Is lossless really necessary?

[sophisticles]

I don't want to muck up the other thread:

https://forum.videohelp.com/threads/413554-Deinterlacing-in-2024

So I am dedicating this one to investigating whether capturing to lossless, or even including it anywhere in the workflow of any video project, is actually necessary or if it even makes a bit of difference.

The source for this test is a roughly 300mb, just under 21 seconds, 12-bit, xyz, jpeg2000, mxf that was made by the Tears of Steel team as a way of testing Digital Cinema media server, the computers used to show digital movies in theaters. I wanted to attach it but mxf is not an permitted upload format. You can get it from here:

http://download.blender.org/mango/dcp/tos_dcp_test_04.zip

This file is very difficult to work with, consumer grade computers do not have hardware decoding for this format and I do not have a computer powerful enough to play this back at normal speed via CPU.

I transcoded this to the following formats using Shotcut:

FFV1, 10-bit, mlt_image_format=rgb, pix_fmt=yuv444p10le, lossless, took 4:08 to create and is 3.6gb

ProRes HQ, 10-bit, mlt_image_format=rgb, pix_fmt=yuv422p10le, took 2:49 to create, and is 2.5gb

I then created three different AV1, 2-pass, 5mb/s, 8-bit, 4:2:0 files, one was created from the FFV1 source, one was created from the ProRes source and one was created by converting the ProRes to 10-bit HEVC and using this as the source.

Can anyone really tell the difference between the final encodes?

If not, then lossless is a complete waste.

[Alwyn]

That ZIP link goes nowhere.

[sophisticles]

That ZIP link goes nowhere.

It's not supposed to go anywhere, it's the direct download link.

Clicking on it should download a file named tos_dcp_test_04.zip.

[Alwyn]

Nothing's happening here. When I click it, my Chrome screen flashes and that's it. No redirect to Blender and no direct downloading commences.

I suggest you put it on Google Drive.

[lollo]

When capturing VHS lossless is necessary because:
- the media by nature is problematic, suffering of high noise and chroma shift; no codec likes that
- the media by nature is interlaced, better to do not risk bad field manipulation while capturing with a lossy codec
- a “processing” is always needed, at minimum to hide/remove the head switching noise, there is no sense then to do not capture lossless
- any post-processing requires a lossy decode operation if the captured stream is not lossless
- the is no “capture for archiving” and “capture for distribution”, you just capture once, and that being lossless
- a real time capture is a “continuos time” process, better to do not add unnecessary tasks like compressing in real time to avoid dropped and/or inserted frames
- the media is prone to introduce asynchronous audio and video, better to do not add codec variable in the equation
- lossless capture is nice and well established since decades with adequate workflows to produce outstanding results
- whatever other reason I forgot to write here in this quick reply on my phone

So, once more, and like the other recent thread on “is upscale necessary?” another complete non sense of yours

[lollo]

On top of that, reading what you write and wrote recently on the subject, I am sure you never captured a VHS in your live!

[dellsam34]

Capturing any analog video tape media not just VHS, is a process not a simple conversion, So the lossless the first captured file, the better looking the final file. The OP has entered an uncharted territory and he is getting lost, Instead of asking questions to learn, he pretends to know it all and arguing with anyone dare to question his knowledge. We are all learning here, no exceptions, every single one of us lacks knowledge in certain areas at any moment of our lives, No one knows it all.

[pandy]

Nothing's happening here. When I click it, my Chrome screen flashes and that's it. No redirect to Blender and no direct downloading commences.

I suggest you put it on Google Drive.

Works for me - i suggest check your Chrome configuration - perhaps popups are disabled by default or there is some other protection active (maybe AI driven to release you from pain of talking decisions and protect you from your own actions - yes, this was intentionally a bit sarcastic)

[dellsam34]

Yes, ad removers do block the pop ups. Right click on the link, select save as and choose to keep the file when asked to delete it.

[Alwyn]

Arr, OK, yes, that's probably it. Could've just attached the ZIP file here.

