improve old VHS

[mathmax]

Hi

I would like to improve an old vhs. I think that the main problem of this video is that the image is distorted.
I tried to manually correct an image so that you can see what I mean (there are horizontal lines that aren't aligned from each other) :

here is the original one:



and here is the manually corrected one:




You can see a sample of the video here: http://www.youtube.com/watch?v=iyh7KdJUWAk

I wonder if there is any software to correct this automatically for the whole video.


Thank you in advance for any advices.

[jagabo]

There's no program that will automatically fix those time base errors. What you need is an SVHS deck with a line time base corrector. Probably a full frame TBC too.

[victoriabears]

I have just completed, after 5 years effort, a full suite of many vcr's through (or not) tbc1000 or avt 8710 and feel absolutely justified in collecting so much gear, I have about 500 vhs tapes to convert and have found that one vhs plays poory on one vcr only to play near perfectly on another, if you wish to send me that vhs I will convert it for you. Also bear in mind that the material it contains (what michael jackson show is it) may be available on dvd, saving you all the trouble.

[mathmax]

Thank you very much for your answers.

Unfortunately, I don't have the VHS and I can only work on the converted files. At most, I can ask the owner to re-convert the VHS if you give me some good advices
But I know nothing about VHS transfers, and I would need you explain a little more these words:
"a SVHS deck with a line time base corrector", "a full frame TBC", "tbc1000", "avt 8710", etc.. I sounds like Chinese for me...

victoriabears, the show is not available on DVD and this VHS is the best source I know.
In case the owner cannot do an other transfer, is there any enhancements that can be done on the digital files I have? Of course I can correct a little bit the color, contrast and luminosity but is there anything else I can do?

[danno78]

Time base error can be fix only with TBC. Keep in mind that a TBC will correct the last errors made by the last recorder and the actual player vcr. If is multi-generations tape even a vcr with TBC can do much because the time base error are now part of image.
My hint: Start with the original tape and use a S-VHS vcr with TBC. This is the first and the most important step in order to get a better quality picture.

[jagabo]

Each scan line of an analog video starts with a sync pulse:

http://en.wikipedia.org/wiki/Principles_of_analogue_television#Picture_and_Synchronisation

Unfortunately, VCRs cannot spin the record/playback head at a perfectly constant speed. So the duration of each scan line is a little different. In addition, the sync pulse on the tape may not be perfectly clean making it hard for the TV/recorder to determine exactly where the line starts. The result is errors like those you are seeing -- scan lines or groups of scan lines are shifted horizontally relative to one another.

A line time base corrector adjusts the length of each scanline and cleans up the sync pulse. Here's a thread with some LTBC examples (not nearly as bad as yours though):

https://forum.videohelp.com/threads/230650-Confused-Why-a-VCR-with-TBC-if-separate-TBC-needed-anyway

Another solution is to use a DVD recorder with a built in LTBC. Like the old Panasonic ES-10 or ES-15. You can find those on ebay for $40 or so. You don't even need to record to DVD, just feed the signal from the VCR through the recorder. There are some JVC VHS/DVD recorder combos that have built in time base correctors and frame synchronizers (the latter provides a continuous video signal in case of complete signal drop out on the tape).

Someone once linked to an AviSynth software TBC algorithm:

https://forum.videohelp.com/threads/308840-old-VHS-restoration?p=1904493&viewfull=1#post1904493

I was never able to get it working outside of the demo mode.

[mathmax]

Thank you jagabo and danno78

I think it's a bit clearer in my mind now... I'll ask the owner if he used a TBC to transfer the VHS. But it maybe a multi-generations tape... if I understand well, in this case a TBC is unable to fix anything, right?

But could you confirm that without the VHS I cannot enhanced the video at all? I mean, once encoded the sync pulses are lost, aren't they? But it should be possible to have a software that analyze the image and try to finds image distortions that are caused by time base errors and corrects the alignment of these lines (just like what I've done manually...).

[victoriabears]

The owner must be ? unhappy ? with the condition of the recording?, where are you mathmax, as I love a challenge.

[mathmax]

I'm in France
I thank you very much victoriabears but I cannot send the VHS as I don't own it... And unfortunately, I'm pretty sure the owner prefer to keep it. And maybe the transfer cannot be better if the VHS is a multi-generations tape...
What would you like to do to improve the transfer?
If I owned the VHS, I'll for sure send it to you... but for now I can only work on the digital files

[victoriabears]

I am no expert in software enhancements but I think the problems with the recording need to be fixed in Hardware, so a good s-vhs vcr, JVC or Panasonic, I even have a euro Philips which just did wonders for a tape of mine, but it is a JVC clone. then a TBC onto a dvd recorder, again I would recomend a jvc , if you try software, I have only used TMPG express and it is real trial and error with the filters etc.

