MPEG2 Compressors - Banding again

[Cunhambebe]

At the beginning of the current year, I posted a couple of topics on how to render correctly MPEG2 files. At that time I was trying to re-render again VOB files (editing them with Vegas). I remember also to have written that I was having a hard time because rendering the edited files would cause a lot of banding. Somes users replied here as well as at Sony Vegas Forum, saying the problem could be field dominance and/or color space. BJ_M told me to do some dithering...it worked.
This time is not a VOB or MPEG2 file re-edited or re-rendered with Vegas. It's an original Targa sequence rendered with Lightwage (used for CGI - Computer Generated 3D Images), filters such as Video Legalize NTSC on. I don't understand why I still get some banding as I try to render the TGA sequence as MPEG2. Even Canopus ProCoder at the highest bitrate produced some banding. TMPGENC was slightly better and for my surprise, Vegas' Built-In Main Concept did the best job. I guess the problem is with all the compressors themselves bacause as I raise the bitrate to 9.800 (settings: MC MPEG2 - DVDA Video Stream), the banding is reduced, just reduced (not eliminated). Please don't say it's the resolution because I've already tried rendering with Lightwave at other resolutions. Banding is still there.
Some users may think that banding appears because I am viewing the outcome with my pc monitor...No way, on regular tv set, the banding is still there and can be noticed too (not as easily as with the pc monitor though). So. I'm here once more, kindly asking fro some more help, please!
Thanks in advance.

PS: By the way, you can go to Newtek forum
http://vbulletin.newtek.com/showthread.php?t=29895
...and try to see my pics there...They will show you more clearly what's happening. You've got to be registered to see the pics.

[junkmalle]

The process of compressing with MPEG reduces the colorspace from 24 bits to something less -- both explicitly by dropping low order bits, and implicitly by the conversion from RGB to YUV. This results in banding. You don't see it in real-world sources because there is a lot of random noise in the images and you rarely have slow, smooth transitions from one color to another across a large area. The best way to get rid of this banding is to add random dithering to your images to simulate this noise:



The left half of this image is a crop from an noisless image converted to MPEG at 8000 kbps. The right half is the same image with random noise added and converted to 8000 kbps MPEG. Banding is obvious on the left half, much less so on the right.

[BJ_M]

without seeing the pics -- i can tell you it can always be an issue .

a targa seq, is 8 bit rgb (can also be 10bit) , you are encoding to 4:2:2 , so are doing some color compression right away in YUV color space (color space conversion) ..

if you use a lcd monitor - it will look banded no matter how hard you try - a lot of digital circuit tvs also will show this. time for a good analogue monitor.

the only way to reduce this is one or more of the following:

1. increase source color to 10 or 16 bit per channel - of course you are encoding to mpeg , so that cancels out much of that benefit.

2. dither the picture by adding small amounts of noise - very effective for mpeg encoding - basically adding film grain to a non film scanned source (CGI). you do not always have to add this to every channel - i usually start with blue only , unless i add grain effect to whole picture , then i add to red and green mostly the grain effect (to match film stocks)

3. reduce the amounts of gradients used in your file seq. - not always practical ..

4. do not use any compression in your source files - even lossless compression.



i deal with this almost daily ...

[Cunhambebe]

Thanks for taking time to respond. Thanks again BJ_M to go to Sony Vegas Forum.

junkmale:
my banding looks like the one at the right side of the blue pic. It is there isn't it? So.....We cannot say that is a crystal clear quality file....Do u agree with that? If you agree with me, that means, MPEG2 files are definitely not the right choice to store movies/videos for the near future.

BJ_M:
1. increase source color to 10 or 16 bit per channel - of course you are encoding to mpeg , so that cancels out much of that benefit.
How? With one of Main Concept's options?

2. dither the picture by adding small amounts of noise - very effective for mpeg encoding - basically adding film grain to a non film scanned source (CGI). you do not always have to add this to every channel - i usually start with blue only , unless i add grain effect to whole picture , then i add to red and green mostly the grain effect (to match film stocks)
Adding small amounts of noise...remember? At the beginning of this year, I did that with some of Vegas Plug-ins (color corrector; brightnes and contrast), for the grain thing, there are other plug-ins. Since you may be familiar with Vegas..can u please specify which one should I use here?

3. reduce the amounts of gradients used in your file seq. - not always practical ..
-Wait a sec fella, I'm a newbie. lol

4. do not use any compression in your source files - even lossless compression.
-I don't. I render both souces at the same time as AVI (trying to render these AVIs as MPEG is even worse, no banding, but the picture quality is blurred, horrible) and as Lightwave Targa 32.