[sophisticles]

When capturing VHS lossless is necessary because:
- the media by nature is problematic, suffering of high noise and chroma shift; no codec likes that

I need you to think rationally for a second. You admit that the media is problematic by nature and suffers from high noise and chroma shift, why are you determined to capture all those issues?

Why do you want to capture high noise and chroma shift?

Why would you not want to capture to a high quality codec that can potentially remove that noise during the capture?

- the media by nature is interlaced, better to do not risk bad field manipulation while capturing with a lossy codec

Why not capture it post TV, after the TV has already deinterlaced it?

In other words capture from the TV using a screen recorder?

I doubt that a software deinterlacer is going to do a better job than a hardware deinterlacer built into a TV specifically for that purpose.

- a “processing” is always needed, at minimum to hide/remove the head switching noise, there is no sense then to do not capture lossless

It makes sense because lossless is always significantly larger file sizes and you should be using RAID to capture.

As I have pointed out, lossless isn't even used in professional movie and TV production.

- any post-processing requires a lossy decode operation if the captured stream is not lossless

The difference between lossless and near lossless is imperceptible in practice, as I showed with my test encodes, unless you use metrics like PSNR,

More importantly, as was pointed out in the other thread, many NLEs seem to have a problem with lossless files, there is a reason why ProRes and DNxHD are industry standards.

- a real time capture is a “continuos time” process, better to do not add unnecessary tasks like compressing in real time to avoid dropped and/or inserted frames

Hate to break this to you, but unless you capture lossless using a RAID0 array, you are most likely dropping frames.

- the media is prone to introduce asynchronous audio and video, better to do not add codec variable in the equation

Not really an issue, you can always separate the audio and video streams via demuxing and you can easily correct sync issues.

Not to mention that these happen with lossless capture as well, due to people not having computers powerful enough for lossless capture.

- lossless capture is nice and well established since decades with adequate workflows to produce outstanding results

You're kidding, right?

Outstanding results? There are literally thousands of posts here and on other forums of people asking how to fix problems with their captured video.

Furthermore, just because something has been done for decades doesn't mean there is no better way. Cars used carburetors and OHV designs for decades, then they started using mechanical fuel injection, then throttle bodies, then electronic fuel injection and we have hybrid engines with overhead cams, multiple valves, turbos, etc.

It's called improving on what was.

It also implies that people got the process right the first time and that there is only on correct process to be used.

I disagree with that and think people need to try different ways.

- whatever other reason I forgot to write here in this quick reply on my phone

Wow, this post triggered you so bad that you needed to respond on your phone?

LOL.

So, once more, and like the other recent thread on “is upscale necessary?” another complete non sense of yours

While you may find it "nonsense", I can guarantee you that someone will stumble on that thread and rethink their plans of upscaling a video.

One more thing, if you would "educate" an ignoramus like myself, which the one true lossless codec that must be used?

Should we use 8-bit utvideo?

How about lossless AVC?

Lossless HEVC?

How about 12-but 4:4:4 AV1?

What does the gospel according to lollo say?

[sophisticles]

On top of that, reading what you write and wrote recently on the subject, I am sure you never captured a VHS in your live!

I haven't done a VHS capture in 30 years, I admit that.

But I also would not capture the way you guys are capturing.

What I would do is use a screen recorder like one of these:

https://www.amazon.com/TV-Screen-Recorder/s?k=TV+Screen+Recorder

Reading through all the various threads here, and looking at all the samples and pictures have convinced me that people have adopted a set of procedures that are not based on anything else other than "this is the way it's always been done".

At some point, decades ago, some anonymous cult of personality declared "this is the nest way to digitize VHS", it became gospel and everyone has followed it without daring to question the wisdom.

Based on the threads I see here and on other forums, I am convinced people need to explore other options and different workflows.

[dellsam34]

Why would you not want to capture to a high quality codec that can potentially remove that noise during the capture?

That's a terrible idea, You just baked in your files, captured files should be untouched so when you don't like the result you can go back to the original files and make another attempt or other adjustments, Analog tape format cannot be solved by capturing into a lossy codec, stop arguing stuff you don't understand, You don't know what you don't know.

