VCR's TV Tuner -> RCA output - 240 lines ?

[Zetti]

Hi all,

If I use the built-in tuner of my VCR to capture a TV broadcast, and use its RCA output on the back panel to feed the capture card (NO VHS TAPE Recording !) , will the VCR circuit reduce the quality to the VHS standard of the 240 lines ?

Or is this a limitation of the VHS tapes themselves ?

Thanks,

Zetti

[unclebud]

It's the limitations of the tape format. You should be able to get a pretty good picture from a tuner depending on the quality of the VHS deck.

[The_Doman]

No worry about that.
The built in tuners of VHS recorders will give a much higher quality picture then you ever can record to VHS.

I have always used seperate VCR tuners for my TV/Capture cards.
Often the quality is much better then the tuners built on the cards.
Ofcourse some VCR's have better quality tuners built in then others.

[SingSing]

The 240 lines resolution is a VHS limit.

TV tuner output is analog, so it should have the full resolution of the NTSC, plus the analog distortion and noise.

[edDV]

The following is for NTSC (worse case):

The VCR tuner has potential for 4.2MHz (equiv ~330 "lines"* or ~352x480) video luminance bandwidth.

If you record it to VHS luminance gets low pass filtered below 3 MHz (equiv ~240 "lines" or ~ 290x480)

If you pass the tuner to the composite output (E-E mode), the capture card will see 4.2MHz luminance but it must separate Y from C using a Y/C separator.

A simple Y/C separator will do a 3MHz low pass filter for luminance and a 3.1-4.1 notch filter for chroma. The result is again 240 lines.

A fancy Y/C separator will use a comb filter that will extract luminance out to 4.2 MHz (or above for wideband inputs like camcorders).
http://members.aol.com/ajaynejr/vidcomb.htm

For PAL, VHS is still low pass filtered around 3MHz but cheap Y/C separators will low pass filter luminance around 3.7-3.9 MHz (equiv ~300 "lines" or ~360x576). Comb filters will pass luminance out to the limits of the local broadcast (varies ~5-6MHz for PAL or 4.2 MHz for PAL-M).


*"lines" = lines of resolution that can be read on a EIA resolution chart. Figure ~20% more for equivalent pixels.

[The_Doman]

Here a capture from my VCR tuner (analog cable, PAL).
Connected with composite to my Sony D8/DV Camcorder.

[Zetti]

Thanks to everybody that replied,

Well, edDV, so as far as I understood, the equivalent number of lines will be dependent on the frequency, and also dependent on the quality of the devices used, right ?

My set is:

VCR: Samsung SV-5000W to convert on the fly from PAL-M to NTSC
Capture device: Canopus ADVC-100 (DV digitalizer)

How should this set perform ? Equivalent # of lines ?

THANKS VERY MUCH,

Zetti

[The_Doman]

My set is:

VCR: Samsung SV-5000W to convert on the fly from PAL-M to NTSC
Capture device: Canopus ADVC-100 (DV digitalizer)

How should this set perform ? Equivalent # of lines ?

Well you just have to try it out ofcourse.

I have only experience with a Samsung SV-4000W (world wide video) here which I got from a friend because the internal mechanics were broken.

Compared with my other (PAL) VCR's it performed pretty poorly using the tuner or feeding just a video signal through it.

[edDV]

Zetti

I refuse to answer with qualifications for every point on earth until you ID your approximate location and hardware model numbers. Video issues differ by location.

[Zetti]

Thanks The Doman,

I haven't tried it yet, actually I don't have an "issue" here, I'm just willing to learn a bit more;
As far as I understood from your point of view, the quality of the capture will have to do with the tuner quality and doesn't have a direct relation with the so called "VHS resolution of 240 lines", which might then be a limitation of the VHS tape itself, right ?

Considering what edDV said, if the VCR circuit is "good", the equivalent "lines resolution" according to the frequency "passed on" might be around 350 lines, I hope I have understood properly

edDV, I don't understand your point; as I said, I don't actually have an "issue" here, I just want to learn and understand before trying. I've mentioned the models of my VCR and capture device, and said that I wanna use the VCR TV tuner to convert on-the-fly from TV's PAL-M broadcast to NTSC, so I can feed it into the canopus device, as it doesn't accept PAL-M, just NTSC.

Thanks anyway, not only for you and The Doman but to everybody that wrote

Zetti

[edDV]

edDV, I don't understand your point; as I said, I don't actually have an "issue" here, I just want to learn and understand before trying. I've mentioned the models of my VCR and capture device, and said that I wanna use the VCR TV tuner to convert on-the-fly from TV's PAL-M broadcast to NTSC, so I can feed it into the canopus device, as it doesn't accept PAL-M, just NTSC.

Zetti

Zetti, my frustration was from you not identifying your location. These issues differ for every country and TV standard so I feel I have to respond to every possible case. If you are in Brazil then you are in the most confusing place for video.

I missed where you previously mentioned PAL-M and your location is listed as "Earth ... for a while'. Sorry I missed the PAL-M clue.