So I'd kindly like to ask you one more favor: to tell me which plug-ins to use and when (Lightwave phase or rendering as MPEG2 fase, with Vegas). Lightwave has some good filters such as Video Legalize and Wave (this one for image too). I'll try to upload my pics here.

[junkmalle]

my banding looks like the one at the right side of the blue pic. It is there isn't it? So.....We cannot say that is a crystal clear quality file....Do u agree with that? If you agree with me, that means, MPEG2 files are definitely not the right choice to store movies/videos for the near future.

Yes, the banding is present on the left hand side (the source image was perfectly smooth -- well, as smooth as 8 bit RGB can be). Banding is present on the right hand side too but it's mostly masked by the random noise.

Crystal clear? Well given the subject matter there's no issue of clarity (ie, spatial resolution). It's a matter of lost color depth resolution. I think what you meant is that the MPEG sample was not a (near) perfect reproduction of the original.

You are correct in stating MPEG2 is not a good choice for archiving precious recordings (in your case renderings). It is mostly a format for distribution.

[BJ_M]

10 or 16 bit per channel is done during rendering - meaning that it would have to be better than targa 32 (8 bit plus alpha), you would have to render to a 10 bit or better codec like to a cineon file or such -- the 8 bit targas are usually fine, what resolution did you render at ? we render usually at 1k - 4k and downsize if needed .. 1k is usually OK for dvd when downsized ...

you are going outside the capabilities of vegas though - vegas DOES use 4:4:4:4 internally , but outputs 8 bit no mater what ..

gradients = big chunks of solid color or fog like rendering (light and fog) ...

stick to targas -- i dont even want avi ..

[Cunhambebe]

Sorry not to have uploaded my pics the first time!

I think what you meant is that the MPEG sample was not a (near) perfect reproduction of the original.
-That's it fella.

You are correct in stating MPEG2 is not a good choice for archiving precious recordings (in your case renderings). It is mostly a format for distribution
-YESSSS!

what resolution did you render at ?
-I rendered the Targa sequence as Targa 32; there are other options such as targa 24, 32 and Targa - Don't know about if it's 8 bit and as far as I know, there's no option for codecs when rendering......(if I'm not mistaken)

stick to targas -- i dont even want avi ..
-thanks, I know that, some people told me to do so, that's the right way to render with Lightwave (targa sequence) - but it seems I still don;t know how to choose the correct file, 24, 32, targa......)

One more thing: I'd kindly like to ask you one more favor: please tell me which plug-ins you use with Vegas (if you use Vegas at all) when you do the dithering...)
Now let's see If can upload the pics here....
1.Canopus


2.TMPGENC


3.Vegas' MainConcept


hey, it worked! lol

[BJ_M]

targa 24 and 32 are the same - 32 has an alpha channel , 24 does not .. in your case it doesnt mater (no quality diff.) ..

targa can be be bottom up or top down and/or compressed (LZW compression - lossless) , there is also higher quality targas ...

targas can be in QT file also ..

i use Vegas a lot - i don't use vegas for dithering issues very often , but it can be done, i use shake and digital fusion with some nifty plug-ins .. both of those programs are not cheap ..

[junkmalle]

Targa 24 is 8 bits each of red, green, and blue. Targa 32 is the same as targa 24 with the addition of an 8 bit alpha channel.

Targa defined an optional, truely losses, runlength compression, but many programs don't know how to deal with it (I used to write software that dealt with Targa image formats). It didn't compress real world images by very much anyway.

From what I've seen from your pictures and elsewhere, MainConcept's MPEG encoder seems to add noise -- probably to reduce the banding effect you're seeing.

[Cunhambebe]

So, these are the options for RGB files when rendering a scene with Lightwave:

Deluxe RLA [.rla]
LW_Alias[.als]
LW_BMP24[.bmp]
LW_BMP32[.bmp]
Cineon FP[.cin]
LWJPEG[.jpg]
LW_PCX[.pcx]
LW_PICT24[.pct]
LW_PICT32[.pct]
LW_PNG24[.png]
LW_PNG32[.png]
LW_PShop24[.psd]
LW_PShop32[.psd]
LW_RLA24[.rla]
LW_RLA32[.rla]
Radiance [.hdr]
LW_SGI24[.rgb]
LW_SGI32[.rgb]
SGI 48 bit[.rgb]
SGI 64 bit[.rgb]
LW_SUN24[.ras]
LW_SUN32[.ras]
LW_TGA24[.tga]
LW_TGA32[.tga] - I used this one.
LW_TIFF24[.tif]
LW_TIFF32[.tif]
Tiff LogLuv[.tif]
LW_VPB[.vpb]
LW_YUV[.yuv]
Flexible format[.flx]
IFF ILBM Format[.iff]
IFF ILBM32Format[.iff]
Targa Format[.tga]

