anamorphic vertical stretch makes no sense...

[fibbingbear]

I've been learning a lot on these forums about anamorphic video. I tried a simple experiment: captured some NTSC 720x480 footage off of my card (original DAR was 4:3), encoded an mp4 with the DAR in there, and opened the file. To my surprise, on playback the file stretched vertically to match the DAR.

Is this normal? I was under the impression that the whole point of anamorphic was not to stretch/shrink vertically unless it was absolutely necessary.

In fact, at http://www.animemusicvideos.org/guides/avtechbeta/aspectratios.html , they state:

Full screen NTSC dvd footage is usually 720x480
and
NTSC dvds need resizing to 640x480 to be 4:3
along with
You may notice that NTSC is downsized and PAL is upsized - this is purely and simply to keep the vertical resolution the same in case someone uses these values on an interlaced source

So why would a video player use the DAR to change the vertical resolution? This isn't making sense to me.

Here are some images to demonstrate what I mean:

Original capture image (720x480, without DAR set):
http://ybit.org/fb/ati1.jpg

Here's what I think it should look like on playback (656x420 with DAR of 1.36):
http://ybit.org/fb/ati2.jpg

Here's what it actually looks like on playback (720x528 with DAR of 1.36):
http://ybit.org/fb/ati3.jpg

Sorry, these images were not captured from VLC since it does not take DAR into account when capturing images (and printscreen doesn't work with VLC), but I resized the image to match what VLC looks like when it plays.

[J_Darnley]

Well you can scale a video to what ever is necessary to achieve the correct aspect ratio. Does it matter whether it is scaled up or down if you view it in a window? If you prefer that VLC resize in a different direction, resize the window yourself. Perhaps the behavior of VLC is to upscale so that no details are hidden. Actually, that sounds quite sensible.

The point of anamorphic encoding to preserve maximum vertical resolution because apparently the eye/brain is more sensitive to vertical sharpness than horizontal.

[Mug Funky]

so long as the playback software knows what it's doing, it doesn't matter how it scales it.

vertically scaling an interlaced picture will only create "shimmering bars" if the software is not interlace aware. if it is aware of the picture structure it can deinterlace to 2 frames, then resize each on playback.

obviously it's better to upsize than downsize for display purposes. of course, some software achieves the deinterlacing and resizing better than others.