[mythtv-users] MythTV channel buffer
wmunson at rochester.rr.com
Fri Apr 14 18:19:34 UTC 2006
From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Felix Rubinstein
Sent: Friday, April 14, 2006 1:37 PM
To: Discussion about mythtv
Subject: Re: [mythtv-users] MythTV channel buffer
I don't compain, it's just the first time I encounter a limitation in Linux!
Once again, I don't want just to watch TV but instead to watch TV under
MythTV, what if I watch TV and switch my receiver to another channel,
instead of seeing the new channel right away, I wait for 4 secs new channel
People don't you ever thought that it's merely a showstopper? My point was
that it's the first time I was shamed Windows outperformed Linux and why,
because no one ever took some time to think about more optimal algorithm.
The most important feature doesn't work correctly, don't you think so, don't
you use S-Video or don't you switch channels? Or I should waste time to
correct the code?
MythTV doesn't know the channel was switched, for it it's just a stream of
bits, all I want is just:
and that this stream to be buffered for me to go forth and back.
How can I use MythTV if I need to wait 4 secs every time I switch to the new
I agree that the current ring buffer implimentation is very very very poor.
On average it take 10-15 seconds for video to appear after starting live tv
and a good 5 seconds for it to change channels. Just for giggles I loaded
windows and one of the commercial pvr packages and was pleasantly surprised
at just how "quick" it was. TV appears in less than a second and channel
changing is about 2 seconds with my ir blaster. Its almost instant when
feeding the RF input of the capture card with OTA signals. Yes it buffers
the video and you can "rewind" for about 30 minutes before it runs out of
buffer. However I lost the ability to transcode to reduce file size plus all
the other useful modules of myth. I guess its up to you. Use a different
program if the delays bother you that much or just go directTV and one of
their free PVR's.
PS - Most people use the browse mode when channel surfing so there is only
one channel change delay to deal with.
IMHO - The problem with myth and buffers is that myth allows the file system
to use the maximum amount of buffering on every disk operation. When you
start video it fully buffers 2 or 3 writes worth of video before committing
it to disk and the frontend has to sit there trying to read the data. It
appears the devs have the frontend set to check for video every second so
there is 2-3 more seconds of blankness before the video is ready even after
the video is present on the hard drive. The way windows systems do this is
backend notifies the frontend as soon as it writes the 1st video
frame/packet and passes along the file location/handle. This eliminates much
of the delays of waiting for the frontend to discover the video is present.
Forcing the disk subsystem to write video packets without buffering would
eliminate most of the other delays. Am I ready to scrap myth? Not quite but
if the windows products get much better I will probably switch.
I still have hope that the devs will get their heads out of their a$$es and
stop denying there is a problem. I know its not as sexy to fix bugs as it is
to code in a neat new feature but its time to take a breath and debug your
code for a few months.
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