[mythtv-users] 25p vs 50p compression was (Re: OT: LED or Plasma (was Advice on choosing a TV))

[Paul Gardiner]

On 25/05/2010 14:37, Andre wrote:
> It turns out it's actually really easy to send high frame rate video so no halfway  houses are really required, 1080p50 needs no more bandwidth than 
1080i50 less sometimes, 1080p300 needs little more than 1080p50, less 
sometimes, when the frames are clear of motion blur and little change to 
the next one they compress really well! As a handy little side benefit 
if there is a lot of sensor noise (which there will be at 300 or 600fps) 
that changes every frame the real picture doesn't so much, so the first 
thing that gets removed in compression is the sensor noise, proper noise 
reduction for free!

I've now confirmed that myself. I've been experimenting with JYA's new
mythtranscode with --fifodir --passthrough piping the result into ffmpeg
using libx264. That for the first time allows me to get good transcodes
of some 1080i content without losing the interlacing. But also I've
been trying scaling down to 720p25 and 720p50. The interesting thing
was how little difference there was between the file sizes for the two:

   720p25   140MB
   720p50   150MB

Tiny difference in file size, but huge difference in motion
quality of course.

Cheers,
	Paul.