Hi,

Just finished building my mythtv PVR some days ago. My setup is detailed in my sig below. It all works okay (for the most part). One thing is a bit of a bother though. It takes mythtv a rather long time to change a channel (4-5 secs at least, during which time the screen frame-freezes the running picture). At first, I changed the cache and myth partitions to xfs filesystems as per this howto :

http://knoppmythwiki.org/index.php?page ... tem+switch

but that made no difference. It looks like a hardware performance issue, but I was running top while I changed channels and saw no noticable rise in CPU load or RAM usage (though I was running back and forth from my remote shell to my tv and may have missed it). I'd be grateful if somebody could offer some insight as to where the hardware falls short. The BIOS supports up to 384 Mb RAM and I have 256Mb.


Thanks for your attention,
AR

Sorry, forgot to include my sig. My system is detailed in my sig below

_________________
My knoppmyth system:
P-III 850 MHz
256 Mb RAM
Hauppauge PVR-350 connected to tv via tv-out
Hauppauge PVR-150 in another PCI slot
using ivtv version 0.8.2 in Knoppmyth R5E50
PVR is both frontend and backend

Changing channels in live TV is slow (although 4 seconds seems severe). It has to stop recording the old channel to the ringbuffer, start recording a bit of the new channel, then switch over (that's a horribly simplified and possibly incorrect description, but it's something like that).

The way this will be done in the future is changing, but it's unclear whether it will be any faster.

What I usually do is to change a preference (I forget which one, I think it's in General) where channeling up or down only displays the program guide for the channel, and pressing Return changes the channel. That way you can quickly browse program descriptions and only change the channel if something sounds good.

4-5 sec does sound like a long time, though, so maybe something technical is going on as well for you. Have you checked your drive's DMA settings?

http://www.knoppmythwiki.org/index.php?page=HardDrives
http://www.linuxdevcenter.com/pub/a/lin ... dparm.html

Yeah, I saw that wiki entry before, so I have the following n my bootmisc.sh:
# enable DMA
/sbin/hdparm -qd1c1u1m16 /dev/hda
/sbin/hdparm -qd1c1u1m16 /dev/dvd

Also, checking in shell:
root@mythtv:/home/mythtv# hdparm /dev/hda

/dev/hda:
multcount = 16 (on)
IO_support = 1 (32-bit)
unmaskirq = 1 (on)
using_dma = 1 (on)
keepsettings = 0 (off)
readonly = 0 (off)
readahead = 256 (on)
geometry = 16383/255/63, sectors = 120034123776, start = 0


using_dma says 1.

What else could it be?


More hdparm stuff:

root@mythtv:/home/mythtv# hdparm -Tt /dev/hda

/dev/hda:
Timing cached reads: 508 MB in 2.01 seconds = 252.52 MB/sec
c
root@mythtv:/home/mythtv# $ hdparm -Tt /dev/hda
bash: $: command not found
root@mythtv:/home/mythtv# hdparm -Tt /dev/hda

/dev/hda:
Timing cached reads: 508 MB in 2.01 seconds = 252.40 MB/sec
Timing buffered disk reads: 88 MB in 3.03 seconds = 29.06 MB/sec
root@mythtv:/home/mythtv# hdparm -c1 -m16 /dev/hda

/dev/hda:
setting 32-bit IO_support flag to 1
setting multcount to 16
multcount = 16 (on)
IO_support = 1 (32-bit)

_________________
My knoppmyth system:
P-III 850 MHz
256 Mb RAM
Hauppauge PVR-350 connected to tv via tv-out
Hauppauge PVR-150 in another PCI slot
using ivtv version 0.8.2 in Knoppmyth R5E50
PVR is both frontend and backend

It takes my PVR-150 about 2 seconds to change channels when watching live TV. Is anybody able to change more quickly with this tuner?

_________________
MSI K7N2GM2-LSR (Integrated Video)
Athlon XP 2800+
512M RAM
160GB WD
Hauppauge PVR-150

2 seconds is a very good time. 4 seconds is not really all that extreme. Due to the nature of livetv in mythtv this is simply unavoidable. There are some major changes happening to livetv in svn, so this may improve, but no guarantees.

_________________
Have a question search the forum and have a look at the KnoppMythWiki.

Xsecrets

My roommates have a Comcast DVR. It takes a couple seconds to change channels on that as well. Of course that DVR isn't a jukebox, image viewer, video player, DVD player, or multiple game consoles all built in 1 machine. So I guess it all evens out.