Why can't I get a good Black ?

[tatty]

I'm using TMPGEnc to code to mpeg-2. The source is VHS. Not having the first idea what I'm doing I have just accepted the defaults and coded away. I don't use any filters, or any of the various knobs and levers in the application.
The results are generally pretty impressive. The quality is pretty damn near the original and you'd have to be picky to criticise it - apart from one thing. When the frame has large areas of black the coding seems to break down. Instead of a nice solid black, I get fuzz - but not all the time, it depends on the total picture.

When the "Dark Star" drops out of light speed (how did they get 21 bombs into that tiny ship?) the ship utself is clean and sharp, while the space around it is mushy - like a poor tape. However, as the scene changes - the ship appears bigger and the % of space background drops - it suddenly switches to being perfect black - as though the encoder reached a trip level. This is quite consistent and happens in several similar scenes. The VHS tape remains clean and black.

I capture with VirtualDub at 704x576 (PAL) and code CBR to 352x288 at whatever bit rate fits the DVD. It's authored with TMPA and burned to 4xDatawrite yellows (at 2x) with Nero on a Pioneer 106.

The 'area of black fuzzing out' syndrome seems to figure in many of my coded movies now I come to look back. Of course, once you become aware of it, it becomes more and more annoying.

Is this a known 'feature' or have I just been lucky?

[adam]

You may be experiencing clipping. On the Quantize Matrix tab enable the Output YUV data as Basic YCbCr not CCIR601. Generally speaking, this would be the proper setting for a VHS source, but it also depends on your capture program and codec. But just give this a try first with a sample with alot of black and see if it solves your problem. Compare your result to a past encode. On one of them, the blacks will appear more grey. Whichever one this is, is the one you don't want. So just run this test for yourself to see how you should be setting this option in TMPGEnc.

You may just need to increase the total bitrate. What types of bitrates are you using at what resolution?

Now I haven't ever experienced this myself but many people have commented that TMPGEnc may overcompensate for the high motion scenes by taking too much bitrate away from lower motion (aka black) scenes when using VBR encoding. If you are using VBR encoding, try increasing the minimum bitrate setting.

Your problem really does sound like TMPGenc is just mismanaging the bitrate. Maybe try using the manual VBR setting and go through and find one of these scenes that causes problems. Pump up the bitrate and see if that helps, if not then the problem is with something else.

[mgh]

Large areas of darkness are tough for encoders at low bitrates. As suggested, you can increase bit rate or under custom color correction in TMPGEnc try the clip luma option.
The third party coring filter does an excellent job with virtualdub.

[tatty]

I thought I was being clever by using low res (352x288) with stacks of bits and CBR. Bit rate tends to be in the 6000 region to fill a DVD with a typical 90 minute track. Using the 'low-res PAL' setting on the TMPGEnc wizard (?) That way - so I thought - I'd get the benefit of high bit rates with the speed of CBR and still get acceptable results on a TV.

Not sure what the effect of running out of bits would be. I guess it would start to get blocky or posterized (?) but that's not quite the effect I see.

It's almost as if TMPGEnc doesn't quite know what to do with such a lump of black so creates junk. Then, the area suddenly drops to a size that it can recognise and it handles it right - if that makes any sense.

I'll have a play with those tweaks you suggested, Adam, but I'm not sure how much further I can lift the bit rate. Is it worth trying VBR? I thought that tended to rob boring sections anyway ?

[lordsmurf]

ADAM and I play this game a lot. I think he's totally off base from my tests, but he's on-par with his. Very odd.

Our results are polar opposites.

Anyway, I had a problem just few days ago, I'm still working on that project.

My fix was here:
https://www.videohelp.com/forum/viewtopic.php?t=215405

Good luck. I know how much this problem can be annoying.