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Old 9th October 2013, 07:52   #21  |  Link
Music Fan
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Quote:
Originally Posted by ChiDragon View Post
You need captures of the same frames in order to compare your options.
That's what I did (at least for 2 of the 3 recordings, the other one was maybe recorded a few seconds before but the scene is the same).

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Originally Posted by ChiDragon View Post
There is no reason to include VCR <cvbs> DVDR <cvbs> PVR-150 in the comparison though.
Why not ? I'd like to compare them.

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Originally Posted by ChiDragon View Post
To compare the Y/C separation (comb filter), the most useful test footage has low movement and high spatial frequency (sharp definition).
Ok, and when I will have recorded this kind of footage, what script should I use to compare them ?
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Old 9th October 2013, 08:38   #22  |  Link
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Quote:
Originally Posted by pandy View Post
This is not true - Y and C in each color VCR are recorded separately - "The luminance (Y) and color (C) components of the composite video signal are recorded differently. Luminance, which is in effect the black and white picture with all the high resolution components but no color, is frequency modulated on a carrier at around 3.4 MHz. The deviation is about 1 MHz and the maximum frequency recorded on a VHS tape is a little over 5 MHz (Beta is slightly different and S versions of Beta and VHS extend some of these to achieve higher bandwidths. The color signal is separated from the composite video and is amplitude modulated on a 629 kHz carrier. This is called the "color under' system."
I'm a bit clueless about analogue video, but isn't that still technically composite? It doesn't sound like two signals are being recorded on separate areas of tape.

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Old 9th October 2013, 09:25   #23  |  Link
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Interesting remark.
It seems that understanding VHS's working is not so simple actually.

Anyway, I recall my main question : how to compare CVBS and S-video captures (and also 2 CVBS captures, one with dvd as intermediary) with Avisynth, except with ColorYUV(analyze=true) whose results are not easy to understand as Y/C levels are different in all pictures ?
The subquery concerned the Philips's TBC efficiency.
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Old 9th October 2013, 21:37   #24  |  Link
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There is a MSU tool called Noise estimation metric, you could use that to compare i suppose, have a look here:
http://www.compression.ru/video/quality_measure/metric_plugins/ne_en.htm

Last edited by Mounir; 10th October 2013 at 08:31.
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Old 9th October 2013, 22:03   #25  |  Link
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Perhaps built-in Compare() func could provide some measure of difference between clips (PSNR),
or then again, perhaps not. Just an idea.

EDIT: Retasked comparison with a Merge(A.blur(1.0),B.blur(1.0)) of both comparison clips.

EDIT: Ignore, just another Brainlesss Stainlesss idea
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Old 10th October 2013, 08:34   #26  |  Link
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Thanks guys, I'm gonna have look at this.
Except ColorYUV(analyze=true), I was also told about Histogram ;
http://avisynth.org.ru/docs/english/.../histogram.htm
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Old 10th October 2013, 08:58   #27  |  Link
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Why do you want a machine to tell you which is better? Capture a scene or test pattern with appropriate content and look with your eyes.

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That's what I did (at least for 2 of the 3 recordings, the other one was maybe recorded a few seconds before but the scene is the same).
If you say so. I'm not going to spend my time cutting them to match.

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Why not ? I'd like to compare them.
Because there's no way the recombined and reseparated capture is better than the S-Video capture.
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Old 10th October 2013, 10:19   #28  |  Link
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Quote:
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Why do you want a machine to tell you which is better? Capture a scene or test pattern with appropriate content and look with your eyes.
As I already said, I don't see differences because I don't have good eyes.
Even with very good eyes, some things are hard to do without tools (hardware or software), for example calibration.

