True widescreen perhaps not that true....   

For may years I have been working with the DV-firewrire-Direct/X 
combination. (All figures below are for PAL).
A "normal" (4:3) DV frame is 720*576 pixels.
Last night I had a visitor who brought his Panasonic DV camera equipped 
with "true wide screen" (16:9).
So, I hooked it up to my PC and make a few experiments.(Using my own 
custom capture/playback software)

And to sum it up: Regardless of which mode you set the camera in, you 
always get 720*576 pixels.
However, with the camera in 16:9, the image is visibly compressed X-wise.
A circular object will thus look very elliptical when recorded in 
wide-screen.
So, the camera has a true wide-screen sensor, but it compresses the 
image to the normal 576 pixels width.
There is a flag in the DV metadata (containg timecode etc) that 
indicates that the image is compressed X-wise, and it is then the task 
of the player to read/understand this flag to stretch it.

My conclusion is that if you want to record and analyze athletes like 
tennis players, baseboll hitters or golfers, wide-screen is wasted. You 
will only get more info about the area beside the athlete, and less 
about the athlete himself. (That is if you have the camera in its normal 
orientation)
My brother (the visitor) however loves wide-screen for his "vacation 
style" shooting.

I also captured a short sequence using Windows movie maker (producing a 
DV avi) and played it back using a number of players.
WMP will automatically stretch the picture.
VirtualDub does not stretch.
Quicktime player does not stretch.
VLC media player can't play it at all!(Unrecognized format for 
'C:\Widescreen_test\widescreentest.avi')
Rendering in Graphedit 9 (build 060822) does not stretch
The same goes for Graphedit plus


/Johan

date: Thu, 07 Aug 2008 08:49:10 +0200   author:   Johan Stäck

Re: True widescreen perhaps not that true....   

On Thu, 07 Aug 2008 08:49:10 +0200, Johan Stäck wrote:

> And to sum it up: Regardless of which mode you set the camera in, you 
> always get 720*576 pixels.
> However, with the camera in 16:9, the image is visibly compressed X-wise.
> A circular object will thus look very elliptical when recorded in 
> wide-screen.
> So, the camera has a true wide-screen sensor, but it compresses the 
> image to the normal 576 pixels width.

That is correct.  DVD is the same way as well.  Note that it shouldn't look
quite right if filmed in 4:3 either as 4/3 = 1.333 and 720/576 = 1.25.
Granted that is a lot closer than 1.78 for 16:9.

> I also captured a short sequence using Windows movie maker (producing a 
> DV avi) and played it back using a number of players.
> WMP will automatically stretch the picture.
> VirtualDub does not stretch.
> Quicktime player does not stretch.
> VLC media player can't play it at all!(Unrecognized format for 
> 'C:\Widescreen_test\widescreentest.avi')
> Rendering in Graphedit 9 (build 060822) does not stretch
> The same goes for Graphedit plus

This has been a long standing problem where players don't correctly read
the aspect ratio values.  Many players assume square pixels which is not
always the case.

-- 
http://www.chrisnet.net/code.htm
[MS MVP for DirectShow / MediaFoundation]

date: Thu, 7 Aug 2008 09:33:34 -0400   author:   Chris P.