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Myth very slow to change channels.... (DVB-T)

 

 

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jyavenard at gmail

Aug 25, 2008, 4:14 PM

Post #1 of 27 (8344 views)
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Myth very slow to change channels.... (DVB-T)

Hi

It takes over 6s to go from watching one channel to another...

I've changed all options that I thought would help (like aggressive
sound card buffer; etc)...

mythfrontend seems to buffer an awful amount of data before showing
anything ; I can tell as when I kill the backend process mythfrontend
continue playing the video for several seconds before it freezes...

Any ideas what to do to speed things up?

Thanks
JY
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myth at dermanouelian

Aug 25, 2008, 4:40 PM

Post #2 of 27 (8280 views)
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Re: Myth very slow to change channels.... (DVB-T) [In reply to]

On Aug 25, 2008, at 4:14 PM, Jean-Yves Avenard wrote:

> Hi
>
> It takes over 6s to go from watching one channel to another...
>
> I've changed all options that I thought would help (like aggressive
> sound card buffer; etc)...
>
> mythfrontend seems to buffer an awful amount of data before showing
> anything ; I can tell as when I kill the backend process mythfrontend
> continue playing the video for several seconds before it freezes...
>
> Any ideas what to do to speed things up?

Oh, thank goodness. It's been ages since we've had this thread. Let
the games begin....

Just to add a tiny bit of value to my post:
Frontend does not buffer. As soon as the data becomes available for
playing, it plays.
Check previous posts. There have been hundreds, at least.

-Brad

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jyavenard at gmail

Aug 25, 2008, 5:03 PM

Post #3 of 27 (8275 views)
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Re: Myth very slow to change channels.... (DVB-T) [In reply to]

Hi

2008/8/26 Brad DerManouelian <myth [at] dermanouelian>:
> Just to add a tiny bit of value to my post:
> Frontend does not buffer. As soon as the data becomes available for
> playing, it plays.

How do you explain that when I kill mythbackend ; the frontend client
will continue to play for over 5s ?
this can only be done if buffering happened.

> Check previous posts. There have been hundreds, at least.
I did... many reported problems , no solution in sight
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mythtv at hotblack

Aug 25, 2008, 5:11 PM

Post #4 of 27 (8288 views)
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Re: Myth very slow to change channels.... (DVB-T) [In reply to]

Jean-Yves Avenard wrote:
> Hi
>
> 2008/8/26 Brad DerManouelian <myth [at] dermanouelian>:
>> Just to add a tiny bit of value to my post:
>> Frontend does not buffer. As soon as the data becomes available for
>> playing, it plays.
>
> How do you explain that when I kill mythbackend ; the frontend client
> will continue to play for over 5s ?
> this can only be done if buffering happened.

As Brad says mythfrontend does not buffer the data. The backend buffers
a little before writing to the recording file, as does the OS/filesystem
itself.

- Wade
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jyavenard at gmail

Aug 25, 2008, 5:30 PM

Post #5 of 27 (8286 views)
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Re: Myth very slow to change channels.... (DVB-T) [In reply to]

Hi

2008/8/26 Wade Maxfield <mythtv [at] hotblack>:
> As Brad says mythfrontend does not buffer the data. The backend buffers
> a little before writing to the recording file, as does the OS/filesystem
> itself.

That can't be the explanation... As soon as you kill mythbackend it is
unable to continue streaming obviously.

If mythfrontend didn't buffer data it would stop immediately when
mythbackend is stopped which isn't the case
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bill at bbqninja

Aug 25, 2008, 5:35 PM

Post #6 of 27 (8281 views)
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Re: Myth very slow to change channels.... (DVB-T) [In reply to]

On Tue, Aug 26, 2008 at 10:30 AM, Jean-Yves Avenard <jyavenard [at] gmail> wrote:
> Hi
>
> 2008/8/26 Wade Maxfield <mythtv [at] hotblack>:
>> As Brad says mythfrontend does not buffer the data. The backend buffers
>> a little before writing to the recording file, as does the OS/filesystem
>> itself.
>
> That can't be the explanation... As soon as you kill mythbackend it is
> unable to continue streaming obviously.
>
> If mythfrontend didn't buffer data it would stop immediately when
> mythbackend is stopped which isn't the case