[mathmax]

ok, I'll give these advices to the owner Thank you.

jagabo and danno78, any idea to improve the digital files?
Certainly there is a software that can analyze the images seeking distortions caused by time base errors. Then, it should be capable to corrects the alignment of these lines. I can do it manually, so I guess a software can do it too...
Or maybe I have to ask these questions in an other forum section?

[danno78]

Certainly there is a software that can analyze the images seeking distortions caused by time base errors. Then, it should be capable to corrects the alignment of these lines.

Time base error can be fix only with TBC.

No software can do time base correction!

any idea to improve the digital files?

Manually, frame by frame. In PAL for every minute will be 1500 frame to fix. Hard work.

[2Bdecided]

We've all jumped in on this one talking about TBC errors, and how they can't be done in software (all very true) - but look at that original image carefully - do you really think this is just a typical VCR VHS TBC issue? The junk near the start might be, but in the bottom half of the frame, entire blocks of lines are shifted - rather than the usual individual line-by-line wiggles you see with typical TBC errors.

Maybe the TBC errors are so severe that they're causing this additional capture problem - or maybe there's another capture problem on top of the TBC errors.

Cheers,
David.

[jagabo]

Yes it look like a combination of time base errors and odd behavior on the part of the capture device. But I suspect a line TBC will clean the sync enough for the capture device to work properly.

[victoriabears]

Just wanted to share what I am learning as I transfer my vhs’s to dvd. Most of my vhs recordings are very good so am having little trouble using a jvc or panasonic s vhs vcr via a TBC to a jvc dvd recorder, although I am finding that even if I use a DVD RECORDER Pioneer 650H or Philips 3750(uk) or 3576 (USA) does not make a lot of difference.

I had a problem with a slightly fuzzy LP recording, and more by fluke found out that playing it on a Panasonic VCR 685 (UK)
not s-vhs connected to another vcr of the same model (Scart) onto the tbc (S Video) and dvd recorder(S Video) improved the quality to a very acceptable level, almost as good as my best.

[mathmax]

Hi

I definitely have no way to get the original VHS... But I'm writing a script to correct a part of the distortions. The script will work image by image, so I need a way to extract all the images of the video.
VirtualDub can do this job but there are some annoying thin streaks.
I have the same problem when I watch the video with VLC but not with Windows Media Player and Power DVD... The file format of the video is .VOB.
Here is a comparison:

Capture of Power DVD:


Extract of VirtualDub:


Why is there different rendering according to the video player?
Is there an other free software to easily extract a sequence of images without these streaks?

Thank you in advance for any advices.

[jagabo]

PowerDVD is doing a blend deinterlace. VirtualDub is showing you the video interlaced. Try adding the deinterlace filter in VirtualDub. If you use blend mode it will look just like PowerDVD. Yadif or ELA are better choices. Yadif:



If you're going to make a DVD leave the video interlaced and let the DVD player or TV handle it.

By the way, the DeJitter() filter in AviSynth may get rid of some of the jitter in your video:



Maybe you can fine tune the settings and get better results.

[mathmax]

Great!

Thank you very much for your explanations.

I just try to add the deinterlace mode in virtualdub and I indeed get a picture that looks like the one extracted from power DVD. But it's still a bit more blurred and the colors are less saturated... I wonder why this different rendering...



The second image you posted is just amazing... I thought there were no software to fix time base errors of a digital file. But the DeJitter() filter in AviSynth seems to do exactly what I need. I get approximatively the same result with my script. I'll try this one Thank you very much. Do you know any other software like this one to fix time base errorr?

[danno78]

I just try to add the deinterlace mode in virtualdub and I indeed get a picture that looks like the one extracted from power DVD. But it's still a bit more blurred and the colors are less saturated... I wonder why this different rendering...

Colors problems may come from color profile settings in PowerDVD (Vivid). Blurred may come from other deinterlace settings. Use Yadif with double frame rate and pick the right field first. In most cases top is first except DV file origin when is bottom.

Maybe this thread can help to better understand about software TBC:
http://forum.doom9.org/showthread.php?t=152706

[jagabo]

Deinterlace in VirtualDub:



Use any of the algorithms you prefer. Don't resize before deinterlacing.

