color banding - help!

[sharktacos]

In a DVD I authored I am getting strobbing and color banding in a scene that fades from black. Is there anything I can do about that?

[sharktacos]

bump

[yoda313]

Hello,

Rip the chapter that has the issue and load it into virtualdubmod. Then use video-check bad frames. It might be able to identify the issue.

Kevin

[sharktacos]

I'm not ripping from an existing dvd, I am making a dvd from original image sequences (CGI animation). The color banding is happening when I convert those image sequences to an mpeg-2 with TMPGEnc. So it is definitely happening in the encoding process. The settings I am using in TMPGEnc are:

video tab:
2-passVBR
MP@ML
10 bit
highest quality motion search
advanced tab:
progressive scan (non-interlace)
GOP structure tab:
# of I picture in GOP:1
# of P picture in GOP:5
# of B picture in GOP:2
detect scene change on

The color banding is happening in only one place where there is a fade in from black. There in the darkness of the fade instead of having smooth gradations like in the original sequence, it instead in the mpeg has strobing blocky "color banding" there or what you might call "posterization"

before:


after:


edit:
for some reason it is not displaying my uploaded images, so for sake of clarity, here is a picture on the web that is "posterized" so you can see what I mean by "color banding"
http://www.hometheaterhifi.com/qa/images/cannon-beach-sunset-posterized.gif
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[/b]

[junkmalle]

Fade in/out is about the worst thing for MPEG encoding. What bitrate are you using? Increase the bitrate for that section if you aren't maxed out already.

[sharktacos]

Fade in/out is about the worst thing for MPEG encoding. What bitrate are you using? Increase the bitrate for that section if you aren't maxed out already.

I'm using 10 bits (DC component precision) which is the highest...

[bugster]

Fade in/out is about the worst thing for MPEG encoding. What bitrate are you using? Increase the bitrate for that section if you aren't maxed out already.

I'm using 10 bits (DC component precision) which is the highest...

Thats not the bitrate. In fact you might get better results lowering it to 9.

The bitrate is the Kbps or Mbps figure.

Set it to 9500kbp/s.

[sharktacos]

ah, ok I see the bit rate. I have it set to "two-pass VBR" which allocates the bit are after checking the whole movie (in which case the bit rate is greyed out). I could change it to "constant bit rate" I suppose, I just though that variable bit rate (VBR) would be better...

[MrMoody]

No, no. Leave it VBR, click "Setting" and change it in there. Also, you will get less pulsing if you change I,P,B to 2,3,1. This will require higher bitrate (say 6000+) to work well.

Actually, the only reason to use 2-pass VBR is if you need to get to a certain file size. If you don't care about exact size, use Automatic VBR with a high Quality setting.

[sharktacos]

No, no. Leave it VBR, click "Setting" and change it in there. Also, you will get less pulsing if you change I,P,B to 2,3,1. This will require higher bitrate (say 6000+) to work well.

Actually, the only reason to use 2-pass VBR is if you need to get to a certain file size. If you don't care about exact size, use Automatic VBR with a high Quality setting.

ok, so "2 pass VBR" and in the settings:
max bitrate 9500
average bitrate 1150
min bitrate 300

if I do it "automatic VBR" then I imagine that in addition to setting it to "highest" I should also increase the max bitrate there to 9500 (it is default now to 3000).

sound right?

[MrMoody]

ok, so "2 pass VBR" and in the settings:
...
average bitrate 1150

Hokey smokes, this is why it looks like crap. This rate will give you about 7-1/2 hours of cruddy-looking video on 1 DVD-R. That's VCD rate.

if I do it "automatic VBR" then I imagine that in addition to setting it to "highest" I should also increase the max bitrate there to 9500 (it is default now to 3000).
sound right?

Yep, that will work great assuming your video is short and/or you have plenty of room.

[junkmalle]

ok, so "2 pass VBR" and in the settings:
max bitrate 9500
average bitrate 1150
min bitrate 300

Ouch! With that low an average bitrate no wonder you're having problems. I hope you're encoding at 352x240, not something bigger. Why do you want such a low average? Are you trying to put 8 hours on a DVD?

if I do it "automatic VBR" then I imagine that in addition to setting it to "highest" I should also increase the max bitrate there to 9500 (it is default now to 3000).

