[mythtv-users] MythTV channel buffer

Steven Adeff adeffs.mythtv at gmail.com
Sat Apr 15 02:39:02 UTC 2006


On 4/14/06, Greg Estabrooks <greg at phaze.org> wrote:
> > think of that would make a difference:
> > 1. Combined frontend/backend versus seperate
> > frontend/backend - When I was running a seperate f/e
> > machines, I noticed that it took much longer (up to 15
>
>    Certainly this can have an effect,which is why I timed both.
>   From my combined backend+frontend (1.4 seconds to change, 2 to start)
>   and the remote frontend (1.8 seconds to change, 2.3 to start).
>
>   Not even close to the 8-15 seconds some are seeing.
>
> > configuration under 0.19 (though I will be soon).
>
>   I found it quite improved after Isaacs big rewrite.
>
>
> > 2. The CPU speed of the backend and frontend - Faster
> > CPUs will definitely help.
>
>  In my case the backend+frontend is a XP2500+,
> My remote frontends are all diskless nfsrooted machines varying
> in cpu from 733MHZ MSNTV units to 1.2G AMD based pc's
>
> > 3. PCI bus bandwidth/latency - Could it be that the
> > people who are seeing the delays have tons of tuners
>
>  I have 3 tuners in that backend and often are all in use,
> as for what sort of PCI latency settings in use at the moment
> I have no idea. I certainly didn't set anything specific.
>
> > 4. (For seperate f/e setups) - Network latency.
> > 100/1000 Base-T, half/full-duplex, they make a
> > difference.
>
> 10/100 here. Varying nic's on the network.


I don't think the 10seconds are for buffering. They're for background
stuff that mythbackend is processing. Of course, speeding that stuff
up depends on if its issues with the code or hardware.

Really, the buffer does not need to be full before live tv begins to
show. But even the tivo fills its 3sec(or so, i forget what the Tivo's
buffer is) buffer before showing live tv. what differs, and has been
discussed on the dev list but noone has bothered making changes (more
pressing issues) is the perception of the channel change time.

One thing that would help is for the current channel to continue
playing from the buffer until the new channel is ready. This would
eliminate a lot of the perceived time it takes for channel changes.
Hopefully, slowly, as the devs get enough information from us users,
they can optimize other areas of the channel change code so that the
people seeing 10sec channel changes catch up to those of us with ~3sec
changes.

--
Steve


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