That's all. You can choose options for Codecs when you choose to save the animation as, for instance, AVI or Quicktime. No option for 8 bits around here, I guess

BJ_M wrote
-i use shake and digital fusion with some nifty plug-ins .. both of those programs are not cheap ..
great!

junkmalle wrote:
-From what I've seen from your pictures and elsewhere, MainConcept's MPEG encoder seems to add noise -- probably to reduce the banding effect you're seeing.

So? What's the big deal? Please I don't want to be misunderstood, but....how about a solution for my problem????

Thanks to all!

[BJ_M]

SGI 48 bit[.rgb]
SGI 64 bit[.rgb]
Cineon FP[.cin]

are real good - i use all of those .. of course it doesnt help you much as you have no way to encode them .. just mentioning they are great formats ... Cineon is tricky as it is log format. You need a program that can translate Log files .. (as digital fusion and shake do) ..

what do you mean no option for 8 bits ? you are using 8 bit targa now .. most of those formats are 8 bit ..

vegas looks the best above (i'm looking at it on a lcd monitor though - though a very very good one)

[BJ_M]

saying number of bit or 4:4:4 or whatever gets confusing ..

there is (partial list off the top of my head)

1:1:1
4:1:1
4:2:0
4:2:2
4:4:4
4:4:4:4
4 bit
8 bit
10 bit
10 bit log
16bit
16 bit log
24 bit
32bit
48 bit
64bit
floating
hi color
true color
16meg
32meg
64meg
32k

plus additional alpha on many of these (and some already have)


and more




the confusing part is that several of these are the same thing - just expressed different ..


most stuff people work with is 8 bit with or without alpha as junkmalle said above. That is also called 24 bit or 24 plus alpha or 32bit.

10 bit is higher quality than the 24/32 bit above ... really confused now ?

[BJ_M]

i made a test for you --

this is a single image targa file in a HD resolution .. resize as you need and try to encode it without banding ..

ramp.zip

[BJ_M]

here is a resolution chart to check your resizing (and encoding)

reschart.zip

[Cunhambebe]

Sorry, download is not working, maybe the server is down for a while...

[BJ_M]

fixed -- the server here didn't like the way i named the files ..

[Cunhambebe]

Once again, thank you very much. I'll take the test and reply as soon as possible. By the way: Where did we wind up? It seems we've found no easy solution for those bandings.

[Cunhambebe]

Here are the results of the test.
Both images rendered with Vegas MainConcept; DVDA NTSC VIDEO STREAM; 1st one, basic settings; 2nd one, VBR highest bitrate.
Other settings: Vegas timeline; Pan and Crop; mouse right click; match output aspect for each one.

1st image


2nd image


Thanks for the files, but I don't know how to use the Video Chart. Sorry.

[junkmalle]

Where did we wind up? It seems we've found no easy solution for those bandings.

BJ_M and I both gave you the solution: add noise to your renderings (some programs refer to this as "Film effect" because it simulates film grain). It's best done in your 3D program while rendering.

If you can't, or don't want to do it while rendering do it as you convert from TGA to MPEG.

If you don't like that solution use a lossless AVI codec (uncompressed, HuffYUV in pure RGB mode, PicVideo's lossless MJPEG). You won't get any/much compression but the output will be exactly the same as the input.

[Cunhambebe]

Thank you very much to take time to respond. I've already tried Vegas' Film Grain and it seems to work...I'm still trying. Thanks for letting me know that I can do that with my 3D prog too.

...If you don't like that solution use a lossless AVI codec (uncompressed, HuffYUV in pure RGB mode, PicVideo's lossless MJPEG). You won't get any/much compression but the output will be exactly the same as the input.

Sorry, but I've already tried rendering as AVI uncompressed. The result is perfect, but as soon as I render the outcome as MPEG2, the final result is definitely dark, much darker than a Targa sequence rendered as MPEG2. Don't know why. Maybe that's why most users at Newtek's forum say they always render as Targa sequences.

Thanks again. Thanks to all from VideoHelp!