is it normal that DVD CIF is really sharper than VHS??

[anonymoustly]

Can anyone post some pictures?


And do VHS recorders sometimes add blur when downconverting from 720x576 to 352x288 resolution to reduce aliasing effects? That's what I can reason.

look at the photo frame near the candles, with DVD CIF you can see the dots, with VHS only a blurry spot.

DVD CIF (352x288 pixel)

[Attachment 71599 - Click to enlarge]
VHS 240 lines NTSC

[Attachment 71600 - Click to enlarge]

[dannyboy48888]

They may have the same dots but VHS slp has way less color info. If you to a DVD 720x480 and a VHS sp 720x480 they would both have enough color info to look more similar after downscaling.

[anonymoustly]

VHS sp 720x480???

VHS has only 240 lines NTSC or 288 PAL.

[pandy]

VHS sp 720x480???

VHS has only 240 lines NTSC or 288 PAL.

Single track on video tape has full video frame (two fields) - resolution (described in lines for analog signal) is limited but this is horizontal not vertical resolution.

Obviously DVD CIF is sharper as luma bandwidth is 13.5MHz/4 and chroma bandwidth is 13.5MHz/8 - for VCR standards usually bandwidth for luma is around 3MHz and for chrominance it way lower, slightly above 600kHz.

[anonymoustly]

Strange no the qaulity is swapped.

DVD CIF

[Attachment 71602 - Click to enlarge]
VHS PAL

[Attachment 71603 - Click to enlarge]


and what are this shadows? (VHS, not on the DVD CIF version)

[Attachment 71604 - Click to enlarge]

[pandy]

and what are this shadows? (VHS, not on the DVD CIF version)

[Attachment 71604 - Click to enlarge]

this is luminance/chrominance misalignment - common for analog video where luminance signal and chrominance signal are processed separately - due different bandwidth (and as such time delay a.k.a. group delay) frequently luminance and chrominance signals can be shifted - luma/chroma delay.
Also effect can be emphasized if luminance processing circuitry use some form of TI (transient improvement) only for luminance (LTI) but not for color transient improvement (CTI).

[anonymoustly]

is there somewhat i can do too prevent that?

[Skiller]

You are comparing digital pixels with analog lines of resolution (and the underlaying frequency response).
The two cannot be compared easily.
Also note that "lines of resolution" is a measurement of horizontal resolution (as in how many colums can be resolved). And it is adjusted for a 1:1 aspect ratio, not the whole screen which would be 4:3 in most cases.

You do need more than CIF to store all information there may be on VHS. For a start, VHS stores both fields, so you need interlace, which CIF doesn't have.

[lordsmurf]

VHS sp 720x480???
VHS has only 240 lines NTSC or 288 PAL.

You're mixing up the axis.
VHS = ~240x480 (or more, or less, depending on factors)
CIF = 352x240

But the comparisons are entirely invalid, as both very obviously originate from different sources. There is obvious generational loss in the VHS (note chroma offset, ringing/halo), but the VCD is from clean source. A low-end VCR does not help matters.

However, that said, I see bad deinterlace loss in the stills, so "better" is arguable.

[anonymoustly]

Hello the vhs is recorded on the PC with OBS from a component (yellow) RCA cable.
The VHS is recorded from 1080p file (blu-ray player device) from component (yellow cable)

The CIF DVD is from 1080p file, i have notting to do here with VCD

But can anyone put a video on VHS and DVD CIF and post screenshots? Thanks,

[anonymoustly]

VHS sp 720x480???
VHS has only 240 lines NTSC or 288 PAL.

You're mixing up the axis.
VHS = ~240x480 (or more, or less, depending on factors)
CIF = 352x240

But the comparisons are entirely invalid, as both very obviously originate from different sources. There is obvious generational loss in the VHS (note chroma offset, ringing/halo), but the VCD is from clean source. A low-end VCR does not help matters.

However, that said, I see bad deinterlace loss in the stills, so "better" is arguable.

240x480???

Do you not mean: 480x240??

[Sharc]

and what are this shadows?

These bright contours around objects edges are halos. Usually caused by the ringing of (over-)sharpening filters. Switch off any sharpeners of your VHS player. Usually these sharpeners do more harm than good.
Halos can be 'fixed' to some extent in post processing (Avisynth), accepting some other compromise. Therefore it is better to avoid these from the beginning.
For a valid comparison you would have to capture the VHS decently (lossless interlaced, 720x480), then deinterlace it decently (off line) and eventually resize it.

