[mythtv-users] HD Compression Artifacts

Rod Smith mythtv at rodsbooks.com
Fri Mar 23 03:15:40 UTC 2007

On Thursday 22 March 2007 19:50, John Goerzen wrote:
> Hi,
> I have a pcHDTV 3000 and am using it for over-the-air HD broadcasts.
> I have noticed recently that during NCAA games, where there is on-screen
> action -- even some sort of graphic moving around -- that classic MPEG
> compression artifacts are visible around it on the TV.  I have no
> explanation for this.  It seems like with HD, we shouldn't have to deal
> with that sort of thing, yet there it is.

I can't be 100% certain, but I believe what you're seeing is MPEG compression 
artifacts on the transmitting end. HD is just video of a certain resolution. 
If it's compressed too much, compressed using poor-quality equipment, or if 
the video on-screen moves too much, you'll see MPEG compression artifacts, no 
matter what the resolution. (Of course, the bitrate required to avoid 
compression artifacts varies with resolution -- it's higher for HD content 
than for SD content.) If you want to do something about this, your best bet 
is likely to be to complain to the content provider. That might motivate them 
to improve their equipment or to devote more bandwidth to their HD 
broadcasts -- but keep in mind that there are technical limits to digital 
broadcasts (and digital media generally). It's possible that you're sensitive 
enough to these limits to be bothered by them, even with signals that most 
people would consider to be quite good. In my experience, once you've learned 
to see MPEG artifacts, it's hard to ignore them, but most people can't see 
them unless they're pretty awful.

Rod Smith

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