Bad Compression Artificats on High Quality Setting!

[bo989]

Hi guys. Your suggestions in the other threads were really helpful. After colour calibrating my tuner and setting up ffdshow according to the HTPCnews guide, I had a much sharper picture (hopefully to be improved further when my new video card arrives).

Still, setting up an HTPC is a full time job, and I have a few more issues I need help with, but I'll do them one at a time. Of primary concern are the terrible compression artifacts I'm still seeing, even at the following Recording Quality:

"mmc/python2_encoding/HighestQuality-4.25GBperhr=videobitrate=9500000|width=720|height=480| audiobitrate=384"

I am using the nDVD decoder on a Ti4200 (which I don't believe has mpeg2 hardware-assisted decoding). I have temporarily disabled ffdshow (for reasons I will discuss in a future thread) and changed the renderer to VMR9 (I know my card doesn't support it, but it seemed to be the only way I could take screenshots). The artifacts were also visible before I made these two changes.

I've attached a few screenshots so you can see my problem for yourself. I understand that it doesn't look so bad in these screen captures, but its really bad in real life.

Considering the fact that I'm recording at 4.25GB/hr I don't believe it's a problem with encoding. It must be something to do with decoding, right? If so, would my upgrade to a 9600XT (which has hardware-assisted mpeg2 decoding) fix things? Any help would be really appreciated. I notice artifacts like this and they bother me to no end.

The problem areas:

Artifacts1.jpg: The lighter grey area to the right of the police dummy.

Artifacts2.jpg: To the right of the window, specifically the transition between light and shadow.

Artifacts3.jpg: The grey area in the bottom left quadrant of the picture.

Artifacts4.jpg: This one didn't show up too well, but basically the entire upper left quadrant of the picture.

Hopefully you can get a sense of the extent of the problem through these pictures. If not, then just trust me, it's quite bad in these situations. Thanks for your time guys.

*UPDATE: I just realized that the nDVD decoder icon wasn't coming up in the windows taskbar when I was watching T.V. I changed from the "Decoder" to the "Post Processor" and now the icon appears and it appears that nDVD is actually working. Could this have been the source of the problems? I'll watch a bit more T.V. and see if things have been improved. Also, is this normal behaviour for Sage? Does everyone else have Sage set to use the "Post Processor"?

**UPDATE: Ever since I changed the mpeg2 decoder filter from 'Decoder" to "Post Processor" things look great! I don't know which decoder Sage was using before, but now I see why everyone is raving about nDVD. Unfortunately, the compression artifacts are still there. For example, I was watching a country music video where they were out in the desert under a big blue sky, and you could really see obvious banding across the blue gradient of the sky. I'm starting to think it's all because of my video card. What do you guys think?

[bo989]

...bump

Are there no responses because you guys can't make out the problem in the screenshots?

I guess my primary question is: If I encode at a such a HIGH bitrate, should there be ANY artifacts, let alone artificats that are so noticeable?

[bluenote]

In theory, yes. Personally, I encountered very similar behaviour and this fuels my continual evangelization of using the 350 tv-out (as long as you don't happen to have one of the "gotcha" configs such as needing your desktop to show up on the TV, or using HDTV (something I don't know much about)).

My display on my monitor looks like crap. I played with it for several days and then got my 350 hooked up to my TV and disabled local playback and was much happier.

Hopefully someone who has solved these areas in the past will jump in and help you out.

Cory

[bo989]

Thanks for taking the time to reply Cory. So when you say you've encountered similar behaviour and that the 350 solved the problem, do you mean to imply that the artifacts are introduced in decoding? If this is the case, then maybe the new graphics card I've purchased will help things!

I don't see how the artifacts could be introduced during encoding. I use a PVR-150 and, as already mentioned, am recording at an extermely high bitrate.

Anyone else familiar with this topic? I would have thought stanger would have chimed in...

[stanger89]

FWIW, I'm not sure those are compression artifiacts.

These are compression artifacts

[bo989]

LOL. That's horrible compression. You're right, it's nowhere near that bad. But they're definitely there. You can really see them on home improvement shows when they're showing bare painted walls. The wall is blocky and splotchy whenever the lighting (and thus, the colour) isn't consistent. For what it's worth, if it were a painted wall of a consistent shade, there's no problem. That's why I never see these artifacts in cartoons, since it seems cartoons only use solid colours.

I also see it a lot in commercials where there is a radial lighting effect on a solid background (used often as a backdrop to a spokesperson or a product). The transition or gradient from the light center to the coloured background is really bad. Like concentric rings.

[bo989]

BTW, stanger: Though you don't think they're compression artifacts, can you make out the areas of concern in my screenshots?

The artifacts are not consistent across the entire picture, as they are in the screenshot you provided but they're similar. I'm looking at a blue background behind a guy on a news show right now. Everything in the foreground is perfect. But part of the blue background where there is a bit of a shadow is blocky and splotchy and clearly pixelated.

