I have been wondering for awhile - is 720x480 DVD source conversion to 720x540 upscaling already? I have tried to upscale some DVDs of mine into 720x540 and the quality is okay for me. But I've been encountering lots of videos in 4:3 aspect ratio to 640x480. What would be the best resolution?
Also, is it possible that the resolution be 720x480 but the aspect ratio would be 4:3? I have been noticing some 16:9 ratio that have 720x480 resolution, but I don't know how they did that. When the video is played, the view will still be 16:9. To think it's 10bit h264 + AAC encoding. Been wondering how they did that.
I know how to use avisynth + meGUI, by the way.
Hoping for a positive response. Thanks!
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Is it up-scaling ? No. It is resizing
ALL dvds have a Storage Aspect Ratio (SAR) of 720*480 for NTSC (720*576 for PAL)
When the Display Aspect Ratio (DAR) is 4:3, the display is resized to 720*540. Both NTSC and PAL
When the DAR is 16:9, the display is 854*480 for NTSC and 1024*576 for PAL.
The variances are due to the simple fact that DVD pixels are not stored as square((PAR=Pixel Aspect Ratio) whereas they are displayed square.
h264 has nothing to do with the original dvd. You must be looking at a conversion.
All NTSC DVDs are 720x480 (well 704x480 is possible for 4:3, but pretty rare). The 720x480 resolution is either stretched to 16:9 or 4:3 on playback. DVDs don't use "square pixels". When you resize to 720x540 or 640x480, you're resizing to square pixels dimensions.
If you keep the 720 width the same and stretch the 480 height until it's 4:3, in square pixels terms you end up with 720x540. If you keep the original height and reduce the width instead, you get 640x480. Or you can resize to an in-between 4:3 dimension if you like. ie 704x528. There's no rule....
Mostly for 4:3 NTSC you can resize "down" to 640x480 without any noticeable loss of picture detail.
Alternatively, if you enable anamorphic encoding in MeGUI's script creator, you can encode the video using the original 720x480 resolution (resizing can be left disabled). The correct 4:3 aspect ratio will be set when encoding, and the encoded video will be resized to 4:3 (or 16:9) on playback just as it would if you were playing the original DVD.
The only downside to anamorphic encoding is not all hardware players support aspect ratios in MKV/MP4 files and will display the video as though it uses square pixels (so it'll look stretched or squished). PC software players will display it correctly. There's a media player in a TV in this house that doesn't display anamorphic video correctly so to avoid the hassle of having to worry about it, I resize everything to square pixel dimensions myself.
Sorry, you are both off to some degree.
As per the spec, NTSC DVDs can be any one of the following:
1. 720x480 with 16:9 DAR. Shows as ~853x480 when using square pixels in Windowed mode (not full-screen).
2. 704x480, with same features as #1
3. 720x480, with 4:3 DAR. Shows as 640x480 when using square pixels in Windowed mode (not full-screen).
4. 704x480, with same features as #3
5. 352x480, with 4:3 DAR. Shows also as 640x480 when using square pixels in Windowed mode.
6. 352x240, with 4:3 DAR. Shows as 360x240 or 640x480 when using square pixels in Windowed mode, depending upon the program.
ALL of the above will show at the resolution of the screen - within the constraints of the intended DAR - when shown in full-screen. Does not matter what the screen resolution is: 640x480 -> 4096x2160, or whatever.
Whether any particular dvd authoring app can allow all those resolution options is just a matter of their programmers' thoroughness or lack thereof.
Whether to resize or not should ultimately be decided on the target: can the app(s) that are going to be using this footage DEAL with non-square pixels?
If they can, you shouldn't be resizing, plain & simple. Leave it as it was encoded on the DVD in Non-square pixels (as are ALL DVD resolutions). This will help retain as much of the original quality as possible (barring re-compression losses).
If they can't, resize to non-square pixels. The best sizes to use are the ones I mentioned above that show up in Windowed mode for each rez choice.
It destroys the interlacing smoothness (actually blurs it out, and often doesn't even do that correctly for interlaced material). When resizing either NTSC or PAL to square pixel dimensions, resize ONLY the horizontal dimension (whether larger or smaller), NEVER the vertical. This goes back to how things are sampled from analog to digital (horizontal points along a scanline are guessed at anyway, but the lines themselves are discreet).
Personally, once you understand fully how AR works, it is inconsequential to work with them correctly. I never resize to square pixels, except when the target requires it.
Thanks for the responses! I understood more or less.
So 640x480 then
Thanks guys again for being brilliant
I would always bow to your knowledge but....
853 is an odd number !!!!!!
853 is an exact conversion (actually 853.33333333etc) and doesn't take into account mod4, mod8 or mod16 requirements, so it would be somewhere around that figure. Between 850-856 are common. That's why I put the "~".
Keeping in mind I always crop, which invariably results in the height being resized to some degree, I'll confess if de-interlacing and resizing this 4:3 PAL DVD to 640x480 has cost me much, aside from a 30% file size reduction (compared to not resizing the height), I'm having a hard time seeing it. Even if it could be argued the encode where the height wasn't resized looks better than the encode where it was, running fullscreen on my TV the latter still looks better than the original 720x576 video to me.
"Original" vs "Non-resized Height" (after cropping) vs "Resized Height" (after cropping).
crop(14, 4, -14, -4)
Spline36Resize(758,568) # or Spline36Resize(640,480)
I'll confess I rarely resize the height "up" unless it's just by a little bit to achieve a certain resolution. For 4:3 PAL I sometimes use "in-between" resizing such as 704x528 or 720x540, but I'd agree for NTSC there's probably no point.
I understand the logic behind not resizing the height. In a perfect world you wouldn't and often I'll try not to, especially when re-encoding 16:9 DVDs containing widescreen video, because they tend not to be interlaced and it's just a matter of cropping and stretching the width to the correct aspect ratio, then encoding. The final dimensions aren't critical to me when it comes to wider than 16:9 aspect ratios.
If you crop when encoding (I know you don't crop yourself but I couldn't encode without it) and you prefer to output nice 4:3 or 16:9 aspect ratios where applicable (as I do), there's invariably going to be a little resizing involved. Often I'll crop a few pixels and resize 16:9 PAL to 960x540, or NTSC to 832x468 (because they're both exactly 16:9), but given the video is usually upscaled to 1080p on playback anyway..... to be honest a little height resizing before encoding generally seems to be neither here nor there.
In fact... for PAL 16:9, Spline36Resize(1024,576) or Spline36Resize(960,540) tends to have a slight sharpening effect compared to anamorphic encoding or even the original video.... which I generally don't mind given DVD video doesn't tend to be overly sharp.
Last edited by hello_hello; 18th Jun 2014 at 16:44.