Do you have your recordings directory shared with NFS?
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mythtv at hotblack

Aug 25, 2008, 5:38 PM

Post #7 of 27 (8285 views)
Permalink
Re: Myth very slow to change channels.... (DVB-T) [In reply to]

Jean-Yves Avenard wrote:
> Hi
>
> 2008/8/26 Wade Maxfield <mythtv [at] hotblack>:
>> As Brad says mythfrontend does not buffer the data. The backend buffers
>> a little before writing to the recording file, as does the OS/filesystem
>> itself.
>
> That can't be the explanation... As soon as you kill mythbackend it is
> unable to continue streaming obviously.
>
> If mythfrontend didn't buffer data it would stop immediately when
> mythbackend is stopped which isn't the case

I don't think so. As soon as you kill mythbackend, the filesystem
should flush any remaining data remaining to be written, which
mythfrontend can then play. That would account for some of the extra
time that the frontend continues to play.

- Wade

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jyavenard at gmail

Aug 25, 2008, 5:46 PM

Post #8 of 27 (8269 views)
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Re: Myth very slow to change channels.... (DVB-T) [In reply to]

Hi

2008/8/26 Bill Williamson <bill [at] bbqninja>:
> Do you have your recordings directory shared with NFS?

I do ; however the option is set to always stream from mythbackend.
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jyavenard at gmail

Aug 25, 2008, 5:47 PM

Post #9 of 27 (8283 views)
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Re: Myth very slow to change channels.... (DVB-T) [In reply to]

Hi

2008/8/26 Wade Maxfield <mythtv [at] hotblack>:
> I don't think so. As soon as you kill mythbackend, the filesystem
> should flush any remaining data remaining to be written, which
> mythfrontend can then play. That would account for some of the extra
> time that the frontend continues to play.

no ; mytthfrontend is configure to always stream from the backkend

as such the frontend isn't influenced by what filesystem is in use in any way
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myth at dermanouelian

Aug 25, 2008, 5:53 PM

Post #10 of 27 (8281 views)
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Re: Myth very slow to change channels.... (DVB-T) [In reply to]

On Aug 25, 2008, at 5:47 PM, Jean-Yves Avenard wrote:

> Hi
>
> 2008/8/26 Wade Maxfield <mythtv [at] hotblack>:
>> I don't think so. As soon as you kill mythbackend, the filesystem
>> should flush any remaining data remaining to be written, which
>> mythfrontend can then play. That would account for some of the extra
>> time that the frontend continues to play.
>
> no ; mytthfrontend is configure to always stream from the backkend
>
> as such the frontend isn't influenced by what filesystem is in use
> in any way

Yeah, we're lying to you. Set the frontend's buffer to 0 instead of 5
seconds in the code and let me know how that works out for you.


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jyavenard at gmail

Aug 25, 2008, 6:20 PM

Post #11 of 27 (8253 views)
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Re: Myth very slow to change channels.... (DVB-T) [In reply to]

Hi

2008/8/26 Brad DerManouelian <myth [at] dermanouelian>:
> Yeah, we're lying to you. Set the frontend's buffer to 0 instead of 5
> seconds in the code and let me know how that works out for you.

how constructive ...

All I'm saying is that your comment doesn't reflect the behaviour of
mythfrontend at all...
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bill at bbqninja

Aug 25, 2008, 6:59 PM

Post #12 of 27 (8257 views)
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Re: Myth very slow to change channels.... (DVB-T) [In reply to]

On Tue, Aug 26, 2008 at 10:46 AM, Jean-Yves Avenard <jyavenard [at] gmail> wrote:
> Hi
>
> 2008/8/26 Bill Williamson <bill [at] bbqninja>:
>> Do you have your recordings directory shared with NFS?
>
> I do ; however the option is set to always stream from mythbackend.

