VHS-C camera resolution?

[Nelson37]

I have a JVC GR-AXM100U VHS-C camera. All the manual says about capture resolution is "NTSC Standard". When connecting camera directly to ATI AIW 128 pro, VDUB says video is 720x480. Is this possible? I thought 352x480 was best from VHS-C.

[mbellot]

Its an analog signal, so theoretically you can get infinite data, but the reality is much lower.

Your ATI card may be able to capture the signal @ 720 x 480, but you are probably just getting more bits, not more info.

It really depends on what your "end use" is anyway. If you are converting the tapes to DVD then it makes sense to capture at DVD resolution (get maximum data at capture rather than interpolate later).

If VCD is your target then you can probably afford to capture at 352 x 240 using a low loss codec (Huffy is supposed to be pretty good) and just re-encode to Mpeg1/2 for your VCD.

If your final target is PC video (i.e. AVI) then you need to keep your target audience in mind when selecting video size and codec. Some of the old DivX codec (4.x) AVIs I have made look fine on my 1GHz Celeron at 720x480 (DV Camera source), but are totally unwatchable on my 266Mhz PII Dell laptop.

[big_hed]

The VHS standard is 240 lines of vertical resolution. Capturing at 720x480 will capture all the detail, and a lot of VHS noise. Like mbellot said, if you are burning to DVDR, then capture at 720x480 and save the encoding time. I have the AIW Rage Pro, and capture VHS at 720x480 straight into MPEG2 with no frame loss.

[Anonymous65]

352x480 is a perfect capture resolution for VHS video tape, and it can be done in real-time with a bit rate of 4Mb/sec. You will get over 2 hours per DVD-R. A T-120 VHS tape = 4.7GB DVD-R disk, the best way of backing up a VHS video tape.

[Nelson37]

Let me try again. Is it POSSIBLE that this camera will output 720x480 either to internal tape or on DIRECT FEED to PC? Can these be different?

OR, is there a program which will tell me what the resolution is for the incoming stream? I thought Vdub gave this info, but since it says video stream is 720x480 I'm not so sure.

I am not looking for advice on encode or capture, I just want to know what I have to work with. Although thanks for that advice, don't want to sound ungrateful.

[mpb]

Let us try again.

ANALOG video has no pixel resolution. It's limited only by how clear the source is. However in terms of useful chunks of image, it is generally accepted that VHS and VHS-C tapes output video that is best interpreted as approximately 352x240 if it were digital video.

Capturing that ANALOG signal at 720x480 will grab every little possible bit of image that tape is feeding you... and a hell of a lot of crap at the same time, useless bits, pixels being wasted because there's no material image information interpreted for them by your capture software. Coming from a VHS source, a 352x240 capture is going to look more like its original source than a 720x480 source.

To give similar examples, ANALOG video is present on SVHS, Beta, and laserdisc as well. SVHS is considered to be about 352x400 comparatively, thinking of each pixel as a rectangle and not a square. Laserdiscs interpret as an approximate digital resolution of, what, 512x384 as I recall (corrections anyone?). I typically capture them at 640x480 or higher, since the image fidelity is so high. VHS tape, not nearly as high.

[Nelson37]

Thanks, I think. Now I am REALLY confused. So you are saying that analog video does not have an actual resolution, only an approximation?

1. Is there an "NTSC Standard" resolution other than 720x480?

2. Would it be likely that the approximate resolution would be better recording direct to hard drive rather than tape? Or just better quality that would make a higher resolution more feasable?

3. Is there any type of viewer which would correctly indicate the appropriate (or correct) resolution for a given clip, or is this not possible to determine?

Sorry to be so anal, but the primary purpose for my VHS-C camera is to record videos of my kids, which are precious to me beyond my ability to describe.

[Anonymous65]

1> D1 video, a standard used by broadcast stations, and also used by digital VCR's used for broadcast is set at 720x480. Also, DVD is also 720x480 pixels. This pixel resolution is technically higher than the NTSC TV standard that specify video resolution up to 4.5MHz. Over the air NTSC video with a bandwith of 4.5MHz is fairly equal to 640x480 pixels. So, capping cable or over the air video over 640x480 is a waste of data.

2> Don't understand the question. It doesn't matter where you record the video to as far as digital, if analog, you are limited by the system you use, VHS, S-VHS, Beta, U-mat, Betamax, D2, 1", DVC-Pro and so on.

3> To find the resolution of a camcorder, shot a resolution test chart. When playing back the tape of the test chart, you can read how many 'lines" of resolution you have. By using a formula, you can find the aproximate pixel resolution.

[Anonymous65]

For more info on a test chart, and to download one you can print, go to http://steve.kittelsen.com/video/digital.htm

[sudsbrewer]

Actually, the number of lines is fixed 240 lines/field x 2 fields/frame = 480. The horizontal TV/VHS signal is an analog signal. It is a constantly variable wave that determines color and intensity as the beam sweeps across the face of the TV. This horizontal signal is sampled at 720, 352 or what have you. The number of horizontal samples is only important once it has been digitized for storage into a "standard" MPEG1/2 file that can be stored and played back as VCD/SVCD/DVD. It's the VCD/SVCD/DVD formats that determine what horizontal sampling is supported/required.

suds

[mpb]

For videos of your kids, naturally you'd want to preserve them at the best rate possible.

You're reading that correctly... analog video doesn't have a resolution in the sense that digital video does, but it contains a certain amount of information, and that information is transmitted with a frequency. The output of this can be interpreted as having a certain resolution with digital video. D1 video, right out of the tower, has an absolute ceiling of 704x480, which is one of the valid DVD resolutions. (notice that's not 720, it's 704. double the 352. But that's because of the shape of the pixels.) So when someone says laserdisc is 544x480, what they mean is that the analog information in that signal can be sufficiently contained in a digital video stream at a resolution of 544x480 or more.