What I would do is use a screen recorder like one of these:

https://www.amazon.com/TV-Screen-Recorder/s?k=TV+Screen+Recorder

Sure, let us know how it works out for you.

[usually_quiet]

Why not capture it post TV, after the TV has already deinterlaced it?

In other words capture from the TV using a screen recorder?

I doubt that a software deinterlacer is going to do a better job than a hardware deinterlacer built into a TV specifically for that purpose.

What you are proposing cannot work. A screen recorder can capture the results of video processing that is taking place inside a computer but it can't capture the results of video processing that is taking place inside a TV.

A Tablo also won't work. A Tablo is a digital video recorder. It captures a digital video stream from broadcast TV. A capture device won't work either because it captures video coming into a TV not the results of video processing going on inside the TV.

[Sharc]

I haven't done a VHS capture in 30 years, I admit that.

That says it all

[sophisticles]

Why not capture it post TV, after the TV has already deinterlaced it?

In other words capture from the TV using a screen recorder?

I doubt that a software deinterlacer is going to do a better job than a hardware deinterlacer built into a TV specifically for that purpose.

What you are proposing cannot work. A screen recorder can capture the results of video processing that is taking place inside a computer but it can't capture the results of video processing that is taking place inside a TV.

A Tablo also won't work. A Tablo is a digital video recorder. It captures a digital video stream from broadcast TV. A capture device won't work either because it captures video coming into a TV not the results of video processing going on inside the TV.

Please explain further why it can not work.

I can connect a VCR to a TV.

The TV will deinterlace the input and display it.

I can connect another TV that will also display the same thing.

Why can i not capture the signal going between the two TVs?

For example, I can use a device like this to show the same input on two TVs:

https://www.pacroban.com/blogs/news/how-to-connect-two-tvs-together

Why can I not attach an HDMI capable capture device in place of a second TV and capture a hardware deinterlaced signal?

I ask because years ago i used to capture OTA and cable programs using an AIW 9700 Pro and the deinterlacing was fine.

I also can not wrap my head around why anyone would capture VHS, which is 320x480 to 720x480, where do they think these extra 400 pixels are coming from?

In addition they capture lossless so they can preserve all the blemishes, noise, static, chroma issues, everything and then bang their heads against the wall trying to fix the capture.

Maybe the other poster is right, maybe i don't know what i am talking about.

But i can tell you that i would be trying to capture a post-TV signal at native resolution and using a codec that minimizes any blemishes, not preserves them for posterity.

That's just me.

[lollo]

Wow, this post triggered you so bad that you needed to respond on your phone?

LOL.

No, you do not have that power. Not even your ignorance on the subject (which is at top here) can have such an effect on me. I am just travelling without my PC.

About all the rest, sorry, even if I appreciate your attempt to reply with "some sort of facts" I have no intention to reply and lose any time with your complete non sense.

To the next

[Sharc]

I also can not wrap my head around why anyone would capture VHS, which is 320x480 to 720x480, where do they think these extra 400 pixels are coming from?

VHS is an analog medium. It doesn't have a horizontal resolution of 320, but nil useful above. The transition is gradual and even tape dependent. It is therefore essential to capture the signal above 320 as well, because in post processing that information is essential for a good picture restoration by means of digital signal processing. Similar is known from the restoration of dull old audio tapes.

Regarding lossless codecs: Lossless is lossless, irrespective of the codec. There is no such thing like better or worse lossless. The question whether lossless is really necessary is the same as asking whether lossy is good enough .....

[lordsmurf]

I haven't done a VHS capture in 30 years, I admit that.

I guarantee you didn't capture anything in 1994.

I also can not wrap my head around why anyone would capture VHS, which is 320x480 to 720x480, where do they think these extra 400 pixels are coming from?.

320x480 isn't a legal resolution.

Maybe the other poster is right, maybe i don't know what i am talking about.

Correct.

[sophisticles]

I also can not wrap my head around why anyone would capture VHS, which is 320x480 to 720x480, where do they think these extra 400 pixels are coming from?

