UPDATE: SEE MESSAGE BELOW DATED DEC 18, 2005

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Hardware:
Computer: e-Machines
CPU: Intel Celeron 500 Mhz
RAM: 256 Mb
Harddrive: Samsung 80 Ghz
TV Tuner Card: Hauppauge PVR-350

Network Topography:
Cable Modem --> Router/Gateway --> Hub --> MythTV Box

Cable Modem: Motorola Surfboard 5120
Router/Gateway: Axentra Net-Box H-70
Hub: NetGear 8 port Model DS108

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Hi All,

I have been playing around with KnoppMyth for a few months now. I purchased a Hauppauge PVR 350, 80 Gigabyte 7200 rpm hard disk and borrowed an E-Machines (500 Mhz Intel CPU, 256 Mb RAM).

With the help of this forum I have been able to successful display video to a TV, view the TV guide, and record TV shows.

The only problem is that video is that video is quite smooth when watching live TV. However, after a day or so, the video becomes choppy when watching live TV or viewing a recording.

Why is watching live TV okay at first, then becomes choppy?

Is it due to the slow CPU speed and low amount of RAM?

Please confirm that the choppy video is likely due to an under-powered system, or suggest what else might cause choppy video.

The reason I am asking is because if it is likely to be due to lack of system power, then I will go ahead and purchase the components for a more powerful system (2 Ghz CPU, 1024 Mb RAM, etc.).

Thanks in advance for any input provided.

Dr. Hood

SSH in and from a command line run top and see what your cpu usage is.

search for hdparm commands to check you disk throuput

If it is not choppy at the beginning it should not get choppy unless something else is running.

Are you using the nvidia drivers

Thanks for the advice, it is much appreciated.

I will check out the CPU usage. I don't know the linux command, but will look it up. Never SSH before, but now is a good time to learn. Will get back tonight.

If you are ssh'ing from a windows box download a free program called putty

once you log in use the command "top" (No Quotes)

That will show your cpu usage

If you're using a Mac (OSX) SSH is ready to go, via a terminal session. Just do a

SSH -l root password

from terminal and you'll get right in. Be aware though .. if you do this (again, with a Mac) and you rebuild the myth system, and the myth system grabs the same ip, the key to the Linux box will change and you'll be denied access. You have to edit a file on the Mac (forget which one, it's a text file) to clear out the information for that IP to get in again.

Hope I didn't confuse the issue - just figured this out the other day.

Thank you for all the replies.

I did the following ssh command from a client workstation running linux....



The following output was returned....



Based on this output, the cpu usage for users and system tasks is only 6%.

Is there another command to use to monitor system resources through ssh?

Any help will be appreciated.

Dr. Hood

Please note: I tried to use the 'top' and 'iostat' commands, but these do not work with the ssh command I am using.

Hi Dr. Hood,

I also use an e-machine, it is 1.3 gig with 384meg, pvr-350 and works fine. (00:23:28 up 54 days, 10:24, 4 users) Don't dispair as I have also run on an IBM 350 PII, 256mem, Rage TNT video, pvr-150 and works good.

Which version of KnoppMyth are you running? I use A16 on my e-machine (haven't gotten around to upgrading) and used A22 & A26 in the IBM.

I have also ran A22 & A26 on an ASRock 1.5gig, 512mem, FX5200, hd3000 and can watch ota hi def with only a little jaggies when lots of motion. mobo has physical issues so I do not recommend it, have to bend things to be able to plug in cards.

The disturbance in play after a few days is sort of strange behavior. Suspect that you have a few recordings and could be trying to do stuff in the background like commflaging. That would take more than what is available for cpu and probably bus sharing to keep the buffer filled. Try turning the flagging off. Also at that 500mhz, you may need to set the eye candy in the music to the #2 settings to reduce cpu load when playing tunes. Important item is to ensure your cache size in mythtv-setup is 1 gig smaller that as reported by df -h

If you have a second computer and both are on the network, it is handy to be able to remote log in and do things at the command line interface (cli)

Hope that is of assistance, other wise try again
Mike

Thanks Mike,

I am using KnoppMythR5A16.

I did as you kindly suggested and made sure that commercial flagging is turned off.

I also set the cach size in mythtv-setup to 5 gig (df -h reports cache is 6).

