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Old 3rd April 2005, 20:53   #1  |  Link
Morpheus_xx
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How to remove diagonal bars in video?

Hi,

I capture series from analog TV using a Hauppauge PVR150 (720x576, VBR max 12MBit).

Only on one channel (German RTL2) I have strange diagonal "bars" on captured video. They become stronger and then weaker and so on, like "flashing".

Screenshot:
http://mf-the-one.netfirms.com/sg1_bars.htm

Does anybody know if there's a good way to remove this???

Or better, what cause this noise and how to avoid it?

Thnx,
Morpheus

ps: where is my attachment

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Last edited by Morpheus_xx; 3rd April 2005 at 21:00.
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Old 3rd April 2005, 23:33   #2  |  Link
Morpheus_xx
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While searching the forum I found the "defreq" plugin.

Now I try to use it. But I can't find good parameters. The sample on the website (http://www.avisynth.org/fizick/defreq/defreq.html) is quite unlike my frequency spectrum. I do not have clear hot spots

And it's alternating frame by frame (see frame 9750 vs. 9751, middle region).

Images and avisynth script see link in 1st post.


Maybe someone can help?

Last edited by Morpheus_xx; 3rd April 2005 at 23:36.
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Old 4th April 2005, 22:10   #3  |  Link
Fizick
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Morpheus_xx,
Your picture is too dark,
And i do not see any diagonal lines on it.
Sorry.
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Old 4th April 2005, 22:17   #4  |  Link
Fizick
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Morpheus_xx,
Your picture is too dark,
And i do not see any diagonal lines on it.
Sorry.
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Old 4th April 2005, 22:36   #5  |  Link
Morpheus_xx
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well, you're right. was a bad sample ;-) (my display is also quite bright)

this one should show it better.

please also see link above, there's the debug-output from defreq.
any hints for parameters?

thanks in advance
morpheus
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Last edited by Morpheus_xx; 4th April 2005 at 22:39.
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Old 5th April 2005, 06:17   #6  |  Link
Fizick
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try fx=12, fy=-5
I see small bright sharp dot on spectrum there.
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Old 5th April 2005, 19:53   #7  |  Link
Morpheus_xx
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thank you for reply.

I tried your settings, but unfortunately the difference of the filtered clip was not visible.

So I made some other tests like:
DeFreq(fx=11,fy=98,sharp=90,fx2=96,fy2=100,fx3=61,fy3=98,fx4=64,fy4=-97)

This seems to help a bit. I had to use such high values to focus some spots.
Is this the right way? Or am I completly wrong?

Can I adjust the "strength" of DeFreq ? I would need the effect "stronger".
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Old 11th April 2005, 11:45   #8  |  Link
vcmohan
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I have just authored a plugin FanFilter (The name is due to my assosiation with Seismic data processing for Oil and Gas). I have tested this on your two images and find that with default settings the noise is gone. I see some horizontal streaks which probably are on the original.Some smoothening and bit of edge is seen . Smoothening gave a pleasing effect.
The plugin should be shortly available on www.avisynth.org/warpenterprises page for a free down load.
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Old 11th April 2005, 17:07   #9  |  Link
Morpheus_xx
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Sounds good! I always like to test new filters :-)

It's not on the page yet.

Can you post the filter here?
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Old 12th April 2005, 10:47   #10  |  Link
vcmohan
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warpenterprises take a few days to post the link on their page. Meanwhile following are the urls for images output by Fanfilter

and


I do not know whether this is the way to do it or delete url tags!
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Old 12th April 2005, 13:40   #11  |  Link
Morpheus_xx
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wow, amazing! I can't await to test it on the clip!

Can you tell me about the performance? Most of the existing denoise-filters are imho quite slow.
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Old 12th April 2005, 15:38   #12  |  Link
WarpEnterprises
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meanwhile by proxy of vcmohan:

http://www.avisynth.org/warpenterprises#fanfilter
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Old 12th April 2005, 17:17   #13  |  Link
Morpheus_xx
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I've made a first test with default values.

As I said before: amazing! For this problem it's the best filter I've tested yet!

And performance is also very good.

I'll do some more tests with the parameters to see the influence to the video.

Thank you, great work!
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Old 12th April 2005, 18:14   #14  |  Link
Wilbert
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@vcmohan,

Is there a reason you make those great filters without releasing the source?
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Old 12th April 2005, 19:36   #15  |  Link
trevlac
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Yeah VC,

I'd love to know more details.

I've been fooling with this frequency stuff in my spare time. I loved your post because it gave me some clues.

Threshold the black for example.

Anyway ... so by default does 16 mean we start at 32/width and remove periodic frequencies? What's the period? Do you remove or reduce them? Is the 5% threshold based upon DC as the max?