VHS is an analog medium. It doesn't have a horizontal resolution of 320, but nil useful above. The transition is gradual and even tape dependent. It is therefore essential to capture the signal above 320 as well, because in post processing that information is essential for a good picture restoration by means of digital signal processing. Similar is known from the restoration of dull old audio tapes.

Regarding lossless codecs: Lossless is lossless, irrespective of the codec. There is no such thing like better or worse lossless. The question whether lossless is really necessary is the same as asking whether lossy is good enough .....

So you are saying this is not correct:

https://en.wikipedia.org/wiki/VHS

https://en.wikipedia.org/wiki/Television_lines

https://www.mediacollege.com/video/format/vhs/

https://www.canada.ca/en/conservation-institute/services/conservation-preservation-pub...apes.html#a2a1

Everything I can find says that VHS has a maximum of 240 lines of horizontal resolution, though there is a slightly higher quality version at 250 lines.

So the obvious question becomes what signal is being captured above the 240 lines?

You can't capture what is not there.

Regarding lossless codecs: Lossless is lossless, irrespective of the codec. There is no such thing like better or worse lossless. The question whether lossless is really necessary is the same as asking whether lossy is good enough .....

You are sadly mistaken and it is very easy to prove that you are mistaken.

Consider the source I linked to at the start of the thread, it is a 12-bit, 4:4:4, XYZ, JPEG2000, it is mathematically impossible to lossless represent it with an 8-bit 4:2:2 "lossless" codec like utvideo.

There's a reason why there is 10-bit 4:4:4 lossless, 10-bit 4:2:2 lossless, etc.

And yes, fundamentally I am asking if visually lossless lossy is good enough.

Forget about ProRes and DNxHR for a minute, is 10-bit x264 crf 5 Intra or x265 12-bit 4:4:4 crf 5 Intra good enough?

How about 12-bit 4:4:4 AV1 crf 5 Intra, is utvideo or huffy really better?

I think a lot comes down to inertia caused by an adherence to legacy methodologies and a fear of trying different ways.

[Sharc]

I also can not wrap my head around why anyone would capture VHS, which is 320x480 to 720x480, where do they think these extra 400 pixels are coming from?

VHS is an analog medium. It doesn't have a horizontal resolution of 320, but nil useful above. The transition is gradual and even tape dependent. It is therefore essential to capture the signal above 320 as well, because in post processing that information is essential for a good picture restoration by means of digital signal processing. Similar is known from the restoration of dull old audio tapes.

Regarding lossless codecs: Lossless is lossless, irrespective of the codec. There is no such thing like better or worse lossless. The question whether lossless is really necessary is the same as asking whether lossy is good enough .....

So you are saying this is not correct:

https://en.wikipedia.org/wiki/VHS

https://en.wikipedia.org/wiki/Television_lines

https://www.mediacollege.com/video/format/vhs/

https://www.canada.ca/en/conservation-institute/services/conservation-preservation-pub...apes.html#a2a1

Everything I can find says that VHS has a maximum of 240 lines of horizontal resolution, though there is a slightly higher quality version at 250 lines.

So the obvious question becomes what signal is being captured above the 240 lines?

You can't capture what is not there.

Regarding lossless codecs: Lossless is lossless, irrespective of the codec. There is no such thing like better or worse lossless. The question whether lossless is really necessary is the same as asking whether lossy is good enough .....

You are sadly mistaken and it is very easy to prove that you are mistaken.

Consider the source I linked to at the start of the thread, it is a 12-bit, 4:4:4, XYZ, JPEG2000, it is mathematically impossible to lossless represent it with an 8-bit 4:2:2 "lossless" codec like utvideo.

There's a reason why there is 10-bit 4:4:4 lossless, 10-bit 4:2:2 lossless, etc.

And yes, fundamentally I am asking if visually lossless lossy is good enough.

Forget about ProRes and DNxHR for a minute, is 10-bit x264 crf 5 Intra or x265 12-bit 4:4:4 crf 5 Intra good enough?

