[mythtv-users] Sound jerkiness with latest RedHat kernel

[Bruce Markey]

Craig Longman wrote:
> Matt wrote:
> 
>> What do you consider "jerky" and "choppy"  ??
>>
> every second or so the audio stops for a little bit (<1/10 of a second 
> perhaps). the video also seems to pause for an equally short period. the 
> problem may only be with one or the other, and then the other one just 
> pausing to resync, i'm not sure.  that's what i consider 'choppy'.

Right. This is usually a pause to straiten out things in
the buffers. It's not that there aren't enough megs of data
in the pipe, it's when things don't happen in quite the right
order for the next frame to be ready in time. This is one
distinct type of problem, the audio cuts out and the picture
freezes for a fraction of a second.

>> I found the best test is to watch CNN and watch the scroll.  I have now
>> noticed that the scroll jerks every 20 - 30 seconds.  I am going to
>> recompile a vanilla kernel from kernel.org and see what happens.
>>  
>>
> thats a little different.  i notice minor jerks like that on cnn now 
> much less frequently, with the latest experimental + jitter reduction 
> code.  it had been much more jerky before that, so much so that i turned 
> off the overlay, preferring the odd bit of tearing from the jerking i 
> was seeing.  but now i have turned it back on and am pleased.  my system 
> still jerks the cnn scroller more that i would like (maybe every 3-5 
> seconds), but its way, way better.

This is the problem of trying to update the frame for the
graphics card at just the right time so that there is a
one to one relationship between the frames and the screen
refreshes. This despite a multiuser scheduler where other
process may want the CPU when the frontend needs it. When
there are misses, there is no update for one frame then two
updates for the next. The audio is continuous but the CNN
crawler will have nervous twitches.

> that's mytechnical definitions for 'jerky' and 'choppy' at least.  :-)

Good job. I followed exactly what you meant =).

--  bjm