I know I'm new but couldn't find an answer to my question so I thought I'd ask people that know.
I am using Adobe Premiere Pro CS5. The output codec is MainConcept H.264 in an MP4 container.
I have been playing with making 1920x1080p30 by:
Using 1920x1200p30 source video, setting the sequence settings to 1920x1080p30 and then just encoding 1080p that way. High@L4.1, 1920x1080p30. That works just fine. It cuts 60 pixels top and 60 bottom which is fine for what I want. Looks nice and sharp.
I have been thinking of making both 1920x1200p30 AND 1920x1080p30 video using the same sequence and found how to do it:
Make the sequence 1920x1200p30.
Import the video, etc.
Go to export, select High@5.0, 1920x1200p30 and export. Again, everything is perfect. I get what I want
Now, to do the 1080p30 I thought of simply setting 1920x1080p30, clicking "Source", Setting manual crop to 60px top, 60px bottom and it should in my world encode it then as a nice full frame 1920x1080p30 - but it doesn't, it adds black borders. So I go in to settings and set it to Scale to Fit instead.
Now here's my thought... Scale?
Why would it need to scale the video? The video is indeed in 1920x1200 BUT I have cropped the source to 1920x1080. If I select Scale to Fit it encodes nicely and all but... Has it really scaled it?
Does it do the following:
Take the source video.
Crop it to 1080 height.
Scale (but since it's correct it doesn't actually scale anything)
Take the source video.
Scale it to 1744x1080
Apply the crop (which removes 54pixels from the top and bottom).
Scale it to 1920x1080
If it's 1), why do I have to select the "Scale" option for me not to get black borders on all sides? (Yes, all 4 sides). If 2) Why on earth would it do that? That's a loss of quality.
If you're still awake and know what Premiere does, please let me know.
Ok, I've run a few tests. Took the same source, etc and this time I made the output 160x90 pixels large with appropriate cropping.
My idea was that if 2) is true it would look really blurry, or well be totally impossible to see what's there since it scales 1920x1200 => 160x90 and then back, and crops it and if it's 1) then it would be all sharp and nice.
The result is that my video is sharp and nice. So my conclusion is that it does 1), ie it crops it, scales it (without actually scaling since source video and output video match) and then encodes it.
If anyone in the know has any other explanation or maybe show me why my test is wrong, feel free to butt in.
EDIT: Added which codec I use.