with the H.264 codec so its not the fault of the device.

There is no noise filter active on the device itself so no option to turn it off but read somewhere that banding can be reduced by dithering in After Effects. I haven't got access to AE at the moment but will try to download the trial version and see if it works.

Is there any USB device capturing to PC capable of higher bitrate which can avoid this banding? I don't have a super duper desktop but have a Core i3 laptop with 8GB ram with SS drive and onboard graphics. If this setup works then I can return the current device and get another one which works with my laptop.

[poisondeathray]

I don't think 20 Mb/s is going to be enough at 1080p. It might be a little better though.

You are right, tried to capture 720p at 20Mbps and still got the banding. Did some more research and found that banding is associated with the H.264 codec so its not the fault of the device.p.

It's not necessarily h.264 in general - It's that specific implementation of h.264 used by your device (and partly from 8bit limited range YUV recording)

There is no noise filter active on the device itself so no option to turn it off but read somewhere that banding can be reduced by dithering in After Effects. I haven't got access to AE at the moment but will try to download the trial version and see if it works.

There are free options to dither in avisynth and vapoursynth (you don't need AE $) . There is actually more control and options available in avisynth for dithering

[jagabo]

The banding in your sample images is a little worse average.

[DNICE_ONE]

It's not necessarily h.264 in general - It's that specific implementation of h.264 used by your device (and partly from 8bit limited range YUV recording)

Are there any standalone hardware HD encoders that you can suggest which can record at a higher bit rate? I am willing to return the capture device and buy another if it can record without banding.

There are free options to dither in avisynth and vapoursynth (you don't need AE $) . There is actually more control and options available in avisynth for dithering

Thanks for suggesting Avisynth, had a look but found it way too complicated for my abilities as it requires a script to do everything so I don't think I will be able to use it.

[DNICE_ONE]

I installed the trial version of AE and followed instructions as suggested by some AE users online (add noise) to remove banding but doesn't seem to be working for me, maybe I am not doing it right so will try again and see if it makes any difference.

Thanks for helping me out guys. Will report back if and when I am successfully able to remove this banding.

[poisondeathray]

1) Not sure what to suggest in terms of devices. But this problem is not only because of the compression. As mentioned earlier, there is an 8bit RGB/ YUV conversion going on as well - that needs to be dithered to minimize the banding. So ideally you would record in a RGB format first, eg. with a blackmagic device, recording uncompressed (huge data rates, need SSD or Raid-0 of mechanical drives for 1920x1080) - that's not feasible for most people


2) If you're trying to "fix" what you have, you need to do more than just dither. The reason is there are compression artifacts on top of it

You would need to a) denoise/deband to reduce the artifacts, b) then dither, then c) encode with dither retaining settings. "normal" or typical encoding settings won't retain the dithering. Also, the denoising stage can be fairly destructive (it can erode true details)

[jagabo]

GradFun3d(thr=2.0, thrc=0.25) in AviSynth reduces it quite a bit:


You can go stronger you will real detail. Even thr=2.0 may cause too much detail loss in other shots.