VHS is much less, but there's still plenty of information there. Capturing at 352x240 is a good way to get a file that is very close in content to what's on that videotape. However, there's a little bit of data lost that way, and in order to acquire as much information as absolutely possible, and to preserve the video of your kids for the future, you may find better results from a guide here on VCDHelp... except I can't find the one I'm referring to... anyone wanna help here? The gist of the guide was:

Capture to 640x480, well exceeding the VHS tape's signal capability.
(capture audio at 48khz PCM, not 44.1, for reasons I'll explain shortly.)
Deinterlace to a prog scan stream, so you're essentially 640x240 NI now.
Use TMPG to encode with slowest/HQ motion to MPEG-1 VCD, the video only.
Remux the video and the audio, and then add to DVD-R.

You get a valid stream for DVD (Mpeg 1 352x240x1150k) with all-important 48khz audio, and best of all this stream should LOOK AMAZING. This is a non-interlaced stream with maximally efficient compression per quality. The 640 horizontal is converted to 352, but by making the pixels horizontal and interpolating in the excess pixel space. This captures so much of the information present on the source tape, that it's effectively impossible to discern what's missing, and depending on how old or damaged your source tape is, there might not BE anything missing... what you see at 352 might be all of the discernible information present on the analog source.

This is a LITTLE different from what I'm doing with tapes right now. For simplicity's sake and without deinterlacing (so the result files are really only useful on a set-top player, not a computer), I am capping at 640x480 or higher, and then encoding with TMPG to 352x480 Mpeg-2. This is also a valid DVD resolution. For most source tapes, this is as clear as they can be captured. Best of all, this resolution (known as half-D1) requires half as many bits for an equivalently clear picture than full D1, due to the simple math of how the bitrate works. So at 4900k, this resolution is as clear as the best-encoded DVD, not counting the limitations of your source tape. If you are never concerned with playing these files on a computer, and perpetual set-top player operation is your goal, I'd suggest that. Older threads go into better detail.

[Nelson37]

Thanks, now I'm getting it, MPB that's pretty close to what I'm doing now, good to know I'm on the right track.

#2. I guess what I meant here was to ask if the tape rather than the camera was the limiting factor. I have bypassed the tape recording by plugging the video cable from the camera into my capture card and feeding the camera signal directly, capturing without recording to tape, it seemed a little better but difficult to be sure. (PC vs TV, etc)

Skittelsen thanks for res chart link. Am I correct that resolution is determined by the point where the converging lines can no longer be distinguished? Is there somewhere an explanation for what the rest of the figures and numbers are used for?

[mbellot]

Nelson,

If your goal is to capture vidoes of your kids then I have a real simple suggestion.

Buy a MiniDV camcorder.

After farting around with a Pinnacle PCTV card and *my* old VHS-C camcorder for months without any great happiness I went out and bought a Canon ZR40 miniDV camcorder.

I picked the ZR40 specifically because it has analog inputs (many lower priced units don't). I have several clips of my daughter from birth to one year that were all on VHS-C that I *never* watched for fear of ruining the tape forever. Now every moment is stored in digital format, safe from being worn out.

As a bonus, the miniDV camcorder "captures" the analog input at DVD quality resolution (720x480). Using the VHS-C camcorder as my source and going directly (18 inch cables) into the ZR40 has resulted in picture quality I could only dream of with the PCTV card.

Only downside to miniDV is the filesize, about 18GB per hour of video...

Its not the most economical solution, but it has made me very happy.

Best of luck whatever route you decide to take.

[vhelp]

Nelson77,

You should know by now that for good quality video capturing and
encodng, you need to ONLY capture 352x480 (not 352x240) and then
encode to SVCD. ie,
* capture at 352x480
* TMPG: load in the SVCD template
* set to Interlace, and in Advanced tab, set to Interlace
* you whicher Bitrate Rate control you want, ie, CBR/CQ/CQ_VBR/2pass
and set to some like, 2520!!
* set audio to whatever, min. of 128k
* just encode!!

No need to capture SO high, ie 720x480, and in the mean time, drop
so many frames. Just capture at 352x480, period! And, of course,
folow the simple guide above.

The only problem you might encounter w/ quality is your:
* tape quality
* tape speed you recorded in, ie SP or EP or LP, SP being the best
for quality
* how much you zoomed in and out
* shaked via your shaky hands
* light source ie, too low a light source will derail your quality,
ie even though the video may look fine on your TV, your encoder
will not process the low light levels very well or effectively.
* all the above applies to DV as well!! but with the exception
that DV give's you the ability to Transfer via firewire (NOT capture)
and will have a resolution of 720x480, NOT this DVD nonsense
that's floating around. Too many people pipe-dreaming DVD quality,
and this is just NOT so!! DV is not Hollywood!! I have a DV cam
Canon ZR-10, and have plenty of experience with it, and although I
can get great looking videos out of it, I can say it is NOT DVD
quality!! Plain and simple, AND truethfull!! But, quality WILL be
better than any VHS or VHS-C etc. camera, IF properly encoded!!
Its all in the encoding, NOT your camera, though you camera does
play a part in it.
* etc., etc.

* In the future, when you do use your VHS-C or (should you decide to
upgrade to a DV cam) make sure your video footage has plenty of
lights!!
* make sure you use the ZOOM feature sparingly!
* use a tripod instead of holding in your hand
* turn off "stabilizer" if mounting on a tripod (else adds noise)
* etc.

-vhelp