[anonymoustly]

Can anyone recorded this movie on VHS and get to video file and/or post results?
Thanks,

[anonymoustly]

and what are this shadows?

These bright contours around objects edges are halos. Usually caused by the ringing of (over-)sharpening filters. Switch off any sharpeners of your VHS player. Usually these sharpeners do more harm than good.
Halos can be 'fixed' to some extent in post processing (Avisynth), accepting some other compromise. Therefore it is better to avoid these from the beginning.
For a valid comparison you would have to capture the VHS decently (lossless interlaced, 720x480), then deinterlace it decently (off line) and eventually resize it.

And where it is? I do not have the VCR anymore, but it was a Zenith VRD210. I canot find manual for this.

[Sharc]

Can anyone recorded this movie on VHS and get to video file and/or post results?
Thanks,

When you transfer (record) this clip onto VHS (analog realm) the quality will always be lower than when you downsize it directly in the digital realm.

[lollo]

240x480???

Do you not mean: 480x240??

Read again post #8 https://forum.videohelp.com/threads/409943-is-it-normal-that-DVD-CIF-is-really-sharper...HS#post2693107, everything is explained there.

Analog signal has no pixels, but 576 lines containing video information for PAL (480 for NTSC). Inside each line you can distinguish different "elements" in relation to the bandwidth in use (frequency).

VHS has no pixels. When you digitize an Analog signal from VHS you use 576 pixels for vertical resolution (corrisponding to the number of lines in the analog domain) and a certain amount of number of pixels for horizontal resolution. The choice is 720, as per ITU-R BT.601-4 (formerly "CCIR-601" or "Rec.601") specification, even if the number of "elements" you can distinguish in a VHS line is not that big, but is rather lower, 400 or less for S-VHS, 340 or less for VHS.

The 720 pixels inside a line are then "expanded" to 768 when displaying in accordance to 4:3 DAR (display apect ratio).

[anonymoustly]

can anyone record the sample on VHS and post photo/screenshot?

[Skiller]

A properly recorded VHS tape played back on a good working deck is going to look better than CIF resolution.*

*Edit: Except for the chrominance, but unless it's animation and computer graphics, this is not too obvious.

The choice is 720, as per ITU-R BT.601-4 (formerly "CCIR-601" or "Rec.601") specification, even if the number of "elements" you can distinguish in a VHS line is not that big, but is rather lower, 400 or less for S-VHS, 340 or less for VHS.

This.

Furthermore, it is important to understand that you need much more than ~340 digital pixels to sample and store that potential. Otherwise, this would result in aliasing – or blurring.
If you look at Kell factor, you will find that approximately 0.7 times the pixel count is the amount of detail that is actually resolved without aliasing.
Thus, 340 : 0.7 ≈ 485
So you need roughly a digital frame size of ~485x576 to store all information there may be in a really good VHS recording.
352x288 is nowhere near enough, although it does not show well with bad recordings played, captured, processed and encoded in an iffy way.

[lollo]

Yes Skiller, I did not want to enter into technical details with Nyquist–Shannon sampling theorem and Kell factor. Even because, with all respect to his aptitude, I suspect OP is more interested in practical results than understanding the theory behind; he's keep asking external experimets.

[Skiller]

If I was bored, I'd do the experiment the OP is asking. But we know the outcome and the theory behind it. So there is no point, although the experiment itself can be fun to do.

The real question the OP should ask him/herself, in my opinion, should be: Does CIF resolution look good enough to me?

Then there is the question why anyone would want to use CIF resolution for anything in 2023 considering the alternatives...

[anonymoustly]

VHS original screencap

[Attachment 71615 - Click to enlarge]
VHS to Digital screencap

[Attachment 71614 - Click to enlarge]
Composite from 1024x576 DVD (seperate MPEG file, not DVD standard 720x576)

[Attachment 71616 - Click to enlarge]

It seems most of shapness already lost at the VHS recording. And not at the TV capture card.
The Digital VHS copy very grainly and also MPEG blocks, however the bitrate is very high.

[Skiller]

It seems most of shapness already lost at the VHS recording.

Yes, of course.

I noticed your VCR needs a heads cleaning procedure (or at least a cleaning tape). The first photo shows the typical comet-like drop outs of dirty video heads.
Other than that, you are probably asking for too much with a standard VCR connected to a modern TV. That combination is going to look bad in any case.

