[mythtv-users] Choppy video at LOW bitrates

Tom Marshall tommy at home.tig-grr.com
Tue Feb 24 18:09:36 EST 2004

On Tue, Feb 24, 2004 at 03:53:17PM -0500, nowhere at cox.net wrote:
> Hi,
> I am experiencing very choppy video and audio on Live TV and recorded (seems like a huge amount of dropped frames) when I reduce the bitrate to 2200 from the default mythtv setup of 4000. If I increase slightly to 3000 the problem is almost gone except with an occassional stutter on a scene change or high speed/dark motion.  At 4000 the video is flawless.
> I am using 0.14 myth, with the recommended ivtv driver versions on a P4 3.0Ghz, 1GB RAM, single PVR250, 80GB Seagate (dma confirmed enabled).  I have only upgraded the kernel according to Axel's recent recommendation to allow apt-get of lirc (I forget the versions, Im at work).  I am at 480x480 resolution for the capture. I have left everything unchanged from the default Myth setup except the sound 32000->48000 and this change of the video bitrate. 
> I'm only running an 80Gig drive so I need to save some space ;)
> I have searched google and the archives and haven't seen anyone else with this problem yet (could be my search string?)
> Anyone have any ideas?

I have the same experience.  Don't know if it's the encoder (ivtv driver) or
decoder (mythtv).  I decided that increasing the bitrate was easier than
trying to find out where the problem is and whether it's fixable.

I also experience some choppy playback when scenes fade to black.  Since you
are using ivtv, you'll probably have the same issue.  A post earlier today
suggested using extra the audio buffering (should be under "Settings", "TV
Settings", "Playback").  I will try this tonight to see if it helps.

Assuming the extra audio buffering works, my only remaining issue is
frequent "horizontal blips" -- part of one frame is overlaid onto the next
frame but offset horizontally by about 1/4 to 1/2 of the screen.

It is by the fortune of God that, in this country, we have three benefits:
freedom of speech, freedom of thought, and the wisdom never to use either.
        -- Mark Twain
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