Couple of questions about block noise

[antoniosgubba]

I've been making quite nice quality SVCDs for a while now..usually I use TMPGenc CBR around 2000 bitrate. The only thing that is a bit annoying is the block noise that often appears in a dark scene....I don't get any blockiness during bright fast action scenes though. When the movie, for instance, is in a scene in a dark room I can see little square blocks in the darkest parts sort of shimmering between shades of grey.
I read somewhere that this is caused by my TV not being able to distinguish as many shades of grey/black as my PC can and that a way to fix it was to reduce the luminance range with Virtualdub...I have, however, looked through all the options in virtualdub and I can't find any option to reduce luminance range....any one know how I can do this? or if there is another way to remove these blocks?

Also...and this is probably a stupid question!...does it make any difference to the quality of my SVCDs if I have my video card resolution set to 16 bit high colour instead of 32 bit true colour?...ie, will my SVCDs only get encoded in 16 bit colour if thats what the display is set to?...or does having it set to 16 bit colour only affect the display on my PC and not what I make with it.....if that makes any sense????

Gubba

[ZippyP.]

Your display setting have no affect on the encoding process.
If your source file is from the net then that is likely the cause of your blockiness. Someone else may be able to suggest some programs and filters to clean it up but I have two suggestion using TMPGEnc.

1. Under the "Quantize Matrix" tab check the box marked Soften Block Noise. The default settings are 35 and that can be adjusted depending on the source quality. I set it at 20 for a good source, 35 for medium and 50 or more depending on how bad it is.

2. Use a VBR (variable bitrate) mode when encoding. VBR uses bits more efficiently by applying a higher rate for high action scenes and a lower rate when it is not required. CQ mode is a one-pass VBR in which you pick the quality level; The final filesize is somewhat unpredictable. 2-pass VBR requires you to pick the minimum, average and maximum bitrate, the filesize is very predictable. The first pass analyzes the video and the second encodes; The encoding time can be double.

A good use of VBR will help eliminate blocks created by the encoding process. I use 2-pass overnight so time isn't a factor for me. Using your example, your settings could be: 1500 min., 2000 avg., 2500 max. and the resulting filesize will be the same as your 2000 CBR. The minimum setting for average depends on your preference, I will go as low as 1600 but like to stick to 1800 or more, adjust your minimum accordingly.

As with anything, you need decide which settings you prefer. Hope that helps point you in the right direction!

[antoniosgubba]

Thank you for your suggestions Zippy ...I shall give them a try!
I hadn't seen the soften block noise option in TMPGenc before so that does look promising.

I did have a go at using VBR once but it took forever!....although as you say if its done overnight it doesn't rwally matter if it takes 8 hours...and if it cures the block noise it would be worth it.

Gubba