I've never had that option work to be honest if they are available via NFS.

Unmount your NFS and test again.
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jyavenard at gmail

Aug 25, 2008, 7:03 PM

Post #13 of 27 (8264 views)
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Re: Myth very slow to change channels.... (DVB-T) [In reply to]

Hi

2008/8/26 Bill Williamson <bill [at] bbqninja>:
> I've never had that option work to be honest if they are available via NFS.
>
> Unmount your NFS and test again.

I'll try that option then ..

When watching a recording ; playback starts instantly ; it's just
changing channels that takes a long time
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dean.harding at dload

Aug 25, 2008, 7:10 PM

Post #14 of 27 (8243 views)
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Re: Myth very slow to change channels.... (DVB-T) [In reply to]

Jean-Yves Avenard wrote:
> When watching a recording ; playback starts instantly ; it's just
> changing channels that takes a long time

See:
http://www.mythtv.org/wiki/index.php/Frequently_Asked_Questions#When_using_live_TV.2C_why_is_there_a_delay_between_the_moment_I_change_the_channel_and_the_time_the_channel_actually_changes.3F

And also try:
http://www.gossamer-threads.com/lists/engine?list=mythtv&do=search_results&search_forum=forum_2&search_string=change+channel+slow&search_type=AND

Dean.

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myth at dermanouelian

Aug 25, 2008, 7:34 PM

Post #15 of 27 (8265 views)
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Re: Myth very slow to change channels.... (DVB-T) [In reply to]

On Aug 25, 2008, at 6:20 PM, Jean-Yves Avenard wrote:

> Hi
>
> 2008/8/26 Brad DerManouelian <myth [at] dermanouelian>:
>> Yeah, we're lying to you. Set the frontend's buffer to 0 instead of 5
>> seconds in the code and let me know how that works out for you.
>
> how constructive ...
>
> All I'm saying is that your comment doesn't reflect the behaviour of
> mythfrontend at all...

The code doesn't support your theory. You said yourself that you
searched and found many threads about this subject and not a single
solution. There is a reason for that.

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jyavenard at gmail

Aug 25, 2008, 7:42 PM

Post #16 of 27 (8258 views)
Permalink
Re: Myth very slow to change channels.... (DVB-T) [In reply to]

Hi

2008/8/26 Bill Williamson <bill [at] bbqninja>:
> I've never had that option work to be honest if they are available via NFS.
>
> Unmount your NFS and test again.

Well, happy to report that it nearly halves the change time ....
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jyavenard at gmail

Aug 25, 2008, 7:43 PM

Post #17 of 27 (8248 views)
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Re: Myth very slow to change channels.... (DVB-T) [In reply to]

Hi

2008/8/26 Brad DerManouelian <myth [at] dermanouelian>:
> The code doesn't support your theory. You said yourself that you
> searched and found many threads about this subject and not a single
> solution. There is a reason for that.

There is slow ; and there's "too slow" ..

6s makes it very painful
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beww at beww

Aug 25, 2008, 7:57 PM

Post #18 of 27 (8256 views)
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Re: Myth very slow to change channels.... (DVB-T) [In reply to]

Jean-Yves Avenard wrote:
> Hi
>
> 2008/8/26 Brad DerManouelian <myth [at] dermanouelian>:
>> The code doesn't support your theory. You said yourself that you
>> searched and found many threads about this subject and not a single
>> solution. There is a reason for that.
>
> There is slow ; and there's "too slow" ..
>
> 6s makes it very painful

Not for me. My changes aren't that slow, but it wouldn't bother me if
they were. I hardly ever watch live TV, and even when I do, browse mode
allows me to see what's on without changing the channel, as does the
program guide on-screen. No reason to change channels often.

It does take 4 or 5 seconds when switching from a cable to a satellite
channel (different capture cards, obviously), much faster just changing
RF channels on the same card.

