[MPlayer-users] BPP for Frame Size

[Alexander Strange]

On Jan 19, 2007, at 7:18 PM, Jason Tackaberry wrote:

> On Fri, 2007-01-19 at 18:15 +0000, Mark Himsley wrote:
>> Because of the chosen sampling frequency (13.5Mhz) and the active  
>> line
>> length (52us) actually only 702 pixels are active, the 9 at each  
>> end of the
>> lines are not part of the 16:9 picture.  Have you noticed that  
>> most 720x576
>> pictures have thin black bars at the edges - these are the 9 extra  
>> pixels
>> at each edge.
>>
>> If you are going to scale up to 1024x576 you should crop the extra 18
>> pixels off or you will get pictures squished by about 2.5%
> ...

> Anyway, I have to say that this information is quite news to me.  If
> correct (and assuming I am grokking it properly), it would imply that
> all the software DVD players I've seen, including mplayer, are
> outputting video at the wrong aspect ratio.  Do you know if the
> situation is the same with NTSC -- and if so, what are the  
> corresponding
> pixel aspects?  Do you have any further references that discuss this?

http://lipas.uwasa.fi/~f76998/video/conversion/

mplayer is wrong; I've been meaning to bring it up for a while, but  
never got around to it.

When encoding from NTSC DVD, I do:

mencoder -vf pullup,crop=704:480:8:0,scale=640:480

(for 4:3, obviously).

For not scaling, I use dsize=704:528 and autoaspect in the encoder  
options. This makes Xvid report "10/11 (ntsc43)" as the PAR, rather  
than "8/9 (ext)" as with the default AR.

Widescreen isn't mentioned on that page, but the correct size for  
704x480 is 854x480 as you'd expect.