Resizing: Resolution and Aspect Ratio

[roflwaffle]

I'm trying to encode a 1280x528 video file using HCEnc. This is the AVISynth script I wrote:

DirectShowSource("video.mp4")
BilinearResize(720, 297)
Crop(0, 1, 0, 0)
AddBorders(0, 92, 0, 92)

It resizes, crops and adds borders to the video so that the output resolution is 720x480. However, is this how I should be doing it? I mean, what I never understood was the option to choose an aspect ratio in HCEnc. I have it set to 16:9. What does this mean exactly? 720x480 resolution means that the aspect ratio is 1.5:1, so how does the additional option to set the aspect ratio affect the output? Should the input resolution be 720x405 rather than 720x480?

[Baldrick]

Moving you to our conversion section.

[Case]

If your 1280x528 movie is square pixel, then
to get that in a D1 16:9 (like DVD) resolution frame,
resize to 720x(intermediate height),
where intermediate height = 480*(528/1280)*(16/9) = 352
and add ((480-352)/2=) 64 pixels on top and 64 pixels on the bottom.

Or think of it like this:
1280x720 is full frame 16:9 720p. 1280x528 takes 528/720 = 73.3% of the height.
720x480 is full frame 16:9 D1. 73.3% of 480 = 352.

[roflwaffle]

Thank you, Case.

[AlanHK]

I'm trying to encode a 1280x528 video file using HCEnc. This is the AVISynth script I wrote:

DirectShowSource("video.mp4")
BilinearResize(720, 297)
Crop(0, 1, 0, 0)
AddBorders(0, 92, 0, 92)

It resizes, crops and adds borders to the video so that the output resolution is 720x480. However, is this how I should be doing it? I mean, what I never understood was the option to choose an aspect ratio in HCEnc. I have it set to 16:9. What does this mean exactly? 720x480 resolution means that the aspect ratio is 1.5:1, so how does the additional option to set the aspect ratio affect the output? Should the input resolution be 720x405 rather than 720x480?

The resize and crop lines look a bit odd.
Generally you work in even numbers, make most software happier.

If you're trimming some crap off the frame, do the trim first and them resize the clean image.

Otherwise, the AR option in HCEnc sets a flag in the file. Software handling that file, and ultimately the DVD player, then treat it as 16:9 or 4:3, appropriately.
It makes no difference to the encoding otherwise, and you can change it later in the complete MPEG file using Restream.

FitCD is a useful tool to help with aspect ratio calculations.
I often use that to create the initial script.


NTSC DVD has to be 720x480 (well, there are other sizes, see https://www.videohelp.com/dvd )

[jagabo]

The crop/resize settings you're using are for DVD. There's no need for that if you're just making videos to play on an iPad. I don't know what limitations the iPad has but you can just proportionally resize the source and use square pixel encoding. It's best to keep mod16 frame sizes so a slight aspect error may be unavoidable. For example, resize to 704x288 instead of 704x290.

Why use MPEG 2 encoding if you're not making a DVD? h.264 encoding will get you better compression.

[AlanHK]

Why use MPEG 2 encoding if you're not making a DVD? h.264 encoding will get you better compression.

There are two people here, one making DVD, one doing iPad.

[jagabo]

Why use MPEG 2 encoding if you're not making a DVD? h.264 encoding will get you better compression.

There are two people here, one making DVD, one doing iPad.

Ah, missed that.