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  #1  
02-17-2022, 05:24 AM
Cortez Cortez is offline
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Greetings,

In a very recent post (and in olders as well) LordSmurf often uses the following term:

Decent explanation of line TBC, but not for frame TBC. Frame TBCs aren't just for "very bad tapes", but all tapes. Line cleans the image, frame cleans the signal. You need both.

What is the meaning behind that?

I falsely thought that VCRs send out the signal (= image + sound) throught the cable what we can see and hear on television. It is more complicated because there are different cables for video and left - right audio as well. Even the S-Video cable has at least 4 different pins for ?channels?.

I thought that what we see on TV and what we hear is the signal that came from the VCR and processed by the TV so when we clean the signal we also clean the image and sound quaility but this is totally false because image + audio is not equal to signal, right?

The only way i could do for better understanding is to experiment a little:

I put an official pre-recorded VHS cassette in the VCR directly connected to the PC. When i hit the play button the movie is enjoyable: good image and audio. When i hit the capture button in MMC, the captured video has the artificical error by Macrovision: almost full green screen by every "second" picture.

Then i send the signal through the TBC-1000 and movie is still enjoyable but the captured footage is also good because TBC-1000 cleaned the signal (eliminated the artificial error).

So after that i am confused because the same "signal" has different output directly streamed to the display (OK), and captured to a single file (HAS ERROR).

My brother asked a funny question that how can the VCR know that it is connected to a display or a capturing device? So it sends the error only when it connected to a capturing device.

I think the artificial error is always there hidden in the signal or sent on another channel as a wrong checksum or something?

Can somebody explain a little bit deeper the technical details about it to resolve my confusion?

Actually this was the first time i turned on the TBC-1000 i bought from LS and i am very satisfied with the result right at the first attempt.
Thank you very much.

I need more capturing to compare the footages side by side (with and without TBC) even with bad tapes.

Thank you for the information.

All the best!
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  #2  
02-17-2022, 06:43 AM
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lordsmurf lordsmurf is offline
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Another way to look at it is this:
- line TBC is intraframe / in-frame / in-picture only
- frame TBC is interframe / frame-to-frame / temporal

Different axis.

Video is a signal, maths, not an image. It's not film. The image is constructed (modulated) from the magnetic recorded data (ignoring broadcast for now). It's also 3D, not 2D. X, Y, and Z temporal.

And yet another way to look at it:
The different TBC attack different axis. Line is X Y and frame is Z. XY is the image data, and Z is non-image data. Both data are required.

Macrovision is an anti-copy. Anti-copy is an artificial video errors. Both natural and artificial errors can signal errors. Non-visual problem data. Frame TBC removes it. Line TBC does not.

You can condition XY without Z, and Z without XY. But you run into capture problems. You want to clean XY+Z, both visual and non-visual. Intraframe and interframe. So both line and frame BC are required, not optional. At least if you value quality, time, and your sanity.

The question isn't funny, but understandable. Most capture cards are programmed to know an artificial errors when seen, and halt, or for AGC to go nuts. But here's the problem: again, natural errors can appear as the fake ones. So a homemade tape can halt, have AGC issues, or whatever bad things happen to the capture.

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  #3  
02-17-2022, 07:27 AM
Cortez Cortez is offline
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Thank you for the answer LS,

for me it is still too complicated. Some example would be more understandable.

Please correct me if i wrong but this is what i understood (maybe falsely).

XY defines the picture, the image and Z is the what happens between the pictures? So a color data belongs to more like XY and FPS to Z?

So what we see on the screen is XY (pictures after pictures), but Z says how fast should the screen repleace these pictures? Thats why if you don't have Z correction your audio and picture goes desynchronisation? Like the audio is delayed or late?

So the Macrovision's artificial error is more like temporal errors because the frame TBC can correct them?

Line and frame TBC can correct natural and fake (Macrovision) errors no matter which one occurs (maybe both)? Those doesn't care which one, it must be corrected.

Different capture cards or i would say devices can act differently for the same error? Some go nuts and make the quality even worse, some just crash, some doesn't crash but can do nothing to correct the error and the best can handle the error to improve quality?

What about the TBC-ish devices? Like the budget ES-10, or the Canopus AVDC-300 TBC (but actually line TBC) devices. If a corrector device doesn't provide frame TBC it cannot eliminate Macrovision? I don't wanna capture copyrighted materials but this is a very good, illustrative example in this area where Canopus is the allmighty capturing device and i need to bring some reason why it is not the best.

I will do a lot of capturing for compare the result with and without TBC-1000. I think the difference will be more significant for bad tapes.
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  #4  
02-17-2022, 08:23 AM
Hushpower Hushpower is offline
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This is what a line TBC does/fixes (in this case, an ES-15 [ES-10 similar], which we all know isn't actually a line TBC per- se ):

Note the wavy edges and jumpy frames which are corrected by the ES-15 (I don't know how effective it is against Macrovision):

http://www.digitalfaq.com/forum/vide...html#post82879
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  #5  
02-17-2022, 09:17 AM
dpalomaki dpalomaki is offline
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Lets forget audio for a moment. It is separate from video.

Maybe think of it as follows:
XY is a single image, a field/frame. In film this would be a single cell.
Z represents a stack of images separate in time by the frame/field rate.
Thus the TV image is a stack of XY images displayed sequentially (the z direction).
(Different from film in that film presents XY the image all at once, while TV paints it one scan line at a time.)