Highest will give you a pretty high average bitrate. Probably way too high if you really want something in the area of 1150.

[sharktacos]

Ouch! With that low an average bitrate no wonder you're having problems. I hope you're encoding at 352x240, not something bigger. Why do you want such a low average? Are you trying to put 8 hours on a DVD?

Those were the defaults. I would like to have the perfect quality full res video (720x480) with zero artifacts. What settings would you suggest for that for the min and average and max?

[guns1inger]

Max : 8400 - 9400 (I usually find 8400 is enough in most circumstances)
Min : 4200 (this can be set as low as 0, however I find it useful to force some extra bits in there)
AVG : 6000 (will give you a comfortable 90 minutes on a single layer disk. Push this up if you have more room or less footage)

These are my standard settings, and seem to work well for DV and CG footage.

[junkmalle]

Ouch! With that low an average bitrate no wonder you're having problems. I hope you're encoding at 352x240, not something bigger. Why do you want such a low average? Are you trying to put 8 hours on a DVD?

Those were the defaults. I would like to have the perfect quality full res video (720x480) with zero artifacts. What settings would you suggest for that for the min and average and max?

Well, no MPEG setting will give you "perfect" results. But you can get very good (no noticable difference under normal viewing conditions) by going with a high bitrate. How high will depend on your source material and your sensitivity to artifacts.

If you want to go only for quality subtract the audio bitrate from 10000 and use that -- roughly 9500 kbps for the video. Some players may have a little trouble at the highest bitrates -- using a constant bitrate of 8000 will probably be indestinguishable from 9500 and give you a margin of error for DVD players that have a little trouble reading writable DVD media. At these settings your talking about an hour per DVD.

If you want to go with Automatic VBR try Quality 100, Min 1000, max 9500 and see if the file size is acceptable. If you want to make it a little smaller go with a lesser quality setting. Im my experience with this mode (not much) I haven't noticed much loss of quality when dropping to the 85 to 90 range. For Automatic VBR the reason for the min and max settings are to be sure you don't get out of spec for a DVD. A very complex sequence could go over the 10000 maximum (without sound) without the limit. And I've seen some players have trouble when the bitrate gets too low (although that's been with SVCD, not DVD).

[sharktacos]

thanks for all the info!
What would value you recommend for the average bitrate?

[junkmalle]

thanks for all the info!
What would value you recommend for the average bitrate?

For Automatic VBR there is no average bitrate. The file will come out to whatever size is needed to deliver the desired quality.

For 2 pass VBR you pick the average based on the size of the file you want. Like gunsl1nger said, 6000 will get you about 90 minutes on a DVD and in most cases gives good image quality. 8000 will get you about 60 minutes on a DVD at about the highest quality you can get with DVD. 4000 will get you about two hours but you will probably start to see degredation of the video.

For the single pass methods you can just run a short test of your fade-in and other representative parts of the source. That will give you a feel for what to expect for the rest.

For the two pass VBR method you really need to run both full passes because the codec portions out the birate based on the desired size and how much is needed for different parts of the video. Parts that require a high bitrate will have take bits away from parts that require less bitrate. So the codec has to examine the whole file in the first pass, then encode the whole file in the second pass.

[sharktacos]

Thanks so much for everyone for all the great help!

One last question:
I read that certian DVD players have a hard time with dvd-r disks that are made with higher bitrates. Does that refer to the bitrates that we are talking about here?

My main concern is not really file size (the animation is only 8 minuites so I'm sure it will fit) but quality and compatability. So I was concerned with the high bitrates not being compatable with some players. I also would appreciate any other tips you may have about compatabilty issues with encoding.

thanks!

[guns1inger]

Theoretically, to carry the DVD logo they must be able to handle the maximum permissible bitrate. This is certainly true for pressed disks, although DVD-R doesn't really fit in the base spec.

To be honest, even with CG I haven't foudn the need to push the bitrate right to the top. Consumer DV is quite happy with an average of around 6000. With a 2-pass VBR encode with a high (say 9400) bitrate, you should get good results without straining your player.