[pandy]

The 720 pixels inside a line are then "expanded" to 768 when displaying in accordance to 4:3 DAR (display apect ratio).

nope - you are confusing two different things - 720 pixels (in fact usually less, around 716 pixels max for NTSC and around 706 pixels max for PAL) occupy full line time and they are not expanded to 768 pixels - different video formats using different sampling frequencies - ITU sampling rate is 13.5MHz where older analog/digital pre ITU video systems usually use 4fsc (4 times chrominance subcarrier - for NTSC fsc is approx 3.58Mhz and for PAL is 4.43MHz) frequency as sample rate - this give 720 vs 768 pixels.
And real display aspect ratio depend on many factors related to CRT technology (and video tubes if camera using video tube technology).

[lollo]

Once digitized the frequencies are not relevant anymore; the stored PAL signal is 720x576 pixels (only 702/704 in reality, but that's another story) at a frame rate of 50 fields per second. The 720 pixel will then display on modern TV and Monitors as 768x576 in accordance to 4:3 DAR.

[lollo]

It seems most of shapness already lost at the VHS recording.

An introduction to some concepts in this basic and old guide if you wish to read http://www.doom9.org/index.html?/capture/introduction.html

The Digital VHS copy very grainly and also MPEG blocks

MPEG2 has a difficult task with noise, even at high bitrate. Best approach is some AviSynth processing on the capture involving a bit of "restoration" prior to encoding

[pandy]

Once digitized the frequencies are not relevant anymore; the stored PAL signal is 720x576 pixels (only 702/704 in reality, but that's another story) at a frame rate of 50 fields per second. The 720 pixel will then display on modern TV and Monitors as 768x576 in accordance to 4:3 DAR.

how it will suddenly get those missing pixels? - there is no such thing as 768x576 in PAL - total video line in PAL is 64us long, line blanking interval is somewhere around 12..11.7us i.e. active video line is between 52..52.3us and as pixel sample rate is 13.5MHz (i.e. pixel time 74.074ns) so 52.3us/74.074ns is approximately 706 pixels - there is no place for 768 pixels there unless you are using higher sample rate (around 14.436MHz) but then you are not ITU.

and frequencies are very important - digitized or not...

[Bwaak]

the number of "elements" you can distinguish in a VHS line is not that big, but is rather lower, 400 or less for S-VHS, 340 or less for VHS.

Early Umatic machines were spec'd both for color (250 TVL or so) and monochrome (320 TVL). Later SP models were only spec'd for color (250-260 TVL), I suppose because in the 1980s most people replaced their BW TVs with color sets, so no one cared for monochrome content.

VHS usually was spec'd for color only, and in color mode luma resolution is 240-250 TVL. Sure, it should be higher in monochrome mode, I guess about the same as Umatic, but considering that Umatic is only 320, I have a hard time believing VHS resolving 340. I wonder whether SVHS has significantly higher resolution in monochrome mode compared to color mode, for which 400 TVL is spec'd.

Anyway, for color video horizontal resolution of VHS is 250 lines max, which considering Kell factor brings it to 360 samples needed to present it, so if I understand it correctly, CIF should be ok for resolving horizontal detail, but halved number of scanlines limits vertical resolution.

[lollo]

how it will suddenly get those missing pixels?

it is square pixel concept, pixel aspect ratio and display aspect ratio relations. Extrapolated to full HD or higher resolution monitors.

and frequencies are very important - digitized or not...

They do not exist anymore in the digitized frame.

Anyway, for color video horizontal resolution of VHS...

Yes, Bwaak, I took numbers for luminance (Y) only, to make it simpler.

[Skiller]

@ Bwaak

I have a hard time believing VHS resolving 340.

TVL (or "lines of resolution" as I called it in post #8) is adjusted for a square, 1:1 aspect ratio screen area. Thus, to get the resolution across an entire 4:3 image, TVL needs to be multiplied by 4:3. Then you apply Kell factor, if needed.
Why is that? I don't know, TVL is a weird measurement anyways.

On Wikipedia it says:

A resolution of 400 TVL means that 200 distinct dark vertical lines and 200 distinct white vertical lines can be counted over a horizontal span equal to the height of the picture.

250 TVL * 1.33 = 333 (roughly the number of 340 lollo quoted)


333 : 0.7 = ~475-485 horizontal pixels needed to store all information there may be in VHS (under ideal conditions).

[lollo]

250 TVL * 1.33 = 333 (roughly the number of 340 lollo quoted)

yes

333 : 0.7 = ~475-485 pixels to store all information there may be in VHS

Equivalent resolution for interlaced material. I am not sure if for "progressive" video (telecine, with the two fields coming from the same moment in time) the same applies, I suspect not.