"Dot crawl" elimination help?

[Gandalf]

What Avidemux filter(s) are recommended to reduce and/or eliminate "dot crawl" from analog video recordings, and what do I do to eliminate the effect if what I refer to as "color blocking" (sometimes color differences show up in the finnished video as blocks)?

[Jan Gruuthuse]

1st: color blocking Check settings from Text menu: Edit: Preferences: [Display]:
Default Postprocessing: deselect
[ ] Horizontal deblocking
[ ] Vertical deblocking
See if this improves the issue or not. For "dot crawl", test/try other values on small selection and see if this improves "dot crawl" issue?

"dot crawl" I'm not familiar with this concept? Is that the on top line of image? Where teletext data sits? Or is it video time index? Both in black and white, 1st = small dots crawling all over that visible line? 2nd some larger stripes in left hand corner, could be right hand corner to. Long time since I've seen those.

update: see reply below from AQUAR, if this appears on border of image you could still consider one of these

You could get rid of this whilst re encoding the video:  apply Video Filter from Video Output: FiltersTransform:
- Blacken Borders Remove noisy edge by turning them to black
OR
- crop (cutting away that interference)

[AQUAR]

Dot crawl is a well know artifact in composite analog video.
It happens at highly contrasting colour edges and looks like an unstable checkerboard pattern.

It's caused by crosstalk between the luminance and chrominance signals.
Depending on the direction of the interference it is also responsible for colour bleeding.

In the analog domain, usually some kind of comb filter is used to add some constructive interference to help minimise these issues.

If you are capturing yourself, try using component signals instead of composite signals, as that should get rid of these issues .

Avisynth (run in wine!) can be used with plugin filters designed to deal with dot crawl present in digital video.
These usually need to be applied before you do any deinterlacing or inverse telecining.

Look for a filter plugin called Checkmate.dll and don't expect any miracles. 

Avidemux will accept the frames served by avisynth via its avisynth proxy (see the wiki) for further processing recoding.

Good luck.

[Gandalf]

Dot crawl is a well know artifact in composite analog video.
It happens at highly contrasting colour edges and looks like an unstable checkerboard pattern.

It's caused by crosstalk between the luminance and chrominance signals.
Depending on the direction of the interference it is also responsible for colour bleeding.

In the analog domain, usually some kind of comb filter is used to add some constructive interference to help minimise these issues.

If you are capturing yourself, try using component signals instead of composite signals, as that should get rid of these issues .

Avisynth (run in wine!) can be used with plugin filters designed to deal with dot crawl present in digital video.
These usually need to be applied before you do any deinterlacing or inverse telecining.

Look for a filter plugin called Checkmate.dll and don't expect any miracles. 

Avidemux will accept the frames served by avisynth via its avisynth proxy (see the wiki) for further processing recoding.

Good luck.

Unfortunately, that information is of no use to me because of two reasons:

1.) Component video is only intended for use with DVDs.
2.) The equipment that I'm using can only handle analog videos.

Any other suggestions?

[AQUAR]

@ Jan Gruuthuse

Dot Crawl appears at object edges anywhere in the frame and can severely destroy those edges.
If the OP just wants to use avidemux then maybe try some gaussian blending.
But I doubt anything like that will lead to satisfaction.

There are some very smart avisynth plugins for dot crawl reduction (they date back to the analog era).
I've used them on my M$ windows system, but it can work (I believe) on Linux as well.
Somthing like this (My best guess since I am not a linux user!)

Under WINE:
Install the avisynth dll and the plugins.
Create the avs script to load the video and plugin filter.
Call the avs script with avidemux proxy.

Under LINUX:
Run avidemux.
  Connect to the proxy.
  Encode and Mux.

Result, avidemux gets frame served with raw frames that are already processed for Dot Crawl reduction.
Avidemux compresses those frames as per user preference.
So anyone from the LINUX camp willing to verify this? 

@ Gandalf,

Component video is analog and its not just for DVD's!
If you are capturing from VHS tape then the next step down is to use a S-Video connection.
Next down on the list is a composite video connection.
Finally - there is the RF modulated connection (don't even try to use that).

If you are using a composite connection then that is a nice recipe for Dot Crawl and Colour Bleed.
S-video will help a great deal to reduce that Dot Crawl.

If you already have captured the video, and have dot crawl on your now digital video, you need post processing.

Avidemux itself does not have the type of processing filters that you need.
Avisynth does have various filters designed to do what you are asking.
And avisynth works hand in hand with avidemux.

Probably there are some 'point and click' standalone programs that can deal with these kinds of issues.
You need to search back in the analog era. Hopefully some forum user might recall them for you.

I have always found that the avisynth method is unbeatable for odd things like this.
Avisynth and plugins are free so why not try it.
Sorry, but I do not have any other suggestions!

[Gandalf]

Please permit me to offer my humble apology here: I just recently remembered (after taking another look at my TV tuner card) that it DOES ALLOW FOR S-video input. So to make a long story short, I did a bit of searching on TigerDirect, and found an adapter that will allow me to connect my composite video cable into the S-video input of my TV tuner card, and hopefully the results will be satisfactory.