Brazil uses PAL-M and in some places also uses NTSC.

PAL-M shares all details accept Phase-Alternate-Line color encoding with Americas NTSC-M. As such the vcr tuner would never get more than 330 "lines"* or ~352x480.

Your Canopus ADVC-100 will always capture at 720x480. It has a comb filter so it will extract the full "330 lines" of luminance. It is your choice to encode MPeg2 as 720x480, 704x480 or 352x480.

I would recommend you try encoding the tuner capture at 720x480 and again at 352x480 and see if you notice a difference. If 352x480 looks OK, you can encode to 2-3 hours or more for each DVD.

[trhouse]

edDV's advice to test is good. I recently was looking for an NTSC to VGA converter and tried a Viewsonic N4. It worked but it also degraded the NTSC signal. Even though the Samsung tuner may not, the PAL-M to NTSC converter may reduce your performance.

[edDV]

edDV's advice to test is good. I recently was looking for an NTSC to VGA converter and tried a Viewsonic N4. It worked but it also degraded the NTSC signal. Even though the Samsung tuner may not, the PAL-M to NTSC converter may reduce your performance.

In his case, I'm assuming he is tuning and capturing PAL-M off air from the VCR to the ADVC-100 (DV format 720x480).

According to this chart PAL-M uses 7.5 IRE setup same as NTSC
http://icecube.wisc.edu/~dima/stuff/comp/vstandards.html

So ADVC-100 settings for PAL-M would be

1. Video Format - PAL
2. NTSC Setup - 7.5 IRE

But I'm not sure of that. Experiment.

[trhouse]

I wanna use the VCR TV tuner to convert on-the-fly from TV's PAL-M broadcast to NTSC

If the ADVC-100 accepts PAL-M then the above is not necessary and you would be correct.

[edDV]

I wanna use the VCR TV tuner to convert on-the-fly from TV's PAL-M broadcast to NTSC

If the ADVC-100 accepts PAL-M then the above is not necessary and you would be correct.

wanna use the VCR TV tuner to convert on-the-fly from TV's PAL-M broadcast to NTSC, so I can feed it into the canopus device, as it doesn't accept PAL-M, just NTSC.

Ahh, ok so the ADVC is having trouble with PAL-M.

The multi-system Samsung SV-5000W should be able to convert PAL-M to NTSC easily. It only has to remove the phase reversal every line. Everything else is the same for PAL-M vs NTSC. So the ADVC should be set to NTSC and 7.5 IRE setup. After capture everything will be 480i DV YCbCr format.

[Zetti]

Hi all,

Thanks edDV and everybody that replied, really apreciated;

Yes, I'm in Brazil, my "location" listed on my profile is intended only to be a (not so funny....) joke :P

I've understood so far what you say, all in all I have to decide between two choices:

1) The one listed above, use Samsung's built-in TV tuner to convert on-the-fly the TV broadcast from PAL-M to NTSC and feed it into the Canopus digitalizer (it doesn't get PAL-M, B&W if I try);
I understand by what edDV said that this set up would result in aproximately 330 "lines of resolution";

2) Use the built-in TV tuner of any ATI video card (like any AiW for example, ATI I think is the only one that gets PAL-M) and record it using the HuffYUV codec, then I'd have to forget the DV format. It explains why I've wrote another topic at the "editing" forum that you edDV helped me as well, thanks;

I like to edit my videos, add transitions or so and then on-the-fly MPEG2 isn't a good choice, I'd stick with AVI; but then I have to decide between the DV or HuffYUV options.

People said that the built-in TV tuner of VCR's in general are far better than the ones in the PC video cards, so maybe the 1st choice would be the best bet ?
As a guess, what do you people think would result in a better picture, say equivalent lines of resolution ?

Again, many many thanks not only to edDV but to everybody that have been helping,

Zetti

[Zetti]

I wanna use the VCR TV tuner to convert on-the-fly from TV's PAL-M broadcast to NTSC

If the ADVC-100 accepts PAL-M then the above is not necessary and you would be correct.

wanna use the VCR TV tuner to convert on-the-fly from TV's PAL-M broadcast to NTSC, so I can feed it into the canopus device, as it doesn't accept PAL-M, just NTSC.

Ahh, ok so the ADVC is having trouble with PAL-M.

The multi-system Samsung SV-5000W should be able to convert PAL-M to NTSC easily. It only has to remove the phase reversal every line. Everything else is the same for PAL-M vs NTSC. So the ADVC should be set to NTSC and 7.5 IRE setup. After capture everything will be 480i DV YCbCr format.

edDV, so you mean I'd get the equivalent of 480 lines and not 330 ?
Thanks and sorry for the confusion,

Zetti

[edDV]

edDV, so you mean I'd get the equivalent of 480 lines and not 330 ?
Thanks and sorry for the confusion,

Zetti

No, sorry, the TV station never broadcast more than 330 lines. By lines here we mean "horizontal lines of resolution" as read from a chart. The number of pixels will always be 720x480 or 352x480 after capture.
see: http://home.aol.com/ajaynejr/vidres.htm



So, it appears you need to test the Samsung VCR to ADVC vs. the ATI AIW.

