Re: [Mjpeg-users] mpeg2enc: progressive vs interlaced quality

[Dik T. <D.H...@ph...>]

On Fri, 29 Oct 2004, James Bigler wrote:

>>> 	One thing that has worked very well is to use the 1/2 encoded frame
>>> 	size (352x480 for 525line systems and 352x288 for 625line systems).
>> 
>> 
>> 	That should have been 352x576 for 625line systems.   the 352xN is
>> 	a valid DVD frame size that has worked well for me.
>
> Tell me more about this, please.  You can encode an MPEG-2 stream with half 
> the x resolution?  I imagine you have to change the aspect ratio of the file 
> as well, right?

Yes, there are a few possible image resolutions defined by the MPEG-2 
standard. Using half the horizontal resolution has no influence on the 
aspect ratio while playing it. The player will stretch the image to 
720 (or 1024 for widescreen material) horizontal pixels, no matter the 
stored resolution. The player knows how to do this because the desired 
aspect ratio is stored in the MPEG2 stream.

I guess you can see the difference between full and half horizontal 
resolution when encoding widescreen material and display it on a 
widescreen TV, but for 4:3 material, it could indeed work fine.

Dik