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

[JD]

On 11/03/2010 11:30 AM, JD wrote:
> 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).
>>
> Hi
> I tried  -vf-add dscale=1280:800:0,scale=0:0,expand=::::::16
>
>
> $ mencoder myvid.avi -mf fps=30 -o myvid.mp4 -ovc lavc -lavcopts 
> vcodec=mpeg4 -vf-add dscale=1280:800:0,scale=0:0,expand=::::::16
> MEncoder SVN-r31628-4.4.4 (C) 2000-2010 MPlayer Team
> Option vf-add: dscale doesn't exist.
>
> Exiting... (error parsing command line)
>
I retried like this:

mencoder inception.avi -mf fps=30 -oac lavc -ovc lavc -lavcopts 
abitrate=128 -vf-add scale=1280:800:0,scale=0:0,expand=::::::16 -o 
inception.mp4

This did not work. It yielded  a 4:3 aspect ratio video.