Reason to resize SD video to 720x540 ?

[Dickieg10]

Hello all, newbie here.

Mostly with VHS and minidv captured video.
In researching, I am seeing that some are using ffmpeg to crop and resize the footage to 720x540.

What are the benefits in resizing to this versus leaving as 720x480?

My videos were captured this method & format:
VCR to minidv cam pasthrough to pc by firewire
720x480 at 29.970fps, DV (NTSC)

Thanks in advanced.

[jagabo]

An NTSC DV cap has a frame size of 720x480. If you downscale to 640x480 you lose some resolution horizontally. If you upscale to 720x540 you don't lose any resolution horizontally but you must deinterlace before scaling. And the picture might be a little blurry vertically. Both are 4:3 frame sizes, suitable for square pixel encoding.

[manono]

...versus leaving as 640x480?

Are you saying they're already 640x480? They weren't capped at 720x480?

[DB83]

But surely 720*540 is 'illegal'. Yes it is 4:3 and, yes, it will in all probability play fine in a PC but other playback devices ?


Surely the 'resize' should be 720*544

[jagabo]

But surely 720*540 is 'illegal'. Yes it is 4:3 and, yes, it will in all probability play fine in a PC but other playback devices ?

Almost everything supports mod4. Most devices even support mod2.

[Dickieg10]

My videos are capture at 720x480, I corrected my original post & added some more details.

I do plan to deinterlace with QTGMC using avisynth & ffmpeg.
My commands would deinterlace, crop, resize (if needed) & convert to a different container in same pass.
Will probably use a prores codec.

Right now, I have people people who want this footage. Some on DVD, others on a streaming platform.

Just trying to understand what size would be best for long term storage.

[hello_hello]

An astounding amount of iTunes AVC video is mod4. I've even seen mod2 heights on occasion. Players don't care any more.

Dickieg10,
The only DVD format for which you need to reduce the width or resize the height, assuming you resizing to square pixel dimensions, happens to be 4:3 NTSC.
16:9 NTSC and PAL can be resized to square pixel dimensions by increasing the width. ie before cropping:

16:9 NTSC - 854x480
16:9 PAL - 1024x576
4:3 PAL - 768x576 or 786x576, depending on how you resize.

Not all players display anamorphic video correctly (my TV's media player doesn't), so I resize everything to square pixels, but if you keep the original resolution, or don't resize after cropping, and set the appropriate aspect ratio when encoding, you're not increasing the amount of video that needs to be encoded.

[jagabo]

Just trying to understand what size would be best for long term storage.

The original DV AVI.

[DB83]

But surely 720*540 is 'illegal'. Yes it is 4:3 and, yes, it will in all probability play fine in a PC but other playback devices ?

Almost everything supports mod4. Most devices even support mod2.

Ok. But I now read the addit info in the OP that the capture is 4:3 DV-AVI. Surely that displays at 640*480 and would be the more appropriate resize ?


Now if these captures were PAL I am sure that one would not recc a resize to 720*540 >> claimed loss of definition on the vertical << but resize to 768*576. You would not gain definition by increasing pixels from 720 would you ?

[jagabo]

Ok. But I now read the addit info in the OP that the capture is 4:3 DV-AVI. Surely that displays at 640*480 and would be the more appropriate resize ?

Only if you display it at that size. The player will directly scale from the source frame size to the final output size. So if you're watching on a 1920x1080 display it will display as 1920x1080 (for 16:9 DAR) or 1440x1080 (for 4:3 DAR). There's no need to reduce the resolution to 640x480 first.

Now if these captures were PAL I am sure that one would not recc a resize to 720*540 >> claimed loss of definition on the vertical << but resize to 768*576. You would not gain definition by increasing pixels from 720 would you ?

You will not gain definition by the upscaling to 768. But you will avoid losing resolution by downscaling the vertical to 540.

Note that every scaling can potentially damage the video So the fewer scaling steps the better. I usually keep the original resolution and encode with sample aspect ratio flags. Then only use devices that display that properly. But, as has been stated, some devices do not obey the AR flags -- so that's not for everybody.

[hello_hello]

Ok. But I now read the addit info in the OP that the capture is 4:3 DV-AVI. Surely that displays at 640*480 and would be the more appropriate resize

Every 4:3 DVD I've met has an ITU or mpeg4 aspect ratio, making it 15:11 rather than 4:3, so without cropping 8 pixels each side, something like 656x480 would be more accurate. I think the same applies to DV. That aside, I tend to go with the "1080i has the same spacial resolution as 720p" theory for interlaced sources. You can generally de-interlace 1080i to 50 fps or 59.94 fps and downscale to 720p without sacrificing much visible detail, if any, so the same principle gives you a bit of wiggle room for interlaced DVDs. I always crop to 4:3 and aim for the next mod4 dimensions down for NTSC, which is 624x468.
You can do a similar same thing when encoding anamorphically, but if you want the same output dimensions each time you have to crop each episode the same way or prepare for some resizing anyway. My OCD is aggravated more when the dimensions are different.

