640 x 480 vs. 720 x 480: The Confusion That Keeps On Giving

[Avagadro1]

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[davexnet]

Was the original capture 640x480? If so, PE set the project setting to match.
When the file is rendered in PE aren't you able to choose a DVD template ?

The NTSC DVD standard is 720x480, the authoring programs (those that package the source assets, mpeg-2, audio, subtitles,
into the Video_ts folder) will not accept 640x480 as input.

[dellsam34]

It's neither one, The proper resolution for a video capture is to crop off the 16 horizontal black pixels added by the capture card during capturing then set the pixel aspect ratio to 10/11 for NTSC and 12/11 for PAL/SECAM for a perfect 4:3 frame during encoding to the final playback format, With this you don't need to resize, here is a sample captured from VHS and encoded that way to see if it's compatible with your playback options, if it is then there is no need to resize to a square pixel format, you loose a lot of resolution.

By the way 704x480 is an official resolution of DVD 4:3 (full screen), 720x480 is anamorphic widescreen not for analog sources such as VHS.

If you insist on using DVD the proper way of doing it is to capture lossless AVI first, crop to 704x480 then encode to MPEG-2 using the SAR parameters above, from there you can author to DVD, Capturing to mp4 then to mpeg-2 with a resized resolution is a disaster.

[manono]

I just read that 640x480 is not a “legal” format for DVD. (I’m not sure what “legal” means for other than commercial producers of DVDs.)

It means it'll be impossible to author a DVD at 640x480.

...so I seem to be stuck with 640x480.

It could be resized yet again to 720x480 and then you could make a DVD of it. But that means unnecessary degradation of the video on the way to the DVD.

Will my PE project, after initially saved to a disc-burnable format, display properly on both a computer monitor and a TV?

It won't display at all as you'll never be able to make a DVD directly from a 640x480 video. Now, I'm assuming you want to make a real DVD. You could burn the 640x480 MP4 as a data disc and some players might play it, but it won't be a DVD, which is what I think you want.

Can someone explain why this captured-and-converted video turned out to be 640x480 rather than 720x480?

You screwed up something in your editing program. I don't use it so maybe someone else can be more specific.

Would that work, i.e., without distorting the video image?

You want a 'distorted' image. Then you encode for MPEG-2 DVD with the DAR set for 4:3 and it'll play 'undistorted' when you're all done. You want to keep it 720x480 all the way through to the end. Unless you crop the black bars and get it down to 704x480. That's okay as well, and probably better.

[Cornucopia]

I am concerned that the OP started off on the wrong foot from the beginning, with the "chinese made analog to digital converter, to mp4".

As mentioned,best practices for vhs: 720x480 (or 704, depending on card & drivers) -> uncompressed/lossless temp format to edit. Edit project using same rez as source. Export to uncompressed/lossless master. Also export as mpeg2 for dvd, BOTH using same rez. Mpeg2 should have option to set AR in codec (either 4:3 or 16:9 as befits the source).

640x480 shouldn't ever enter into the workflow until you decide to have a streamable/portable/shareable/youtube-friendly avc in mp4 as an optional additional export. Then, the shrinking of the horizontal will be baked into the square-pixelled file. And only ONCE.


Scott

[Avagadro1]

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[Avagadro1]

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[Cornucopia]

It's actually pretty simple.

All vhs is analog. Analog NTSC (which is what you have been and would be dealing with here in the US) is ALWAYS ### X 525. The # is variable because it's analog, but due to its limited bandwidth (6MHz) is not truly infinite. But it IS continuous along the scanline, which means that any sample rate used will be as accurate as that rate allows. The 525 is discrete, because there is clearly only that amount of scanlines, as per the spec timing.

The 525 includes not just visible picture, but also blanking/vertical interval/timecode/closedcaptioning, etc. So to get solely the visible picture scanlines, sampling/digitizing would capture 486 lines. That's what the pro capture cards do. Consumer ones expect to make use of certain compression shortcuts, and one of those requires that the # of lines be evenly divisible by 4. 486 is not, so they compromised by dropping it to 480 (mainly by cutting off the top where those extraordinary line types live). Ta Da!

The # of horizontal pixels per scanline depends on the sample rate. Very, very old school capture cards (c. mid-late 80s) did sometimes capture 640, but their samplerate was odd.
The powers that be came to an international common set of sample rates such that both NTSC and PAL and SECAM could be digitized by the same card & they would have similar # pixels per scanline. The agreement document was CCIR (aka ITU) 601. That set the analog sampling to capture 704 pixels (ntsc) or 702 pixels (pal), usually contained in a 720 pixel frame (so leftmost 8 and rightmost 8 are black), per each line.
Again, the vhs doesn't have pixels (which are digital sample points) because it's analog. But when it gets captured to digital, ntsc should almost always be captured at 704x480 (within 720x480 frame, or not) or 720x480 (ever so slighty stretching the picture), depending on how closely the capture card/device is in compliance with ITU-601. Yes, these all use rectangular pixels.

