[mythtv-users] Pause in image after switch channels...
bjm at lvcm.com
Fri Jul 6 00:48:37 UTC 2007
Nicolas Riendeau wrote:
> Noob here...
> I was wondering if it's normal, after switching channels, to have a
> slight pause in the image when watching live TV...
> The pause is not immaediate, it can take something like 5-10 after I
> have switched channels for it to happen. I used to have it
> occasionally too while watching TV for a while but since I`ve
> upgraded the pc it doesn`t seem to have happened... If I look at the
> same passage again (ie I rewind) the pause is not present...
> The tuner is a PVR-150 MCE and the pc itself if a P5B-Plus with a
> E6600 and the hard disk is a Seagate 7200.10 320 Mb SATA drive...
> I`ve been reading about some possible performance issues with the
> ext3 file system (what the disk is currently formatted with) but the
> issues mentionned problems while deleting file which I'm unsure is
> being done when I switch channels...
Not the issue.
> Is there something I'm doing wrong...
> Please help...
Sure. Record the shows you like and spend your time in front
of the TV watching what you like rather than flipping through
channels hoping to find something 'good'.
For live TV, the signal is digitized, compressed, blocks sent
to the disk, blocks read from disk, uncompressed, queued then
displayed. it takes about 50 (30-70) frames worth data to fill
the pipeline (regardless of how much you've spent on any piece
of hardware, it's the amount of data not the speed of any device).
New users often complain of the 2-3 sec of delay (until they
figure out what they really want to do instead) and therefore
we cut it as close as possible. However, when the scene becomes
static or dark. the video can be compressed more efficiently
and therefore less data is being created and blocks are moved
less frequently until the playback runs out of frames and has
to pause until there are more frames available.
So, after you change channels there is about half a chance that
it will pause at least once in the first few seconds or minute
until you hit pause or rewind. We could increase the delay (number
of decoded frames queued) before playback starts after a channel
change to reduce this effect but people complain much more about
slow channel changes so it is a compromise to start as soon as
possible without causing too many pauses.
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