From the past threads it seems to be an issue with a minority of users.
I think we all tend to watch less and less live stuff as we get more
used to Myth. Why on earth would I want to watch something with
commercials, at a fixed 1X speed ???

beww
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andrew at migmog

Aug 26, 2008, 12:46 AM

Post #19 of 27 (8230 views)
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Re: Myth very slow to change channels.... (DVB-T) [In reply to]

2008/8/26 Brian Wood <beww [at] beww>:
> Why on earth would I want to watch something with
> commercials, at a fixed 1X speed ???
>
> beww

In some parts of the civilized world, live TV comes without
commercials. We also have quality programming where half of the show
is not hooks and recaps for all the channel hoppers.

This (channel switching time) is the main reason I bought a commercial
PVR when my frontend died. One day I will try to fix it, because apart
from this, myth is superior.

mig
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jon.the.wise.gdrive at gmail

Aug 26, 2008, 2:02 AM

Post #20 of 27 (8237 views)
Permalink
Re: Myth very slow to change channels.... (DVB-T) [In reply to]

On Tue, Aug 26, 2008 at 12:46 AM, migmog <andrew [at] migmog> wrote:
> 2008/8/26 Brian Wood <beww [at] beww>:
>> Why on earth would I want to watch something with
>> commercials, at a fixed 1X speed ???
>>
>> beww
>
> In some parts of the civilized world, live TV comes without
> commercials. We also have quality programming where half of the show
> is not hooks and recaps for all the channel hoppers.

Hooks and recaps? Like the first and last minute of most US primetime
shows? the average half hour show is only 22 minutes anyway. But we do
have PBS. I must say though, with the increase in channels, I've seen
a decrease in quality shows on all of them. Gotta love stockholders
and their huge dividends. Probably the downfall of a great many
corporations. Guess that I'm getting a bit off topic now though.

> This (channel switching time) is the main reason I bought a commercial
> PVR when my frontend died. One day I will try to fix it, because apart
> from this, myth is superior.

And this is something that will never get full agreement.
Channel surfers, by definition, are wasting time. If they wanted to
see particular shows, they would schedule the recordings, and watch
them when was most convenient for them, (be it right now - it's
recording, or later when said people had free time) rather than when
they air. This is the reason I think that most people look for a PVR.
Sure, rewinding a live sportscast is cool too, but it isn't a driving
reason I would desire a PVR device.

So, to recap the millions of responses to this question. (I'll save
you a trip to the archive) Don't watch live tv. Flip through the
program guide, set the recordings that you want to actually watch, and
go find something else to do, or watch something else you've recorded.
This isn't the answer you want. It wasn't the answer I wanted when I
was trying to make that change faster for the other users of my myth
system either... but after some contemplation, it really is the best
answer. There are technical difficulties in the recording/channel
changing process that cannot easily be overcome by software. Most
industrial PVRs solve this problem with special hardware.

If you don't like that answer, you have 3 options.

a) don't use mythtv (or don't use it to watch live tv)*
b) figure out how to make the software more efficient (though, you
will find limitations)
c) buy a commercial PVR and pay their outrageous monthly fees to have
instant channel changing and limited space and features.

*(with a, you could do what I did, and split the coax, so they can
channel flip to their hearts content on a true 'live tv', and if they
really wanted to save something, set it to record later on, in myth. I
have found that there are very few shows that aren't aired at least a
couple times, so this solution works especially well for many
'flippers')

I don't foresee channel flipping speeding up much in myth any time
soon. There isn't any demand for it from any of the developers, and
the general users that want it are unable to program. Also, it seems
like one of those things that people just forget about as they get
more used to using myth the way the developers intended, and not like
a basic PVR.