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Because there's no way the recombined and reseparated capture is better than the S-Video capture.
I'm not sure to understand what you mean, I just made tests with extracts and still have to capture the entire VHS.
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Old 10th October 2013, 11:50   #29  |  Link
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I tested Histogram(mode="levels") which shows very similar results between S-video and Composite captures.
I also tests ColorYUV(analyze=true), here are the results on a frame (S-video on left, Composite on right) ;



and another ;



And finally I tested Compare(clip1, clip2, "", "compare.log") on the exact same portion of video (15 frames), here is the log : clip1 (= clip_filtered) is Composite, clip2 (= clip_original) is S-video ;

Code:
Comparing channel(s) YUV

           Mean               Max    Max             
         Absolute     Mean    Pos.   Neg.            
 Frame     Dev.       Dev.    Dev.   Dev.  PSNR (dB) 
-----------------------------------------------------
     0    2.0545    -1.3906   51    -74     37.6727
     1    2.0336    -1.4016   35    -62     37.8019
     2    2.0766    -1.3972   55    -61     37.5089
     3    1.9896    -1.3571   43    -54     38.0099
     4    2.0342    -1.3658   36    -46     37.6620
     5    1.9665    -1.3317   40    -47     38.0741
     6    2.0110    -1.3624   42    -45     37.8413
     7    2.0702    -1.3564   42    -49     37.4747
     8    2.0049    -1.3173   50    -63     37.8216
     9    2.0380    -1.3558   32    -40     37.6822
    10    2.0190    -1.4192   40    -44     37.8700
    11    2.0492    -1.4073   36    -38     37.7398
    12    2.0689    -1.3935   39    -48     37.5861
    13    2.0683    -1.4123   53    -43     37.6493
    14    2.0834    -1.3746   37    -38     37.5346



Total frames processed: 15

                           Minimum   Average   Maximum
Mean Absolute Deviation:    1.9665    2.0379    2.0834
         Mean Deviation:   -1.4192   -1.3762   -1.3173
                   PSNR:   37.4747   37.7286   38.0741
           Overall PSNR:   37.7253
And the reverse (clip1 is S-video, clip2 is Composite) ;

Code:
Comparing channel(s) YUV

           Mean               Max    Max             
         Absolute     Mean    Pos.   Neg.            
 Frame     Dev.       Dev.    Dev.   Dev.  PSNR (dB) 
-----------------------------------------------------
     0    2.0545    +1.3906   74    -51     37.6727
     1    2.0336    +1.4016   62    -35     37.8019
     2    2.0766    +1.3972   61    -55     37.5089
     3    1.9896    +1.3571   54    -43     38.0099
     4    2.0342    +1.3658   46    -36     37.6620
     5    1.9665    +1.3317   47    -40     38.0741
     6    2.0110    +1.3624   45    -42     37.8413
     7    2.0702    +1.3564   49    -42     37.4747
     8    2.0049    +1.3173   63    -50     37.8216
     9    2.0380    +1.3558   40    -32     37.6822
    10    2.0190    +1.4192   44    -40     37.8700
    11    2.0492    +1.4073   38    -36     37.7398
    12    2.0689    +1.3935   48    -39     37.5861
    13    2.0683    +1.4123   43    -53     37.6493
    14    2.0834    +1.3746   38    -37     37.5346



Total frames processed: 15

                           Minimum   Average   Maximum
Mean Absolute Deviation:    1.9665    2.0379    2.0834
         Mean Deviation:   +1.3173   +1.3762   +1.4192
                   PSNR:   37.4747   37.7286   38.0741
           Overall PSNR:   37.7253
I don't really know how to read (interpret) these results. What do you think of this ?

Last edited by Music Fan; 10th October 2013 at 12:29.
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Old 11th October 2013, 06:44   #30  |  Link
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Quote:
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As I already said, I don't see differences because I don't have good eyes.
You said your eyes aren't perfect. So you actually have an uncorrected vision problem?

As I see it there are two possible advantages of running your video through the DVD recorder:
  • Could have a better comb filter (Y/C separation)
  • Could clean up wiggling lines

For the first it's easier to compare using a DVD test pattern. For the second you could find a scene where the camera is still and there are vertical lines, if that ever happens on the tape.

Both effects are pretty obvious to see when there is an improvement (with appropriate content), and none of the analyzing filters you ran would be particularly helpful to measure them.
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Old 11th October 2013, 07:16   #31  |  Link
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If you are looking for an opinion the pictures on the left are superior in every way to my 20/20 eyes (is that perfect?). The right looks over-saturated, look at the back of the neck on the guy on the right and the left cheek of the lady on the right. The edges are cleaner on the left, look at right elbow of the guy on the right. Left picture also has more detail look at the fingers on the left hand of the woman on the right. PSNR also agrees but that doesn't matter much. Your eyes may differ.
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Old 11th October 2013, 09:37   #32  |  Link
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Thanks for these answers !

