[MPlayer-users] question concerning DAR and PAR

[belcampo]

Steven Miller wrote:
> 
> You hit the nail on the head. I have to create video to be streamed from a
> Darwin streaming server to quicktime clients. I'm only shooting for 'good'
> quality as streaming via 'wireless' is another requirement. 
> 
> I'm still not sure about,
> 	704x480 (DAR 1.74) scaling to 836x480 on playback. Does this
> resizing 
> 	Keep the 1.74 ratio or is it resizing to a resolution that provides
> square pixels? Maybe both?
> 
> I know I can look up the PAR for common dvd's
> "http://en.wikipedia.org/wiki/Pixel_aspect_ratio" easily enough.
> 
> How would I find the PAR for my 704x480 with a DAR of 1.74:1?
ffmpeg -i source.ext
example:
Video: mpeg2video, yuv420p, 704x576 [PAR 16:11 DAR 16:9], 10000 kb/s, 25 
tbr, 90k tbn, 50 tbc
It will display at 1024x576
Or mediainfo which is an app which give a whole lot of info
> 
> Thanks for your help with this. I'm under the gun to get this going. Once I
> get el capitan off my back, I'll be able to take the time to learn without
> annoying people ;-)
> 
> Steve
> 
> 
> -----Original Message-----
> From: mplayer-users-bounces at mplayerhq.hu
> [mailto:mplayer-users-bounces at mplayerhq.hu] On Behalf Of belcampo
> Sent: Wednesday, November 25, 2009 7:03 AM
> To: MPlayer usage questions, feature requests,bug reports
> Subject: Re: [MPlayer-users] question concerning DAR and PAR
> 
> belcampo wrote:
>> Steven Miller wrote:
>>> I have a dvd (ntsc 740x480) that crops to 704x480 (704:480:8:0) which
>>> changes the DAR from 1.78:1 to 1.74:1. The resulting resolution (on
>>> playback) ends up being 836x480. Before anyone asks, I have been reading,
>>> but it's lot to absorb! If I understand correctly, 836x480 maintains the
>>> 1.74:1 ratio?  Another question is, 1.74 indicates a non square pixel,
>>> doesn't your typical monitor use square pixels? I'm confused as to what's
>>> happening here.
>>>
>>> If I wanted square pixels, would using the 'dsize' filter with a 
>>> resolution
>>> that is divisible by 16 (scale=-1:-10,dsize=704:400 (this ends up with a
>>> resolution of 704x400 and a 1.76:1 ratio)) give me square pixels, while
>>> maintaining a mathematically and visually correct encode?
>> dsize=704:400 will do this.
>> Almost all video-sources were/are meant to play on TV, where AFAIK NEVER 
>> square pixels are used, as in your DVD-example. Square pixels will 
>> result in more pixels without ANY benefit.
> Another point, if square-pixels is needed, and 400 is not a limit 
> somehow, is that reducing vertical pixels reduces percepted quality more 
> then horizontal. So for max square-pixel quality you would use the full 
> 836:480 values
>> Only if you need to play on devices that don't accept, iPod and others, 
>> non-square pixels it's usefull/necessary to use square-pixels.
>>>  
>>>
>>> Thanks in advance!
>>>
>>>  
>>>
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