[mythtv-users] Strange X CPU usage for 720p input streams

Michael T. Dean mtdean at thirdcontact.com
Wed Jun 21 01:29:34 UTC 2006

On 06/20/2006 12:40 AM, Indulis Bernsteins wrote:

>>X still has high CPU watching
>>recorded 720p programs.  Not quite sure why that would be.
>Makes sense- 720P sends out 720 lines *every* frame, 1080i sends out 1080 
>lines every 2 frames (ie 540 lines every frame).
Actually, that's 540 lines/field with 2 fields per frame.

>  From a a processing 
>point of view, 720p is like 1440i, so you'd expect about 30% more CPU to 
>decode and cope with the video data coming in.

Of course, 720p60 is 1280x720 pixels/frame @ 60 frames/second = 55296000 
pixels/second.  And, 1080i60 is 1920x1080 pixels/frame @ 30 
frames/second (i.e. 1920x540 pixels/field @ 2 fields/frame @ 30 
frames/second) = 62208000 pixels/second.

Therefore, 720p60 is about 89% as many pixels as 1080i60.  Or, 1080i60 
is 112.5% the number of pixels of 720p60...


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