[mythtv] Effect of Multi-rec on channel change times....?

Steven Adeff adeffs.mythtv at gmail.com
Thu Jul 19 16:15:48 UTC 2007

On 7/19/07, Ed W <lists at wildgooses.com> wrote:
> > I don't know. All STB's I've used had pretty darn awful
> > channel changing speed considering that they don't need
> > to do the buffering that a PVR does.
> The channel changing moan has come up so many times it would be useful
> to add some instrumentation to the code to track it I think.  I did hack
> in some logging a while back on my own tree and found that there was
> quite a lot of room for improvement, but really it needs to get some
> proper instrumentation in the code so that:
> a) less experienced myth video users such as myself can more easily see
> the code flow during channel change (I found it hard to see how it jumps
> around various threads)
> b) it stops people moaning about areas of slowdown that quite clearly
> aren't an issue and instead helps optimise the areas which will help
> It's quite a long time back now, but I found about 3/4 of a second
> disappearing in waiting on locks (which looked like it could be
> removed), but I struggled to figure out which threads were actually
> causing the holdup.
> Could someone who knows the code better (Daniel?) please consider adding
> in a dozen or so debug logging statements so that we can more easily see
> where the bulk of the time goes in channel changing?  I think there are
> some easy fixups to be had here.

I know it *can be* as fast as the STB's. My Aver A180's tune as
quickly as our Motorola DVR. The Motorola boxes I have connected to
firewire take a little longer because of the problems with firewire
capture in general but within a few seconds at most. Sometimes the
firewire connected box takes longer to pull in a full frame than Myth
takes to grab the firewire stream so you can actually see the picture
building through Myth the same as you do if it were connected to the
TV directly.

of course, livetv wasn't really usable before I went with gigabit
ethernet, after which the whole thing sped up. could be different if
its all on the same machine.


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