~Jon
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andrew at migmog

Aug 26, 2008, 3:33 AM

Post #21 of 27 (8214 views)
Permalink
Re: Myth very slow to change channels.... (DVB-T) [In reply to]

2008/8/26 Jonny B <jon.the.wise.gdrive [at] gmail>:
> c) buy a commercial PVR and pay their outrageous monthly fees to have
> instant channel changing and limited space and features.
>

Eh? I just bought the PVR (Topfield 5800) and plugged it in. No fees.
The user interface is not as nice as myth, but it can switch channels
in milliseconds, and has ample space for my needs.
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lindsay.mathieson at optusnet

Aug 26, 2008, 3:39 AM

Post #22 of 27 (8230 views)
Permalink
Re: Myth very slow to change channels.... (DVB-T) [In reply to]

On Tuesday 26 August 2008 09:40:59 Brad DerManouelian wrote:
>
> Oh, thank goodness. It's been ages since we've had this thread. Let
> the games begin....

Oh! oh! I got an idea! - why don't we dedicate a tuner to the LiveTV player!

::ducks and runs::

But seriously - JY, the reason channel changes are so slow is that the LiveTV
plugin is basically a frontend to the recording service - viewing channel live
actually schedules a recording via mythbackend for that channel and that time,
which involves tuning a tuner and buffering at least 2 seconds of airtime.
Changing channels repeats the whole process.

This is because LiveTV is almost a afterthought - mythtv is primarily a
scheduling/recording/playback service and this isn't going to change.

Cheers,


--
Lindsay Mathieson
http://members.optusnet.com.au/~blackpaw1/album
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jyavenard at gmail

Aug 26, 2008, 4:16 AM

Post #23 of 27 (8219 views)
Permalink
Re: Myth very slow to change channels.... (DVB-T) [In reply to]

Hi

2008/8/26 Lindsay Mathieson <lindsay.mathieson [at] optusnet>:
>
> This is because LiveTV is almost a afterthought - mythtv is primarily a
> scheduling/recording/playback service and this isn't going to change.

Well, is that a good enough reason to accept how it's behaving then ? :)
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linuxdreas at dslextreme

Aug 26, 2008, 4:49 AM

Post #24 of 27 (8206 views)
Permalink
Re: Myth very slow to change channels.... (DVB-T) [In reply to]

Am Dienstag, 26. August 2008 03:33:06 schrieb migmog:
> 2008/8/26 Jonny B <jon.the.wise.gdrive [at] gmail>:
> > c) buy a commercial PVR and pay their outrageous monthly fees to have
> > instant channel changing and limited space and features.
>
> Eh? I just bought the PVR (Topfield 5800) and plugged it in. No fees.
> The user interface is not as nice as myth, but it can switch channels
> in milliseconds, and has ample space for my needs.

I think, Jon was referring to PVR/DVR's in the US. It is sometimes a little
challenging to keep in mind that the world does not end at the US borders.

--
Gruß
Andreas
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beww at beww

Aug 26, 2008, 7:38 AM

Post #25 of 27 (8205 views)
Permalink
Re: Myth very slow to change channels.... (DVB-T) [In reply to]

Andreas wrote:
> Am Dienstag, 26. August 2008 03:33:06 schrieb migmog:
>> 2008/8/26 Jonny B <jon.the.wise.gdrive [at] gmail>:
>>> c) buy a commercial PVR and pay their outrageous monthly fees to have
>>> instant channel changing and limited space and features.
>> Eh? I just bought the PVR (Topfield 5800) and plugged it in. No fees.
>> The user interface is not as nice as myth, but it can switch channels
>> in milliseconds, and has ample space for my needs.
>
> I think, Jon was referring to PVR/DVR's in the US. It is sometimes a little
> challenging to keep in mind that the world does not end at the US borders.
>
I agree that this list at times is somewhat US-centric. This shouldn't
be surprising since the initial development was done by yanks, but all
of us should try and remember it is a global project.

At least in the US, browse mode or the program guide is a much better
way to find out what's on the other channels than channel surfing, since
there is a high probability of landing on a commercial when you switch
to another channel.

You can't blame developers for not wanting to work on a "problem" that
doesn't bother them. If you really want fast channel switching just
watch your TV set directly, and use Myth only to record.

beww

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