Here is my try at this..... No thresholding the black. And i did not smooth after the filter. I was really just guessing.




edit:
Image is only processing lines 100-476 Previous image is as
http://trevlac.us/pics/sg1_61190X.jpg

Last edited by trevlac; 13th April 2005 at 18:53.
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Old 13th April 2005, 06:19   #16  |  Link
vcmohan
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I am happy that you found the filter does a good job.
As for why I do not release the source:
1. I am a novice at C++ programming and am afraid they will be too many poor programming pieces.
2. I find that for many plugins hosted on the warpenterprises page source is not available.
3. If I get feedback I would love to work on my code continuously. I have retired from work in 1992 and can afford to devote time.
4. Of course may be in not too distant future the sources will be made available.

Regarding Parameters:
Lambda is related to wavelength of noise freq. It may be half or some other ratio. The plugin examines data over this moving window.

Threshold is to limit corrections in dark areas. Amp limits in brighter areas.

I examined the actual pixelvalues of the image using pixelvalues plugin and found that normal freq domain methods may not work as the actual level of interference is very low. In very bright areas it is not even seen.

To avoid artifacts one need to ensure that these three parameters have the least values that can remove noise.

The algorithm used is very simple, and so is quite fast. The seemingly diagonal nature is because the scanning is done in a particular order and with some padding values in TV signal. It ( the angle of diagonal) has no effect on working.

I have just introduced RGB32 and RGB24 color formats also.Earlier I had some misgivings about working in these formats. But I find my algorithm works in these formats also. The defaults however left out some noise. It appears it requires higher threshold and amp parameters. This updated version I will release by end of month.
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Last edited by vcmohan; 13th April 2005 at 06:25.
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Old 13th April 2005, 06:51   #17  |  Link
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Quote:
Originally posted by trevlac
I'd love to know more details.
I gave some details in my post above.
I use threshold to categorise whether it is noise or signal. If deviation is more than threshold signal.
Eventhough the interference would be same over the image, it occurred to me that our eyes may be playing tricks and so notice it more in darker areas. Thats the reason to introduce amp factor.

Quote:
Anyway ... so by default does 16 mean we start at 32/width and remove periodic frequencies? What's the period? Do you remove or reduce them? Is the 5% threshold based upon DC as the max?
Lambda default is 16. Lambda has a relation with wavelength (along width axis) of the periodic noise. I use it as a span over which find deviations and using threshold and amp factors correct. Thats the reason some smoothening may be seen in the result. I do not per se use any other smoothening.

Quote:
[B]Here is my try at this..... No thresholding the black. And i did not smooth after the filter. I was really just guessing.[B]
Its not clear to me whether you are using my plugin or your own. I find that the white streaks in the black areas, a spot in one eye and still slightly visible diagonal noise are somewhat unsatisfactory. There appears to be much less smoothening than in my example. If you are using my plugin then there must be a bug which is producing those white streaks.
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Old 13th April 2005, 14:43   #18  |  Link
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@VC

Thank you for the details. I completely misunderstood what you were doing. I thought you were working within the frequency domain.


Quote:
Originally posted by vcmohan
Its not clear to me whether you are using my plugin or your own. I find that the white streaks in the black areas, a spot in one eye and still slightly visible diagonal noise are somewhat unsatisfactory. There appears to be much less smoothening than in my example. If you are using my plugin then there must be a bug which is producing those white streaks.
I was using a virtualDub filter I created to learn about the frequency domain. And yes ... the white streaks are a problem, but you showed me that they can be thresholded away. I updated my picture. And I too see some noise left. As you pointed out ... this might be a limit of the frequency domain. I thought you filtered and then smoothed to remove this.

PS: I am not trying to better your work. I am just trying to learn about an area of interest. Your filter clearly does a great job and is ready for general use. My filter is not in a usable form to do this processing. It's main purpose it to show me the fourier image. To process a video would be terribly slow.
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Old 13th April 2005, 15:55   #19  |  Link
Wilbert
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Of course you are free to not release your source. If you do people might learn something from it. Anyway, some comments.
Quote:
As for why I do not release the source:
2. I find that for many plugins hosted on the warpenterprises page source is not available.
3. If I get feedback I would love to work on my code continuously. I have retired from work in 1992 and can afford to devote time.
4. Of course may be in not too distant future the sources will be made available.
2. Most of them have the source included (the ones who haven't can be counted on two hands; or one hand if you exclude your plugins ).
3. What does that have to do with releasing sources? In general, people will ask the author first if they want to see something changed/added.
4. That would be very nice
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Old 13th April 2005, 16:35   #20  |  Link
Malcolm
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interesting filter!
but if you compare the 2 pictures of the woman (unfiltered and filtered) by switching back- and forth, you can see that in all corners of the picture some slight diagonal bars are introduced. (exactly like the ones that are removed in the middle of the picture).
looks like an 'overcompensation' effect.

Greetings,
Malcolm
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