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my 20/20 eyes (is that perfect?)
Eagles have better eyes, but for a human I guess it's near perfection
Now that you mention the saturation problem, I see it, but I have to admit I don't see very well differences on fingers and elbow. A little bit but I'm perhaps influenced by your analyze.
Anyway, the saturation problem justify I choose S-video.
And as I have to return the dvd recorder to its owner today, I don't have time anymore to make further tests.

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So you actually have an uncorrected vision problem?
It's corrected by glasses but even with them, I remarked in some situations I didn't see details as well as some others.
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Old 11th October 2013, 10:22   #33  |  Link
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I'm a bit clueless about analogue video, but isn't that still technically composite? It doesn't sound like two signals are being recorded on separate areas of tape.

David

Nope, two signal are recorded at the same time but on different frequencies (thus you can say that this is frequency multiplexing).
Chrominance is recorded in native way (as chrominance itself is AM/PM modulated) on "low" frequency, luminance is converted to FM signal and later recorded on different frequency (or rather part of spectrum) such signal is combined and feed trough write amplifier to write head (usually this is one head - combined head write/read).

This is same principle as radio - multiple radio station at the same time if each of them use different part of spectrum.

---

I've check schematics for this Sony SLV-E830 and you can easily recognize that Y and C are separate signals up to point where they are combined as CVBS and feed to video output - oscilograms clearly show this principle (there are visible colorbar signal with two part - L signal is for example on pin 25 of the IC201, where C signal is on pin 48 of the IC201.
So this VCR can be modified to provide Y/C signals.

I don't know any of the of VCR with RGB output as this require CVBC decoder (NTSC/PAL/SECAM) - there is no added value to have such decoder in VCR as required decoder already exist in TV.
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Old 11th October 2013, 14:29   #34  |  Link
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I know but for VHS things are different and s-video is not always recommended, ...
VHS is not different from eg S-VHS in how it records the signals.
However, if you detach the concepts of VHS from the S-Video ...
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.... s-video is not always recommended ...
then you might be right.

S-Video is not always recommended. The reason is that the signal has no synch, and in studios, where the cables are quite long compared to home use, any difference in length between the two cables could cause an error.
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Old 11th October 2013, 18:50   #35  |  Link
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Thanks for your explanations.

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this VCR can be modified to provide Y/C signals
Interesting. Do you believe it requires modifications (adding and/or removing electronic components) or there are just some weldings to do ?
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Old 14th October 2013, 14:24   #36  |  Link
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Thanks for your explanations.


Interesting. Do you believe it requires modifications (adding and/or removing electronic components) or there are just some weldings to do ?

Yes, for sure it require modifications, perhaps adding same video buffers but this should be not complicated - if basic principle is that C and Y are recorded as independent signal paths and later they need to be combined before output them as CVBS then outputting separately Y and C is possible and doable.

Probably some schematics for VCR is required, also datasheet for R/W video processor can be nice but even with scope some optimal source of signal can be found and used.

(im considering only to add Y/C output as this can be most important for us - to capture and process digitized video data).

I can imagine even further step as whole digital processing by capture video head baseband and DSP such digitzed signal to restore particularly precious recordings but this is out of scope for this topic definitely.
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Old 14th October 2013, 16:15   #37  |  Link
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Yes, for sure it require modifications, perhaps adding same video buffers but this should be not complicated - if basic principle is that C and Y are recorded as independent signal paths and later they need to be combined before output them as CVBS then outputting separately Y and C is possible and doable.

Probably some schematics for VCR is required, also datasheet for R/W video processor can be nice but even with scope some optimal source of signal can be found and used.
Ok, not so easy for me, and I should find the same buffer.

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I can imagine even further step as whole digital processing by capture video head baseband and DSP
I don't understand very well what you mean. What would be different compared to my current capture method ?
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