How about 12-bit 4:4:4 AV1 crf 5 Intra, is utvideo or huffy really better?

I think a lot comes down to inertia caused by an adherence to legacy methodologies and a fear of trying different ways.

Nonsense. You are wildly mixing the capturing of an analog signal (which is neither 8bit nor 12bit nor 20bit nor 4:4:4:4 nor 4:2:0 nor xxx pixels nor does it "have" 320 lines maximum or whatever, and its conversion to a digital format ("digitization"), with re-encoding of an already digital source. And you are not clear about the meaning of lossless encoding of a given digital source which may already be lossy compared to the original analog or digital master.

[usually_quiet]

Why not capture it post TV, after the TV has already deinterlaced it?

In other words capture from the TV using a screen recorder?

I doubt that a software deinterlacer is going to do a better job than a hardware deinterlacer built into a TV specifically for that purpose.

What you are proposing cannot work. A screen recorder can capture the results of video processing that is taking place inside a computer but it can't capture the results of video processing that is taking place inside a TV.

A Tablo also won't work. A Tablo is a digital video recorder. It captures a digital video stream from broadcast TV. A capture device won't work either because it captures video coming into a TV not the results of video processing going on inside the TV.

Please explain further why it can not work.

I can connect a VCR to a TV.

The TV will deinterlace the input and display it.

I can connect another TV that will also display the same thing.

Why can i not capture the signal going between the two TVs?

For one thing, TVs don't provide HDMI-out for video so there is nothing to capture. (HDMI ARC and eARC connections can provide audio output for a receiver) If you mean a SCART analog connection, which allows daisy-chaining equipment, I think that is implemented using an internal splitter, which means the SCART-out signal passed along by the first TV to the second TV is unprocessed. A few analog TVs had a composite video "monitor out" connection but composite video only supports an interlaced signal.

For example, I can use a device like this to show the same input on two TVs:

https://www.pacroban.com/blogs/news/how-to-connect-two-tvs-together

Why can I not attach an HDMI capable capture device in place of a second TV and capture a hardware deinterlaced signal?

De-interlaced by what? HDMI splitters don't ordinarily deinterlace or change the signal resolution. They merely create two output signals that are identical to the input.

There are HDMI video scalers that are able to deinterlace video and change the resolution but only expensive ones do a half-way decent job.

I ask because years ago i used to capture OTA and cable programs using an AIW 9700 Pro and the deinterlacing was fine.

I never owned any of the AIW's. I only know that in addition to analog video inputs, they were equipped with an analog tuner for analog OTA TV and cable TV signals, plus a video graphics adapter. Someone else will need to tell you if, how, and when it performs deinterlacing.

I also can not wrap my head around why anyone would capture VHS, which is 320x480 to 720x480, where do they think these extra 400 pixels are coming from?

720x480 or 704x480 or 640x480 are merely convenient resolutions that correspond to common standards in the digital world. The horizontal resolution used for digital captures is produced by sampling the analog signal.

[dellsam34]

Mr Sophisticles stop sailing against the wind, As I explain before you don't know what you don't know, What you are doing is exactly similar to a plumber arguing with a doctor about a complicated medical procedure. You don't know how VCR works, you don't know that there is a standard governs the capturing of analog video into digital, you probably never heard of rec.601 until you read it somewhere here, You don't know that 720x486 (later simplified to 480) 4:2:2 for NTSC is a standard not a choice, You probably don't know that all capture cards except the cheap fake chinese ones you are linking, adhere to that same standard, and I don't know all the things you don't know, so I just listed few, So please stop, go read some materials, there are plenty of books and white papers about the subject, read them and stop assuming that if something you don't know that means it doesn't exist or it is not true.

[sophisticles]

I guarantee you didn't capture anything in 1994.

How do you guarantee it?

How do you know what I have captured in my life?

320x480 isn't a legal resolution.

You are correct, there are either 240 or 250 horizontal lines, so then why are you capturing at 720x480?

What information do people think is being captured by the extra resolution?

