[mythtvnz] Channel change stability issues with MythTV and VDPAU in NZ

[Steve V]

________________________________
From: Steven Ellis <steven at openmedia.co.nz>
To: MythTV in NZ <mythtvnz at lists.linuxnut.co.nz>
Sent: Sunday, 7 June, 2009 11:18:05 PM
Subject: Re: [mythtvnz] Channel change stability issues with MythTV and VDPAU in NZ



On 7/06/2009, at 7:56 PM, Jean-Yves Avenard wrote:

Hi

2009/6/7 Steven Ellis <steven at openmedia.co.nz>:

I still get the occasional "Error was encountered" while changing channels,

but I haven't had a crash yet..

I think I've identified what the problem could be.

Haven't looked in that code there, but from some error messages I saw,
I wouldn't be surprised if that was the reason.

So, a mythfrontend tries to watch LiveTV
mythbackend kicks the capture card and start a recording
mythfrontend now waits for that recording to be available for a set
period of time
once the recording has buffered enough and is available, mythfrontend
starts playback

Now when you change channel quickly: it goes on like this:
mythfrontend tries to watch LiveTV
mythbackend kicks the capture card and start a recording
mythfrontend now waits for that recording to be available for a set
period of time
mythfrontend change channel
wait time above lapsed start to try watching the new recordings which
doesn't exist yet: failure

When changing channel very fast, a few times I saw in the log that
buffering time had lapsed and then an error that a given recording
didn't exist.

As the mythtv developers do not use LiveTV, I'm guessing they never
really looked at this issue.



I'll reply on list this time..

You have described the extreme case which I usually include in my stress tests, but at the moment I'm doing the following.

1. Start Live TV

2. Make sure I'm on a freeview|HD only channel - I have freeview's SD DTH service and their DTT freeview|HD service on the same box.

3. Wait for video playback

4. Change to another channel - could be HD or SD

5. Goto 3

So on every channel change I wait, sometimes upto 10 seconds, for the video playback to start.

Steve



Steven Ellis - Technical Director
OpenMedia Limited
email   - steven at openmedia.co.nz
website - http://www.openmedia.co.nz

I tried this the other day. I hadn't posted my results because I was going to put together a list of hardware and software for comparison. I only have Freevoew HD via a Nova - T dual tuner.

Anyway, I did exactly as you above, I managed to change channels 20 times without any problems. I didn't see any need to keep trying.

let me know if you would like me to post my hardware and software setup.

Cheers
Steve