Unfortunately, studdering continues on viewing liveTV.

Again, I am not sure if this is due to an underpowered machine or if this is a configuration issue. I hate to spend the money on faster components only to find the same problem.

Any additional suggestion will be greatly appreciated.

Dr. Hood

P.S. I also checked and verified that DMA is enabled on the hard drive.

UPDATE DECEMBER 16, 2005 - STOP THE PRESS: I rebooted the machine after I made the changes that Mike suggested and after several hours of playing liveTV, there is no choppyness. I will monitor the TV for the next 24 hours and report if it indeed has gone away.

Thanks Mike!

I just successfully recorded a video with no choppiness or pixelation. This recording was done during the night when our primary television was not being used (mythTV is connected to a very small TV for testing purposes).

Could it be that the choppy video is due to 2 TV's running at the same time?

The choppy video symptom is the following:

(1) On a fresh reboot of MythTV - watching live TV is good, no choppy video.

(2) After some time has passed (actually not measured it), live TV becomes choppy (audio is fine).

I made certain that the cache is 1 Gig less than the cache reported by 'df -h'. I also deleted log files in /var/log/ and there is 1 Gig of free space in /dev/hda1.

Again, I am running MythTV on a low spec system (500 Mhz, 256 Mb RAM).

Anybody have any thoughts on the possibility of choppyness due to interference from another TV?

Dr. Hood

UPDATE: I GOT CHOPPY VIDEO WHEN WATCHING LIVE TV AND THE PRIMARY TV WAS NOT RUNNING. SO, THE REASON FOR CHOPPY VIDEO IS DUE TO SOME OTHER FACTOR. STILL SEARCHING FOR CONFIRMATION THAT THE CAUSE OF CHOPPY VIDEO IS DUE TO UNDER POWERED SYSTEM SPECS.

I solved the choppy video problem and the fix is pretty easy.

After a lot of searching of these forums, I came across this thread that gave me the clues to fix the choppy video

Brand new R5A22 install, Live TV for 5 hours -> CRASH!

The steps that eliminated the choppy video are the following:

(1) Exit out of the MythTV front-end

(2) Start a console session and type


(3) At the first string, select General and press the Enter key on the keyboard

(4) Click the Next button twice

(5) You should be at the Global Backend Setup screen. The second line from the top should be VBI fomat: and (if like mine) is defaulted to NTSC Closed Caption. Change the VBI format option to None

(6) Click on Next 5 times

(7) Click on Finish

That's it!!

No more choppy video for me. I hope this helps others.

P.S. I also turned off commercial flagging.

Dr. Hood

Hi Dr. Hood,

Thanks for the feedback. That has never been an issue for me and thinking back, I never enable it because it doesn't work yet.

Enjoy!
Mike

Great tip and great use of keeping the thread current throughout the posts - you don't feel like you're reading 'old news' with all your little update blurbs. I like it .. going to start doing that myself.

Holy crap I can't wait to get home from work to test this out. I've been having this problem for the last 9 months. I thought it was an IRQ problem, and was about to buy new hardware or something. Crossing my fingers that my MythTV woes will go away. I've never had a Linux system hard lock up so often as I have had this Mythbox lock up I'm excited to get it stable hopefully.

Does anyone know what it is about the closed captioning setup that breaks everything? More to the point, why it waits an undisclosed amount of time to start breaking?

Interesting.... My M/SBE have been rock solid. More feedback on this would be appreciated. This can be set to none by default.

_________________
cesman

When the source is open, the possibilities are endless!

No luck. My VBI setting was already None. After a while the video starts to get messed up. Audio is correct, but every couple of seconds video chops. Also occasionally ( and only when watching a broken recording ) the screen will go to all vertical bars (like the first line of video is being repeated down the entire screen) and lock the system. The only thing that fixes this problem is a cold boot. Rebooting does not help, nor does reloading the firmware. It seems quite random how long the box will go without messing up. Recently it has gone for almost a week, coincidentally when the network was not working, so I was thinking maybe it was some kind of irq conflict. Any advice would be appreciated, I'm glad I'm not the only one who is experiencing this. I do have commercial flagging turned on BTW, but if thats whats causing it, then why doesn't it cause it immediately? Why would it record correctly and flag commercials properly, only to chop later. Also without commercial flagging I may as well have a tivo.