[AQUAR]

It depends at what points the cross talk is generated.
You source device may already be pushing out a composite signal contaminated by crosstalk.
But maybe the adapter does a better job than your tuner card in separating video components.

Let us know if things are better with the adapter.

[Gandalf]

This is just an update on the situation concerning my TV tuner situation. This morning I did a quick search among the computer-related items that I had, and discovered that I already had an s-video adapter cable, so since using that, I have come to the conclusion after viewing the results, that the crosstalk in question seems to be generated from within the tuner card itself, and not necessarily from my VCR. And before I forget, I am curious as to what IS the purpose of Avidemux is, since, as you said two posts ago "Avidemux itself does not have the type of processing filters that you need."?

[AQUAR]

Avidemux is a video editor and recoding program for digital media, it also has filters for various useful refinements.
That IS what avidemux is for.

You are fiddling with analog media and analog circuitry via composite or S-Video.
Your TV tuner card has to separate the analog video signals, then process and digitise each "analog" frame (that is called capturing!).
Some capture program, associated with your TV tuner card, probably also compresses the captured video on the fly.

Dot Crawl is an analog transmission and processing problem that you embedded in the capture.
Then you want avidemux to be geared for these now rare 'Old School' problem's.
Well it is: via the support of Avisynth plus a Dot Crawl filter.

[Gandalf]

After what you said before about component video, I have decided to go ahead and upgrade my equipment so that I can make use of that technology and HOPEFULLY get my analog videotapes properly restored. I'll let you know how things turned out with it. I also think that it's only right that I offer you my humblest apologies for venting my frustration9s) out on you guys, but I had made the assumption that the computer saved EVERYTHING in digital format, because the computer is always "thinking", as it were, in digital terms. I would have saved myself a LOT of frustration had I known before about Avidemux what I know now, so thank you.

[AQUAR]

@ Gandalf

As end users we have been through that learning curve as well, so we don't give up that easily (unless we get abused!).

The video files that are created from the capture process are definitely digital.
Computer files are always in the digital domain.

VCR = Analog Video
VCR to TV TUNER = Analog Cable Connection = Component or S-Video or Composite or RF modulated.
TV TUNER = Analog to Digital conversion
Computer program = capture the Raw Digital Video
Computer program = Compressing Raw Digital Video (Make it Small)

Avidemux is one of the Computer Programs you can use for Compressing Raw Digital Video.
Virtual Dub can do the capture to Raw Digital Video.
Highly recommended you don't use a program that does both capture and complex compression at the same time.

Composite video requires "recovery processing" in the Analog domain and it creates artifacts like Dot Crawl.
S-Video requires less "recovery processing" and component only requires conversion to a different colour space (I think!).

You are capturing (digitising) what is still an analog video frame at the end of all that analog video processing.
How clean that analog product will be depends on your analog video processing equipment and type of analog connection

The Dot Crawl is created at various analog processing points (ie recovery in the TV Tuner - combining in the VCR) AND you are digitising that Dot Crawl artifact.

You have 2 choices to alleviate this problem:
1: better ANALOG processing to avoid Dot Crawl (better connections - better circuits (ie not a cheap TV Tuner!).
2: Use a smart digital filter to try and DIGITALLY process out any Dot Crawl.

Avidemux can do neither.
Avidemux plus Avisynth can do number 2.

Before you waste money on old technology equipment try number 2.
It cost nothing but a bit of effort to install Avisynth plus the Dot Crawl plugin filters.
Who knows - you might be surprised and even try other filters targetted for restoring analog captures.

[Gandalf]

When I mentioned upgrading my equipment, I should have specified that I have purchased a TV tuner card that is capable of handling component signals as youseemed to indirectly imply in a earlier post that I do:

Dot crawl is a well know artifact in composite analog video.
It happens at highly contrasting colour edges and looks like an unstable checkerboard pattern.

It's caused by crosstalk between the luminance and chrominance signals.
Depending on the direction of the interference it is also responsible for colour bleeding.

In the analog domain, usually some kind of comb filter is used to add some constructive interference to help minimise these issues.

If you are capturing yourself, try using component signals instead of composite signals, as that should get rid of these issues .

and unless I'm greatly mistaken, that is not, to the best of my knowledge, "old technology".

[AQUAR]

Analog video caters mostly to raster scan displays (picture tubes!).
Those types of displays (analog TV's, VGA Monitors etc) are now considered old technology.

Today's technology is geared to flat screen TV's/Monitors with HDMI inputs (Pure Digital!).
 
But we can agree to differ if you like.

There are different types of Analog component video (defined by their colour space - eg RGB and YPbPr) so make sure that the source matches destination.
And there is also Digital YPbPr component video (Digital Camera connection, HDMI connection).

You should get good results from capturing component video (analog or digital!).
But if Dot Crawl is already present upstream then its not going to disappear.
Hopefully your VHS recorder has component analog or S-video out.
 

[Gandalf]

One of my VHS recorders does have both., although it's a a DVD/VCR combo.

[AQUAR]

Quite possible that only the DVD part is feeding the component out.
But S-Video out for the VHS part should still be much better than composite out.