[sophisticles]

Nonsense. You are wildly mixing the capturing of an analog signal (which is neither 8bit nor 12bit nor 20bit nor 4:4:4:4 nor 4:2:0 nor xxx pixels nor does it "have" 320 lines maximum or whatever, and its conversion to a digital format ("digitization"), with re-encoding of an already digital source. And you are not clear about the meaning of lossless encoding of a given digital source which may already be lossy compared to the original analog or digital master.

It is an analog signal that has a finite amount of information and a finite physical size.

There a finite number of lines displayed when the analog signal is displayed on a digital display, specifically either 240 or 250 lines.

This regards to color information, there is a limited amount of that as well, and it can be represented with a finite amount of precision.

Using your argument, one might as well capture VHS to 12k RGBA.

[poisondeathray]

You are correct, there are either 240 or 250 horizontal lines, so then why are you capturing at 720x480?

What information do people think is being captured by the extra resolution?

To reduce aliasing. You need ~ 2x the samples

Meet Mr. Nyquist

https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem

It's just like audio samples - (good) human hearing at young age (before too many rock concerts) might be up to ~20Khz , so typical distribution formats use roughly double that at 44.1Khz or 48Khz

And yes, fundamentally I am asking if visually lossless lossy is good enough.

It depends on the scenario , and criteria.. obviously. If you're looking at the end of a lower quality distribution format , it's usually more than good enough.

Is a Ferrari "good enough" for you ? Maybe a Kia is ok ? - Lots of subjectivity there

ProresHQ wasn't good enough for some DP's , Producers - and they complained that's why Prores XQ4444 was introduced - that's the true history behind XQ4444. The complaint was added noise from ProresHQ, and for times you needed full color .

For some scenarios - high end intermediate VFX pipelines - None of them - ProresHQ or XQ4444/Cineform/x264/x265 etc...are good enough - They are never used at all. 10 or 12bpc is not enough. Only 32bit EXR is used. Prores is only used near the end of the pipeline near delivery

Forget about ProRes and DNxHR for a minute, is 10-bit x264 crf 5 Intra or x265 12-bit 4:4:4 crf 5 Intra good enough?

Nice that you bring that up - x264 10bit 422 intra is fully adjustable, you can get about 10-20 db PSNR higher than ProresHQ at qp1, if ProresHQ wasn't "good enough" . It doesn't get mishandled like codecs in lossless mode either in many programs like NLE's. You have field order, SAR (aspect ratio) signalling.

[oln]

Again analog "lines of resolution" is not the same as digital horizontal resolution. Capturing is done at 720 pixels horizontal as that's what all capture devices capture analog SD video at due to standardization. Some older ones may let you grab a scaled down version but then you are relying on the limited hardware in the capture device to do that well.

I feel you are trying to apply the same processes you would use for content coming from a modern camera or render to analog video archiving but those things are very different. Modern HD content is a very different beast to a VHS tape where the resolution is extremely limited as is and you don't want to throw away anything more than needed if the goal is to actually preserve it. Your comparison of a HD render here isn't very relevant.

We also don't have really the luxury of an abundance good hardware and software that would do a proper job of doing the processing of the video in an automated fashion as you are hinting at. I think it would be fine to capture using a high quality near lossless format but the software support for that is a bit limited (even like blackmagic's bundled software can only do that on macos for whatever reason...). If you capture to a lossy format noise and blotches aren't "removed", it ends up as macroblocking and worse noise which makes it harder to deal with down the line, not to mention issues if interlacing isn't properly handled.

Like I wish there was a simple device that would work like these boxes that you put a sd card into that actually had a decent video decoder in it that could stabilized the video properly and output a properly deinterlaced and denoised 59.94 or 50p h.264/or hevc file with proper aspect ration at decent bitrate for the average person to just get their old home videos in a better formats. Sadly all we seem to get are crap that give us wobbly crap bitrate files badly deinterlaced to half framerate.

Part of the reason people are still using old methods for this is that there hasn't been much useful development in this space on either the software or especially the hardware side the last 15-20 years so we're mostly stuck with old software and hardware still.

