Question about TBC in TRV-65 Hi8 Camcorder

[lollo]

Your answers are mostly BS as you don't provide anything to support your arguments.

Really?

You wrote "GV-USB2 drops/insert frames" and "GV-USB2" creates image distortion".
You posted no evidences.
On the other hand there are plenty of GV-USB2 capture available (including mine on my YouTube channel) showing the oppostite.

You wrote "Generally I see 2 options...".
You posted no evidences.
On the other hand I linked two real comparisons on the field, and mentioned that there are many other comparisons available.

So, who is bullshitting and doesn't provide anything to support his arguments?

Unlike you, I did all the tests with different cards and devices.

Really?

And who told you that I did not test the devices?

Also, it looks like you confuse component and composite signals.

Really?

You're the one who's confused. I did not mention composite. VHS/S-VHS is recorded (basically) as Y/C on tape. It should be captured as such. Few devices used as pass-through for stabilization feed the internal TBC with component-generated signal (I am not writing composite) and once processed generate the component (I am not writing composite) and the Y/C outputs from there. Only in this rare case is better to capture component (I am not writing composite) rather than Y/C.

Search old discussion between knowledgeable user "oln" and my self about it, here and on digitalFAQ for more details.

And that post was an answer to another user. I didn't ask your opinion about my choices, so please keep it for yourself.

Mine was not an opinion but a fact. I do not care what hardware/software you use, nor I wish to give a judgement; I am commenting to provide readers with the correct information.

[Sharc]

...However, you have to take into account how exactly this mechanism works.
To properly handle this signal you have to have a reference point. And this point is the bottom of the sync pulse.
So, every sync pulse gives a new reference point. It means that the between two sync pulses the referential voltage cannot and should not be changed by either side.

Correct.

However, because the capacitor is too small and the luma changes rapidly, the base line drifts within one field before reaching next sync pulse, which would set up the new proper reference point.

Here you seem to be mistaken. In my schematics and partlist of the ES-15 service manual this capacitor has a value of 100uF 1) rather than your 1uF.
Calculating the step response from sync tip (-300mV nominal) to reference white (700mV nominal for PAL) shows that the level shift during a scanline (means from one sync tip to the next sync tip (=64us)) is less than 0.4% for a nominal 75 Ohms load. In terms of 8 bit video this decay corresponds to approx. 1 step down, means luma 235->234 (worst case) for reference white. For the active picture scanline duration (52us) this shift is even less. I doubt very much that anyone would notice anything.
Panasonic engineers probably knew what they were doing
The issue may however be aggravated when a poor capture device has its own - too small - DC blocking capacitor at its input.

Anyway, to be on the safe side I agree to use the S-Video out of the SCART socket - if available. But be aware that some crap SCART->SVideo adaptor plugs are internally wildly wired, unscreened. Means they produce luma<->chroma crosstalk artifacts as I have shown in earlier posts. Choose your poison

Footnote 1): In 2 other service manuals of ES-10 and ES-15 this capacitor value was even 470uF(!). For this value the level shift between 2 successive sync tips becomes <0.1%, means less than a single step in 8bit luma -> irrelevant.

[CaptureCraft]

...However, you have to take into account how exactly this mechanism works.
To properly handle this signal you have to have a reference point. And this point is the bottom of the sync pulse.
So, every sync pulse gives a new reference point. It means that the between two sync pulses the referential voltage cannot and should not be changed by either side.

Correct.

However, because the capacitor is too small and the luma changes rapidly, the base line drifts within one field before reaching next sync pulse, which would set up the new proper reference point.

Here you seem to be mistaken. In my schematics and partlist of the ES-15 service manual this capacitor has a value of 100uF 1) rather than your 1uF.
Calculating the step response from sync tip (-300mV nominal) to reference white (700mV nominal for PAL) shows that the level shift during a scanline (means from one sync tip to the next sync tip (=64us)) is less than 0.4% for a nominal 75 Ohms load. In terms of 8 bit video this decay corresponds to approx. 1 step down, means luma 235->234 (worst case) for reference white. For the active picture scanline duration (52us) this shift is even less. I doubt very much that anyone would notice anything.
Panasonic engineers probably knew what they were doing
The issue may however be aggravated when a poor capture device has its own - too small - DC blocking capacitor at its input.

Anyway, to be on the safe side I agree to use the S-Video out of the SCART socket - if available. But be aware that some crap SCART->SVideo adaptor plugs are internally wildly wired, unscreened. Means they produce luma<->chroma crosstalk artifacts as I have shown in earlier posts. Choose your poison

Footnote 1): In 2 other service manuals of ES-10 and ES-15 this capacitor value was even 470uF(!)

Yes, I was wrong.
For composite signal, luma in dedicated S-video, luma in dedicated component Panasonic uses SAG compensation technique with 2 capacitors per line, trying to maintain the proper base line voltage.
For SCART output the signal goes straight from video/audio processor, no capacitors whatsoever, just a 75Ohm resistor.

That's from Panasonic Service Manual for DMR-ES15E(different submodels)

And yes, for SCART <-> SVideo dongles the wires are not shielded, but they are very short. So, I find it acceptable.

[Sharc]

Yes, I was wrong.
For composite signal, luma in dedicated S-video, luma in dedicated component Panasonic uses SAG compensation technique with 2 capacitors per line, trying to maintain the proper base line voltage.

Well, SAG correction lowers the low frequency cutoff of AC coupled signals without having to increase the value of the coupling capacitor excessivly. It still will not pass DC but eventually makes the up-down fluctuation less "nervous" by emulating a large capacitor.

For SCART output the signal goes straight from video/audio processor, no capacitors whatsoever, just a 75Ohm resistor.

Yes, usually still the best option.

And yes, for SCART <-> SVideo dongles the wires are not shielded, but they are very short. So, I find it acceptable

Yes, usually one can live with it.

Edit:
This note explains the SAG compensation principle nicely:
https://file.elecfans.com/web1/M00/0E/4B/pIYBAFocUdGAKLffACg1_gZ7dwA551.pdf