Now if these captures were PAL I am sure that one would not recc a resize to 720*540 >> claimed loss of definition on the vertical << but resize to 768*576. You would not gain definition by increasing pixels from 720 would you ?

For interlaced 4:3 PAL I usually, de-interlace, crop, and resize to 640x480.

A PAL DVD running full screen.

[Attachment 55723 - Click to enlarge]

A 640x480 encode running full screen.
The minor loss of fine detail is solely due to denoising/deblocking.
Whatever was lost was gone before I resized.

[Attachment 55724 - Click to enlarge]

Edit: Fixed posting the same pic twice.

Is DV interlaced? I can't remember. If not I'd probably be less enthusiastic with the downscaling.

[azmoth]

I once had a hybrid NTSC dvd( telecined and interlaced), and for the life of me could not get it right. An IVTC in Fairuse Wizard still left severe combing and not the desired resolution and even resorting to an Xvid in the great AutoGK left a horrible green line at the bottom of the 4:3 video, despite 704x528 exact 4:3 resolution. In the end encoded it in Handbrake and the only resolution it allowed me to get an exact 4:3 was 720x544 after much testing out short samples with telecining and decomb set to auto as well. The anamorphic strict settings etc always ended up as 1:5 ratio on a 720x480 cropped. It would not allow me 704x528 which I wanted originally. 720x540 is definitely not correct I think.

720x544 or 1:32 sufficed!

[jagabo]

Here's a 720x480, 29.97 fps, Lagarith AVI file. See if you can resize to 640x480 or 704x540 or similar ~4:3 frame size and see how it looks. Then watch that video full screen on your HD monitor. Compare it to the original video viewed full screen.

[manono]

Right now, I have people people who want this footage. Some on DVD, others on a streaming platform.

For DVD, of course, you leave it alone. If for streaming - YouTube for example - anything at 540p will just be downscaled to 480p when reencoded by YouTube. I don't know about other streaming platforms. So, after cropping away the black, 640x480 it is.

[hello_hello]

Here's a 720x480, 29.97 fps, Lagarith AVI file. See if you can resize to 640x480 or 704x540 or similar ~4:3 frame size and see how it looks. Then watch that video full screen on your HD monitor. Compare it to the original video viewed full screen.

Obviously that won't look the same, but I've never seen a DVD like that in the real world.

Do you have an interlaced version? De-interlacing made far more of a mess than simply resizing it did.

That's not really a fair test because you can't even upscale it directly to 1440x1080 without changing it. The only way to do that is to upscale using the storage aspect ratio, not the display aspect ratio.

[ItaloFan]

Every 4:3 DVD I've met has an ITU or mpeg4 aspect ratio, making it 15:11 rather than 4:3, so without cropping 8 pixels each side, something like 656x480 would be more accurate. I think the same applies to DV.

Getting off topic here, but based on what I have seen with my late-model HandyCam, I think what happens is Digital8 DV recordings you make with the camera are, by design, full-frame 720x480 4:3. But if you play a Video8 or Hi8 tape, or you use the AV input like the OP is doing, then the analog source material is captured BT.601-style, so the DV result is 720x480 15:11—i.e. it has 8px black bars along the left and right sides, and is slightly squished.

However, the software reading the DV signal coming in from the camera (e.g. Sony PlayMemories Home) has no way of knowing what the source is, so it just blindly puts a 4:3 tag in the AVI (actually AVIX) files that it writes. One could use FFmpeg to retag the non-Digital8 material as 15:11, or when transcoding, crop 16px and tag the resulting 704x480 as 4:3.

Is DV interlaced?

Usually.

[jagabo]

Here's a 720x480, 29.97 fps, Lagarith AVI file. See if you can resize to 640x480 or 704x540 or similar ~4:3 frame size and see how it looks. Then watch that video full screen on your HD monitor. Compare it to the original video viewed full screen.

Obviously that won't look the same, but I've never seen a DVD like that in the real world.

But you often see parts of the picture that look something like that. Stripes on somebody's shirt, windows in a skyscraper in the background, etc.

Do you have an interlaced version? De-interlacing made far more of a mess than simply resizing it did.

That video is interlaced if you say it's interlaced, progressive if you say it's progressive. If you treat it as interlaced the area with the horizontal lines should flicker to all black for 1/60 second, all white for 1/60 second, etc. -- because one field is all black and the other all white.

That's not really a fair test because you can't even upscale it directly to 1440x1080 without changing it.

You can't upscale anything without "changing it". Depending on what scaling algorithm you use, and the size of the final output, you will see more or less moire artifacting. What you can do is scale only once, during playback, rather than scaling to some intermediate size, encoding, then scaling again during playback.