[mythtv-users] (no subject)

Richard Schelin rks1789 at hotmail.com
Fri Jul 11 06:35:00 EDT 2003 

> > Would I gain in performance by recording as close to the native format 
>as
> > possible...704x480?

>No.  I've never heard of anyone not able to capture at 30fps (or 25fps in 
>PAL
>land) at lower resolutions.

>Isaac

My system has little problem capturing (520x480 Mpeg4 with all the options/ 
mp3 encoding) I'm using about 30-50%cpu time recording, and playing back I 
think it's about 20% or less.

I think the general assumption is that people are using a dedicated system 
to run mythTV, for me this is not the case.  So any gain in performance 
without sacrificing quality is a step in the right direction.

I guess now that I have had time to think the questions I still have are:

1.  What resolution should I record at, so that I don't lose any data, but 
I'm not capturing duplicate data.  I assume that the 480 is fixed, but what 
is the native resolution my capture card is grabbing? (NTSC)  Is it 
different for each card, or is it standard?

2.  What percentage of the processing goes into scaling the images as they 
are captured before encoding them.  I profiled some code at work yesterday 
that I thought had terrible performance....turns out my code is only using 
4% of the total execution time, so optimizing it would be useless....

3.  What resolution do other people record at, and why?  I started out with 
the thought "Bigger is better", the old american Mantra :)  But I can't 
really see too much difference between 540 and 720 (I figured if I 
eventually want to output to my HDTV, 540 is the resolution I want to 
output, so I might as well capture it that way first)

>Shawn Jackson wrote:
>so if wanted the max possible resolution without going overboard on ntsc 
>what should i set my res >to? right now i have it and my capture card at 
>720x480 but my file sizes are a whopping 3.6 GB / >hour with mpeg4 @ 2200

Good question.  And I would like to make a note that I'm sure has been all 
over the place, but it can't hurt :)  The cable I have coming to my computer 
is flakey, and sometimes I get some static when I record.  When this happens 
my file size jumps from 860MB/hour to the worst I had once was something 
like 2600MB/hour.  This was due to the fuzzy/static nature of the capture.  
The compression algorithm (I'm assuming I've never really red the mpeg4 
spec, but most of them work in similar fashion) looks for repeating 
colors/patterns and gets rid of the extra information.  I never would have 
thought that there was such a difference between a clean signal and a 
"dirty" one.

Thanks!

Rich










----Original Message Follows----
From: mythtv-users-request at snowman.net
Reply-To: mythtv-users at snowman.net
To: mythtv-users at snowman.net
Subject: mythtv-users Digest, Vol 6, Issue 42
Date: Thu, 10 Jul 2003 21:51:38 -0400

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When replying, please edit your Subject line so it is more specific
than "Re: Contents of mythtv-users digest..."
Today's Topics:

    1. RE: MythGallery: Rotating images (Joseph A. Caputo)
    2. Re: MythGallery: Rotating images (Jim Paris)
    3. Re: Archive Tv Shows (Rob Snow)
    4. Re: Archive Tv Shows (Will Dormann)
    5. standard capture size? (Richard Schelin)
    6. Re: standard capture size? (Isaac Richards)
    7. Re: Archive Tv Shows (Chris Petersen)
    8. RE: Re: Quiet Power Supplies/Quiet PC's (Rex Young)
    9. MythGame -- xmame problem? (Kevin Gibbons)
   10. RE: Re: Quiet Power Supplies/Quiet PC's (Shirley, Mark R)
   11. Re: MythGame -- xmame problem? (Jason Lowdermilk)
   12. RE: MythGame -- xmame problem? (Joseph A. Caputo)
   13. optimize MythTV (William Lindner)
   14. Re:MythGame -- xmame problem? (Kevin Gibbons)
   15. Re: Re:MythGame -- xmame problem? (Isaac Richards)
   16. Sound Blaster Live! and capturing issues... (Jay Camp)
   17. Re: optimize MythTV (Albert Santoni)
   18. Re:standard capture size? (Shawn Jackson)
   19. Re: Channel Changing not working (Jeff Waters)
   20. Re: optimize MythTV (Nathan Poznick)
   21. Re: Channel Changing not working (Isaac Richards)
   22. How to upgrade my computer? (Keir Christian Lauritzen)
   23. [mythtv-users]Help on w/2 modules and a tv-out/overscan
       question (Mike Miller)
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