[lollo]

Using your argument, one might as well capture VHS to 12k RGBA.

Inside the tens of non-sense you wrote, something is true. I think this just happened by coincidence, and not because you know something.

The analog PAL signal (as example) is characterized by 625 lines, 50 interlaced half-frames (or fields) per second, 25 frames per second, and has a bandwidth of approximately 5 MHZ. Note that when speaking of analog signal there is no mention to pixels either in terms of horizontal or vertical resolution, but of bandwidth and number of lines.

The analogue PAL signal must be identified with a waveform (normally a voltage variation over time). This wave, which has its own particular shape, is divided into 625 pieces, which are easily identifiable and can therefore be counted thanks to a series of impulses that mark the beginning and end. Each of these 625 pieces of wave (lasting 64 microseconds) contains information and in particular 576 (does this number sound familiar? ) pieces contain the information, a couple contain test signals, the same number contain teletext information, and others all those synchronisms that allow the TV to know where to draw that line.

For what we are interested in, of the 625 lines of the Pal signal only 576 contain video: what we need to understand is how these lines are organized and what video information they contain. Without going into too much detail, to define what information is contained in a line we need to talk about band.

In practice, an analog video line, which as seen is a small piece of wave, could potentially contain very high information, where by video information we mean the number of points, for example white and black, that I can distinguish on a line: it is clear that if in this line I can insert 1000 distinct white and black points (500 white and 500 black alternating), I have much greater information, in terms of resolution, than if I were able to insert 200 points (100 and 100).

The set of the maximum number of distinct points that I can insert in each line and the number of lines (576 in PAL) define the (analog resolution) of the analog signal: greater (analog) resolution = greater ability to distinguish details in an image.

Considering Shannon's sampling theorem and doing some math, in theory a Pal TV signal at maximum quality (5 MHz band) can allow 384 distinct black/white alternations on one line. Given what has just been said (384 distinct white/black alternations), 768 (does this number sound familiar? ) is the number of samples (pixels) that are able to describe without any loss of quality a PAL analogue signal at maximum quality (5 MHz band).

It means that if I take a line of PAL signal, I digitize it using an A/D converter, transforming it into 768 pixels and then from these 768 I obtain a new analogue line, this is exactly the same as the original line (at least in theory, since it is impossible to do such operations without errors and therefore the introduction of noise and other).
It also means that if I use the same procedure with e.g. 900 points, I always get a row identical to the first, but I simply wasted precious bits. On the contrary, if I use 500 pixels, the line I obtained will not be the same as the original, but will have less details (high video frequencies): from a visual point of view I would have a blurrier line.

768*576 25 frames/sec (does it sound familiar? ) is the "magic" number of pixels after digitalisation that describe a 5 MHz PAL signal without loss of quality. In practice, a video signal, never contains such a high level of information (details, colours, ....) that it requires 768 points for each line, and 720 (does this number sound familiar? ) points are enough to represent the single PAL line of a quality video. Hence the standard ITU-R BT.601-4 (formerly "CCIR-601" or "Rec.601") 720x576.

If instead of a quality PAL signal, we start from a signal stored on a VHS, we could see that 720 is excessive (352x576 is enough, does this number sound familiar? ), but in practice the "Rec.601" standard is used.

So yes, we could "capture" VHS signal at 352x576 without loosing information, but we do not. This is of couse not true for S-VHS and other analog media.

[usually_quiet]

I guarantee you didn't capture anything in 1994.

How do you guarantee it?

How do you know what I have captured in my life?

Hmm... I was an adult in the 1990s. People used to copy their tapes using a second VCR or point a video camera at their TV screen but I don't think that counts as capturing. There was a consumer editing device and software for computers available then that cost thousands of dollars by itself ...not to mention thousands more for additional equipment (not counting the computer). Tapes were used to store the output.

So, now I'm curious... Exactly what method did you use to capture VHS in 1994?

[dellsam34]

Folks, stop feeding the troll. These type of peeps don't get ashamed by making a fool of themselves on the internet as long as they are hiding behind a screen name, I don't know what's the medical name of this disorder.