[mythtv-users] Choppy video at LOW bitrates

nowhere at cox.net nowhere at cox.net
Tue Feb 24 18:54:36 EST 2004

I saw that post about the choppy video with all black screens too and was able to find that old thread by searching on extra audio buffering (never would have thought of that :)

It seems that this plus the jitter reduction flags help the problem with the all one color frames being choppy. I have also noticed this problem and it was number two on my list.

I will try the two flags mentioned tonite and see if it clears it up both issues.

As for the second issue you mentioned, I may have the same problem with "horizontal blips" also. For me it appears that for one frame or so, the horizontal sync is lost.  I haven't seen any threads discussing horizontal sync. We'll see if the two flags help this too.

Thanks for the info.

> From: Tom Marshall <tommy at home.tig-grr.com>
> Date: 2004/02/24 Tue PM 06:09:36 EST
> To: Discussion about mythtv <mythtv-users at mythtv.org>
> Subject: Re: [mythtv-users] Choppy video at LOW bitrates
> 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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