See if there is a big difference.

I have a ATI AIW and a ADVC-100 here.

I use the ADVC-100 to capture directly off a high definition cable box. I use this to make SD captures from HDTV (letterboxed over S-Video) and direct SD channel capture to DV format.

The ADVC-100 gets better quality than the AIW when attached to S-Video or composite NTSC inputs from the cable box. I use it mostly for "special" recordings. I also use the ADVC's DV stream to feed realtime software MPeg encoders like the ULead Video Studio 9.

The AIW tuner does OK with direct analog channels. I mostly use it to capture directly to MPeg2 for routine recording.

[edDV]

Lines of Horizontal and Vertical Resolution (maximum)*

VHS NTSC 240x336
VHS PAL 240x400
NTSC-M, PAL-M 330x336
PAL-B, PAL-G 400x400
DV (NTSC) 540x336
DV (PAL) 540x400



ref: http://home.aol.com/ajaynejr/vidres.htm
ref: http://icecube.wisc.edu/~dima/stuff/comp/vstandards.html

*as perceived on a resolution chart. Kell factor limits interlace vertical resolution to 70% of actual lines.

Rules of thumb to get to equivalent pixels

Horizontal: multiply by 1.25
Vertical: multiply by 1.4

[Zetti]

Hi edDV and everybody,

Thanks always, so, as far as I understood, the VCR's TV tuner -> Canopus ADVC-100 set is capable of taking full advantage of getting the "equivalent" # of 330 horizontal lines (4.2 MHz of bandwidth), OK ?

I'll take a careful look at the links you sent, very interesting;

A final question please, I promise: would a TBC-1000 (datavideo) instaled between the VCR and the Canopus ADVC-100 help, be harmful or neutral when it comes to TV broadcasts ?

For VHS capturing I always use it, but I'm afraid I'd better unhook it and link directly the VCR to the Canopus when getting TV broadcasts...or doesn't it make no diference at all ?

Thanks again, always,

Zetti

[edDV]

Hi edDV and everybody,

Thanks always, so, as far as I understood, the VCR's TV tuner -> Canopus ADVC-100 set is capable of taking full advantage of getting the "equivalent" # of 330 horizontal lines (4.2 MHz of bandwidth), OK ?

I'll take a careful look at the links you sent, very interesting;

Yes, if you assume the tuner operates perfectly, it will produce viewable resolution of about 330 "lines of horizontal resolution". That is the best possible from 4.2 MHz luminance bandwidth with a perfect transmitter and perfect tuner. "lines of horizontal resolution" means the point where the eye can no longer resolve alternating black and white lines on the screen. It is the point where it all blurs out. In the real world, the lines will blur at less than 330 lines.

"Lines of horizontal resolution" is not the same as sampled pixels. Digital sampling theory says you need to sample an analog source at least twice the maximum analog frequency contained in that signal to avoid alias products. Two times 4.2 MHz. is 8.4MHz. 8.4MHz minimal sampling would produce 448 pixels x 480 lines (576 lines for 50Hz systems).

All current capture cards sample at 13.5MHz or multiples of 13.5 MHz to produce a 704x480 (or 720x480) digital video frame. So, requirements are more than met for adequate sampling.

Next issue is how much can you filter down that 704x480 frame before you start seeing the test chart blur below the 330 mark (400 for PAL-B/G). Testing showed that happens around 352x480/576 for both NTSC and PAL for real world systems. For this reason 352x480/576 MPeg2 encoding is considered at least adequate for captured broadcast material. Best to try 352 and 704 on your equipment and make your own decision.

Your Canopus ADVC-100 captures to a 720x480 DV stream with 4:1:1 sampling. Both luminance and chrominance are oversampled in that case. Chroma (U and V) is broadcast with around 500-750 KHz analog bandwidth. 4:1:1 oversamples chroma at 3.375 MHz.

Your ATI-AIW also captures a 720x480 frame with 4:2:2 sampling (uncompressed), but can realtime encode that to 720, 704 or 352 x480 MPeg2.

A final question please, I promise: would a TBC-1000 (datavideo) instaled between the VCR and the Canopus ADVC-100 help, be harmful or neutral when it comes to TV broadcasts ?

For VHS capturing I always use it, but I'm afraid I'd better unhook it and link directly the VCR to the Canopus when getting TV broadcasts...or doesn't it make no diference at all ?

Television is broadcast with extreme timebase stability. There is no need for a TBC in the path unless it is for the Proc Amp (brightness, contrast, saturation, hue) controls. There will be loss since the TBC adds another A/D and D/A generation loss unless it has a bypass switch.

[Zetti]

Thanks a lot edDV,

I'll read and re-read carefully all the excelent technical information you supplied;

Thanks again,

Zetti