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General Question On Blotchy Videos
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Vince58
Posted: Aug 22 2002, 02:21 AM


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A General Question I have is regarding blotchy video's. What are some
of the reason's for Blotchy Video's? Is there any way to eliminate it? This is something I encounter from time to time with some of my Video Captures!

Thank You,

Vince
 
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avih
Posted: Aug 22 2002, 11:43 PM


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if i understand you correctly, you mean that u see blocks (=small squares) at the video?

if that is the case, you probably need to use higher bitrate, or use a 2-pass encoding for better results. check out the guides at http://www.everwicked.com and http://www.doom9.org
 
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Vince58
Posted: Aug 23 2002, 04:50 AM


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Thanks for your reply. What I am referring to is not small blocks. In the video it looks like some of the color is flat in the face's of people. But not
all through the video. That makes the facial color tones look blotchy or
off color some what. I hope I have explained this better.

Vince
 
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ChristianHJW
Posted: Aug 23 2002, 06:44 AM


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Vince,

can you give a bit more details on

- codec
- bitrate
- length of movie
- resolution
- resizing filter

you using ?

It seems that avih is right, even if you're not suffering from macroblocks yet the missing/faded colours indicate that the codec is truggling with too high quantizers on some frames, means you set a bitrate being too low for the resolution you chose ...

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Visit the unofficial Virtualdub support forum on http://forums.virtualdub.org - help to reduce the big number of emails Avery Lee is getting every day !!
Support matroska as container and Gstreamer as the only truely open, x-platform multimedia platform ....
 
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Vince58
Posted: Aug 25 2002, 09:12 PM


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Here is what I am using to make my Video's.

Codec: PIC Video MJPEG codec.

Bitrate: 29.97

Lenth of movie: 10 Minutes

Resolution: 352X240

Resizing filter: Virtual Dub resize internal filter

Vince
 
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SillKotscha
Posted: Aug 25 2002, 09:44 PM


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Joined: 7-July 02



I assume it's due to your codec... the PIC Video MJPEG codec is quite well known for smoothing your picture, esp. @quality set to 19 or below.

I guess this is what you realized as
QUOTE
That makes the facial color tones look blotchy or off color some what.


Depending on your input source (maybe you turned 'noise reduction' on as well) the PIC Video MJPEG will draw your picture slightly soft. Perhaps that's what you mean with blotchy ... as for example:

user posted image

ph34r.gif sorry BaronVlad, I had to steel your image to (maybe) help this dude... ph34r.gif

if it's just another story, then upload an image to be discussed here...

regards Sill

Edit: the "artefacts" around the writings are due to the compression (bmp -> jpeg)



--------------------
"Have you ever noticed that whenever Microsoft calls something 'Smart', it's definitely a feature you want to disable!"
 
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Vince58
Posted: Aug 26 2002, 02:30 AM


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Yes thats pretty close to what I am seeing. What codec do you recommend if not the PIC Video? The noise reduction filter in Virtual Dub was used also!

Thanks,

Vince
 
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SillKotscha
Posted: Aug 26 2002, 03:09 AM


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Posts: 146
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QUOTE (Vince58 @ Aug 26 2002, 04:30 AM)
What codec do you recommend if not the PIC Video?  The noise reduction filter in Virtual Dub was used also!

well, that's just an easy answer... for lossless compression you should stick to HuffYuv. But as always there're pros and cons cool.gif

My partition (D:\ = 45GB) is only capable of capturing ~ 1h20min @ 540x720. That's not enough. Just think about movies with commercials...

On the other hand you could try to raise the quality of PicVideo from 19 up to 20. That will result in even better quality (near Huffyuv) but ends up in the same space problem.

Maybe you should try Morgan Mutimedia M-JPEG v3 codec. This one gives you quite a lot of options to play around with but it is very cpu demanding.

And my last recommendation is not my favorite one but many people say it is a good alternative... XVID - but don't ask me for any settings. As for "normal" movie encoding xvid has many settings to play with... the same when using xvid for capturing.

Edit: forgot about 'noise reduction' - just disable it and let it speak for itself... maybe you're now a bit more convinced about your result(s)



--------------------
"Have you ever noticed that whenever Microsoft calls something 'Smart', it's definitely a feature you want to disable!"
 
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Vince58
Posted: Aug 27 2002, 04:27 PM


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Thanks Sill! I will let you know how I make out.

Vince
 
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BaronVlad
Posted: Aug 28 2002, 06:25 PM


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Phhh... wacko.gif To judge my video as "blotchy or off color " ! Thats not fair ohmy.gif Ok I will buy myself a better (and bigger) harddisk to get you all convinced tongue.gif

--------------------
Hochachtungsvoll

BaronVlad

user posted image

Deutsch >> Capture FAQ - Capture Guide
Englisch >> Capture FAQ - Capture Guide
 
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