But the TV image represents only a portion of the video signal.
Thinking NTSC analog video, a frame is composed of 486 scan lines and 39 line equivalents with timing and other non-image data. (Digital typically only uses 480 lines because the other 6 lines are overscan on traditional TV sets and not seen).
An individual scan line is about 63.5 microseconds long, of which abut 52.8 microseconds is used for image, the remaining 10.7 microseconds is used for timing and synchronization. Digital typically samples its 720 horizontal pixels from the 52.8 microseconds of signal.

Macrovision places an added signal in the non visible image areas that most TV sets will ignore, but it fools VHS VCR electronics into messing up the recorded image. Manufacturers added special circuitry to capture cards, recorders, and Video8/Hi8 VCRs to detect the Macrovison signal and inhibit capture/recording. In the USA, and probably most other countries, this anti-copy feature has been required by law for the past 22+ years. Before that it was likely an unintended feature of VHS.

Composite (typically yellow RCA connector) and s-video cable only carry video information - no audio. The s-video carries the video as two signals, black and white image, and color decoding information, while the composite cable has the two combined and somewhat overlapping on the same wire. S-video is generally better than composite because a signal separation step and resulting artifacts are eliminated. (The RF connection [typically Channel 3/4] from a VCR is essentially a composite video signal plus FM audio signal, the same as a broadcast signal received at an antenna).

Frame TBCs can eliminate Macrovision if they rebuild the 39 lines of timing information and do not add the Macrovision signal back in. But video capture and recording devices that claim TBC still have to honor Macrovision and typically do so by preventing good capturing.

Also, for a TBC to effectively rebuild the image it has to precisely detect where each line and frame should start working with the analog video signal it receives. Some are much better than others at reading sloppy input signals typical of consumer analog video formats.
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  #6  
02-17-2022, 11:56 AM
Cortez Cortez is offline
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film.jpg

This is what we called film? A single image, field, frame, cell is one rectangle on the picture?

In my language film = movie

Quote:
while TV paints it one scan line at a time.)
It is related to interlacing? Only every second line drawn at a time? So a single image contains only every second line, odd and even lines frame by frame?

Quote:
scan lines
What is a scan line?

Quote:
Frame TBCs can eliminate Macrovision if they rebuild the 39 lines of timing information and do not add the Macrovision signal back in. But video capture and recording devices that claim TBC still have to honor Macrovision and typically do so by preventing good capturing.
So Frame TBC deals only with the non-visible timing and non-image data? It processes it, detects that it has some Macrovision artificial error or any other errors. Maybe it can not distinguish them from each other. Rebuilds that data without the found errors or just doesn't add the Macrovision signal back if it can identify it at all.

This section has timing data as timestamps or something like that? Because VCR can display on the front the timing. My JVC has also this line scale (ruler or something) that show the full tape length and my position. They get these information from this non-visible area?


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02-17-2022, 12:15 PM
cbehr91 cbehr91 is offline
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What drove the point of a frame TBC home for me [I]was[I] audio. I was converting SP VHS camcorder masters and whenever there was a timecode break (a gap in recorded signal on the tape due to the camera being paused or shut off) my captured file lost audio sync and the frame rate of the captured file was not a precise 29.97 fps.

Even using an ES10 fixed audio sync and framerate, but YMMY (your mileage may vary). Basically frame TBC corrects the unseen erratic/chaotic analog signal for your capture device.
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02-17-2022, 12:30 PM
dpalomaki dpalomaki is offline
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- A TV video image is a raster scan comprised of individual lines. Originally they were all interlaced. Interlaced was used to reduce required bandwidth (and cost) while providing smooth motion.
- Two interlaced FIELDS (one with odd lines one with the even lines) are combined to form a complete FRAME (image) but usually spaced in time by 1/2 the frame rate.

Computer images were mainly progressive, each frame is a complete image.

Over time video and computers worlds joined as technology advanced. While VHS and Video8 are always interlaced, modern video from cable boxes, camcorders, files, etc. can be either interlaced or progressive.

A scan line is one line of the video image. Scan is used because that is how it originally was formed, a flying spot moving across the screen. The original analog TV sets formed the image by an electron beam hitting phosphor on the CRT. The beam strength (number of electrons in it) was controlled by the analog video signal. Sent one line at a time.

Frame TBC's come in a wide variety with various features. They store the full frame and then spit out with stable timing. In the simplest incarnation they do not manipulate the visible image portion of the signal. But many may also include built-in processing features such as proc amps that do modify the image.

The non-visible portion of the frame may carry time code, closed captions, and similar information. Different VCRs may or may not read/interpret this information, and different TBC may or may not preserve it. Some VCR's may judge position on tape by counting tracking pulses and/or speed of supply and take-up reels.

Macrovision came about as a means of copy protection because the developer was able to exploit a "loophole" in VCR electronics design wherein recording the signal to another VCR was inhibited but most TV sets would ignore the signal.

(Interesting that today cable set top boxes will dumb down the component video signal to SD to prevent people copying a HD program using component capable HR capture cards. Content protection is part of why modern BD players do not include component video outputs.)
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  #9  
02-18-2022, 02:04 AM
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lordsmurf lordsmurf is offline
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Movies are known as "films" because those were shot on film.
Film = what you put into a camera before digital era. But film for movies, not still photo cameras.
Film is optical.

Videotapes are not film. Videotape is magnetic media.

Frames TBCs have a relation to audio in a single sense: bad video will dropped frames, but audio doesn't stop. It skews for this reason. The TBC prevents drops, thus audio stays in sync. But frame TBCs were not made for audio, it's just a side effect of the video processing.

ES10/15 is a strong+crippled lines TBC (fails at MV, and other legit errors), with a non-TBC frame sync. So it can still allow audio sync errors. Though far less common than a setup with no TBCs whatsoever.

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