[MPlayer-users] Transcoding from one aspect ratio to another

[JD]

On 11/03/2010 10:59 AM, Krzysztof Duchnowski wrote:
> On 03.11.2010 17:55, JD wrote:
>
>>>> I have a video file that has an aspect ratio of
>>>> 2.353 : 1
>>>> I would like to transcode it to an aspect ratio
>>>> of 1.6 : 1 (like 1280x800).
>>>> Is this even possible?
>>>>
>>> I assume you do not want to skew the picture, just change the
>>> resolution? If so, just -vf scale= will do that for you and figure out
>>> the proper aspect ratio itself.
>>>
>> Yes - you assume correctly. Thank you Rolf. I will try it.
> First of all, dscale is better - you give max resolution and it is
> rescaled properly, but virtually. After that you mut scale it with scale
> but no guessing of resolution.
> I had that problem with script that need to scale DAR(1.33:1)/SAR(1:1),
> DAR(1.77:1)/SAR(1:1) and DAR(1.33:1)/SAR(1:1.33) (anamorphic, displayed
> DAR=1.77) videos to 1.77:1 screen (MP4 for Android phone) without hand
> made optimization every time - example for you:
>
> -vf-add dscale=1280:800:0,scale=0:0,expand=1280:800
>
> This is for maitaining SAR. If you don't want to use bitrate for
> encoding black border then it is enough to expand to power of 16:
>
> -vf-add dscale=1280:800:0,scale=0:0,expand=::::::16
>
> If you change DAR of video wihtout maitaining SAR then it will squeze it
> verticaly or horizontaly (depend of source material).
>
> So, when changing DAR 2.352:1 video (1920x816) to DAR 1.6:1 video
> (1280x800) you must either crop it or expand with black borders to
> maintain SAR/PAR (pixel aspect ratio - square pixel, no squeze).

Thank you Krzysztof. I understand.
I am very disappointed that the original was encoded in 2.353:1
I see that if I want to prevent objects from being squeezed, then
I have to either crop from left and right or accept black boarders.

Best regards,

JD