[mathmax]

Thank you for your answers.
I've just downloaded AviSynth but it seems that there is no user interface. How can I apply the DeJitter() filter? Does this filter apply on the whole video or just on a single image?

[jagabo]

AviSynth works via simple text scripts. You can use Notepad to create the script. Save it with .AVS as the extension, not .TXT. You're script will look something like:

AviSource("filename.avi")
ConvertToYUY2(interlaced=true)
DeJitter()
Yadif(mode=0, order=0) #might as well deinterlace in AviSynth.

You will need to download the DeJitter filter and put a copy of DeJitter.dll in the AviSynth plugins folder. Same for Yadif if you choose to use it in AviSynth rather than in VirtualDub.

DeJitter happened to work fairly well with your sample image because it had black borders on both the left and right edges, and an otherwise brightly colored image. It does not work very well if the video contains dark features at the edges. It did not work as well with the first image you posted in this thread. You may be able to play with the brightness and contrast to get it working better.

[mathmax]

ok, but I guess it only works with .avi videos... and mine is a .VOB...
And how do you apply the script to a single image?

[jagabo]

The best way to open a VOB file with AviSynth is to use DgIndex to build and index (.d2v file) then use AviSynth to open it:

Mpeg2Source("filename.d2v") #instead of AviSource()

You will need to put a copy of DgDecode.dll in your AviSynth Plugins folder.

[danno78]

DGIndex can decode vob:
http://neuron2.net/dgmpgdec/dgmpgdec.html
If you have several vob file you can join in one with Vob2mpg.
Load with Dgindex the mpg file, save the d2v as mpeg_source and than import in avisynth script. You should correct the path for dll and d2v files.

LoadPlugin("D:\AviSynth 2.5\plugins\DGDecode.dll")
Load_Stdcall_plugin("D:\AviSynth 2.5\plugins\yadif.dll")
LoadPlugin("D:\AviSynth 2.5\plugins\DeJitter.dll")
MPEG2Source("k:\mpeg_source.d2v")
ConvertToYUY2(interlaced=true)
DeJitter()
Yadif(mode=0, order=0)

[jagabo]

You don't need to join your VOB files. Just open them all in DgIndex. It will create an index file for all of them.

[mathmax]

Thank you very much for these explanations.
So it works well on some images but there are huge errors on others... Some blocks are shifted to maybe... 50px !
I guess there are some parameters to define to correct these errors but I don't know how...
http://avisynth.org/vcmohan/DeJitter/DeJitter.htm

And how do you apply the script to a single image?

[jagabo]

As I said earlier, DeJitter() doesn't work well with some videos. A TBC with an analog input has access to the horizontal sync pulses:

http://zone.ni.com/devzone/cda/tut/p/id/4750#toc1

and can use them to align the lines. But once the signal is digitized those reference points are gone. DeJitter() is left only with lines of pixels. It tries to figure out where the real picture starts and ends on each scanline then adjusts their length and horizontal position. You can try tuneing some of the option in DeJitter to improve its performance:

DeJitter(jmax=16, th=50) #or whatever

You can also try adjusting the brightness and contrast of the image before DeJitter.

You can open a single image in AviSynth with ImageSource("filename.ext").

[mathmax]

I'm trying to play with the arguments of the Dejitter function() but it doesn't work better...

I'll try my algorithm. It doesn't try to correct all the errors but only the big ones. So it maybe better in final...
I'll export a sample of deinterlaced images with virtualDub and create masks with these images in Photoshop. A mask looks like this:


I just touched the brightness, contrast and colors so that the program can easily deduce the shifted blocks from the red strips.

On the other hand, I also export interlaced images from VirtualDub and the program will move the blocs of the interlaced images that correspond to what it deduced from the mask (hope my explanation is clear... ) I mean, I only need the deinterlaced images to do the masks, but at the end I work on the interlaced images to get a better video quality. Or should I deinterlace to get the best quality?

Finally, I need to piece together the images to get my enhanced video... but I guess virtualDub can do that...

[jagabo]

Along the same lines, I used some AviSynth functions to increase the contrast near the edge:

ImageSource("original.jpg")
Crop(0,0,-2,-3) #need valid size for YUV
ConvertToYUY2()
v2=Crop(0,0,20,-0).ColorYUV(off_y=-32).ColorYUV(gain_y=2000)
Overlay(last,v2)
DeJitter()

Using that on the original image in this post gave:



If you leave out the DeJitter() you'll see the very high contrast band at the left edge of the image. You will have to adjust the parameters to suit individual videos.

I would do all this while the video is interlaced. And leave it interlaced for DVD.