[stanger89]

I assume you resized the pictures, could you post one at full resolution?

[bo989]

Ya, I definitely can. Tomorrow, when I have some free time, I'm going to try and grab a really obvious screenshot off of some home improvement show and I'll post that at full resolution. Thanks for the interest.

[bo989]

Hi guys . Ok. I had some free time today and took more screenshots. What I did with these is highlight the problem areas and adjust the contrast to highlight the blotchiness/blockiness/banding. The reason I did the enhancement is because it is harder to notice the problem when just looking at a single frame. But, you have to believe me, it's just blatantly obvious when looking at full motion video because the size and bounadries of the bloctchiness/blockiness/banding are always changing as the camera moves.


ArtifactsHR1.jpg
------------------
Block 1: Transition between light and shadow. Both banding and blockiness are obvious here even without the enhancement.

Block 2: Bad pixelation and generally blotchy. This area was particularly bad during live TV and the blotchiness fluctuated as the camera moved almost like a lava lamp.

Block 3: Foreground with detail. No problem here. There are never artifacts in the foreground of the image or where there is detail. Artifacts only appear in large dark areas of solid colour.

ArtifactsHR2.jpg
------------------
I've only highligthed one area in this picture. Here you see obvious banding in a transition from light to shadow. Very obvious during live tv as the camera pans across the wall.

*stanger: I realize now that these don't have the same repeating pattern as the screenshot you posted. So maybe they're not compression artifacts. What else could they be?

[falchulk]

Thats just in shadows and light to dark transitions? Thats not uncommon and really, would a regular person really see that? You might try adjusting the sharpness and contrast of your TV to improve this as well.

[mlbdude]

That looks like banding to me. There are lots of discussions on the TT forums about it. It probably is a combination of your decoders/video card drivers.

[bo989]

Thanks for both of your comments.

falchulk: It is quite noticeable when actually watching T.V. I've had other people notice it without me even hinting. I could bring down my contrast I guess? But I don't know if that's the ideal solution since my contrast is already configured via the sage community guide.

mlbdude: Banding, eh? Hmmmm. Does eveyone get that to some extent or other? I'll start researching the topic, but first I need to know: what is the 'TT' forum?

[mlbdude]

Here is the thread over at TheaterTek.

http://forums.theatertek.com/showthread.php?t=6629

[bo989]

Thanks!

[bo989]

Well, DIY guy in that channel is certainly having the same problem I am "posterizing or colour banding". Thanks for the link. I'll try some of the solutions posted in that thread.

[bo989]

mlbdude, I owe you a beer.

After checking out the TT thread I made a mental list of changes I would try. Turns out the first thing I did fixed the problem. The change is like night and day. Though I can still see very slight banding in extreme transitions from bright white to a dark background, it's so subtle that I may even be imaginging it!

All I did was change the "De-Interlace Control" setting in the nvDVD Decoder properties from "Automatic" to "SMART". Now, I have NO IDEA what this control does, so if anyone wants to educae me, fell free. All I know is that it almost completely fixed the problem. Thanks everyone!

One last question for this thread: In Sage, if I set my "MPEG2 Video Decoder Filter" to "NVIDIA Decoder", the nVidia icon does not show up in the Windows taskbar and, i assume, the decoder doesn't load. If I set it to "NVIDIA Post Processor" the icon shows up and it is clear the decoder is chugging away. Is this indicative of a problem or is this how everyone is utilizing the nvDVD decoder?

Again, thanks for all your help guys. I have two other problems I'll need to tackle in the future, one dealing with audio and the other with ffdshow, but I'll save those for another day.

Happy Holidays!

[stanger89]

Glad to hear you got it working, I was just thinking from those screenshots that it looked like a decoder issue, glad mlb could put it into better words than I was going to

Originally Posted by bo989

mlbdude, I owe you a beer.

After checking out the TT thread I made a mental list of changes I would try. Turns out the first thing I did fixed the problem. The change is like night and day. Though I can still see very slight banding in extreme transitions from bright white to a dark background, it's so subtle that I may even be imaginging it!

All I did was change the "De-Interlace Control" setting in the nvDVD Decoder properties from "Automatic" to "SMART". Now, I have NO IDEA what this control does, so if anyone wants to educae me, fell free. All I know is that it almost completely fixed the problem. Thanks everyone!

In a nutshell, it switches the decoder from flag to cadence (or possibly something a little smarter) deinterlacing.

A must read (IMO) on the deinterlacing subject:
http://www.hometheaterhifi.com/volum...e-10-2000.html

[SHS]

Color banding is well know problem on PC

[stanger89]

Yeah, it was probably one of the primary reasons older nVidia (pre 5-series) cards were pretty much universally discounted for HTPCs. I know the jump from my Geforce4 MX to Radeon 9500 was a huge step much better colors. Of course now we've got lots of great cards and great decoders now.

Oh, and I think the banding in the new nVidia decoders is a bug, I seem to remember someone commenting about it on AVS now that I think about it.