No 640x480 there. To get that, these knock-off, non-compliant cards are squeezing (aka rescaling down) the image to fit a 640x480 frame. Just because it thinks that's what some/most consumers might want. But it DOES lose quality in the conversion, not even counting lossy compression.

Mp4 will accept 640 or 704 or 720 (x 480) so no surprise. But like I said, you were Already at a disadvantage prior to ever even getting into your editor.

Yes, you were able to export to 640 x 480, and the dvd software was able to "accept" that as a source. But to make a true DVD, it could not keep it like that and it had to recompress and resize it yet again (likely to 720x480, as that is the most common dvd framesize). So that is at least 2 or 3 lossy encodes, and at least 2 resizes to make it to the dvd. As I mentioned, best practices would guide you so that you only have 1 lossy encode and NO resizes. Should be a noticeable difference in perceiveable quality (but there is always variability with bitrates, and with user sensitivity).



Scott

[manono]

However, I read a few weeks ago that now-a-days, for my purposes, I should instead capture to MP-4.

You should capture to lossless AVI.

Thus I assume, but don’t know for sure, that 640x480 was how the old VHS camera recorded the video.

Can't you just look at your captured MP4 and figure out the resolution? I'm fairly certain your VHS camera didn't capture as 640x480.

...that at 640x480 I would not be able to create a menu or burn to DVD.

You can't, although I mentioned it could be resized back to 720x480.

...what you commonly call “authoring”

Authoring is taking DVD-compliant assets (video, audio, subs, maybe, chapters, maybe) and creating the IFOs, BUPs, and VOBs that make up a DVD.

1) Despite the video being 640x480, there was no problem adding a DVD Menu or burning to disc.

Then either it wasn't 640x480 to begin with or it was resized to 720x480. You can easily determine your DVD video isn't 640x480. Here, read "What is DVD?" on this site

[Avagadro1]

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[davexnet]

640x480 or 720x480, it's usually a setting in the capture software

The VHS tape is analog, it doesn't have a digital resolution. The 480 corresponds to the NTSC scan lines of 525
(after cropping), while the 720 is the sampling of each line (far beyond any detail that VHS was capable of)
and of course, it matches the DVD requirements

[Avagadro1]

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[davexnet]

davexnet,

You are implying (absolutley ok, I understand you) that in my initial/practice captures (using PotPlayer, not VirtualDub), I somehow or another INADVERTENTLY had the software set to capture at 640x480. Is that your thought?

If so, I infer that you suggest that I review my PotPlayer settings (just for purposes of edification, not recapture), to see if, in fact, there was a setting for capture resolution, and it was set for 640x480.

Is that your suggestion?

Thanks very much.

I can't attest to whether Potplayer offers this or not -you'll have to look, but certainly, IuVCR/IuVCS and Virtualdub can capture at 720x480,
probably also AmarecTV, since this a common capture format

[Avagadro1]

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[davexnet]

and burned to DVD nicely.

This just means the DVD software resized it when creating the DVD; 640x480 is not a valid DVD resolution

[zing269]

HOWEVER, what the drop-down box is reading is its default (I did not earlier know about it or touch it), which is the word “ORIGINAL”.

What should we make of this?

All that means is that your capture device was set to output at 640x480. You will need to figure out how to set the output resolution in the capture device.

[Avagadro1]

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[manono]

Is that what you are suggesting?

Sort of, although I believe he and most of the rest of us would do the cropping and other filtering in AviSynth and then open the script in VDub to be saved as a lossless AVI.

I will have to select a (final) resolution format, which (of course?) in this case would be 720x480.

No, the final resolution for your DVD should be 704x480.

[dellsam34]

Yes, vdub allows you to remove the padded 16 pixels from the video that were added by the capture card for safe measures , You can customize your crop individually on each side as long as the total pixels removed is 16, Not sure if it can be done during capturing but the good thing is this process is quick and completely lossless. 704x480 is a legal resolution and recognized by most if not all video codecs. If you don't mind having black bars and rough noisy edges on the frame you don't have to do this, however the aspect ratio will be off by 16 pixels if you leave the side borders but most people would not notice a squeeze of 16 pixels of the active video area.

[Avagadro1]

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[Avagadro1]

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[jagabo]

The advice about not cropping is for when you must resize after cropping. For example, many people want to remove head switching at the bottom of the frame (VHS caps) -- say, 8 lines, for example. If you crop it away you must resize (or add back borders) for DVD because 720x472 is not a legal size for DVD. In your case you are cropping black borders at the left/right of the frame leaving 704x480. That is a legal size for DVD so you don't have to resize or add back borders. And that 704x480 conforms to both the ITU spec (approximately) and the MPEG2/DVD spec for aspect ratios.

[Avagadro1]

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[jagabo]

One reason for capturing 720x480 is so that you can crop the black borders accurately -- they're not always even on both sides. But if you can capture accurately at 704x480 you might well do so.

[Avagadro1]

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