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PostPosted: Thu May 17, 2007 5:53 pm 
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Location: Arlington, MA
I'd also keep an eye on the USB networking dongle. USB has a relatively high CPU overhead just because of the way it works. I've noticed this with USB storage devices in the past which use a lot of CPU compared to IDE, SATA or Firewire drives.


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PostPosted: Sun May 20, 2007 4:22 pm 
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Unfortunately my most recent experiments show that the video stutter problems are back when using R5F1, the strange thing is that this stutter occurs when there is no OSD. Also, the CPU% is well below 100%. Maybe I was a little premature when reporting earlier how R5F1 fixed the video stutter OSD problem.

Note, since the earlier reports to this thread I have updated the Nvidia driver to 9755, so maybe the newer driver is not working as well as the older
one which comes with R5F1?


The following is common to all the following setups, unless noted otherwise:

Both SD (PVR-500) + HD (Airstar) cards installed and set up
Using ethernet only (no wireless connection)

KnoppMyth R5F1 installed on SATA drive
Nvidia 9755 driver
UseEvents True (xorg.conf)

<EDIT> Note, the rest of the xorg.conf is what came with the original R5F1 install.

MythTv playback settings:

Enable OpenGL vertical sync for timing – checked
Enable realtime priority threads - checked
Extra audio buffering - checked


Setup #1
========
Bob (2x)
Libmpeg2

Observation: Video stutter, even when OSD is absent. Audio is ok.
Results from top:

top - 14:16:03 up 2:55, 2 users, load average: 1.52, 1.50, 1.35
Tasks: 95 total, 3 running, 92 sleeping, 0 stopped, 0 zombie
Cpu(s): 66.3%us, 32.7%sy, 0.0%ni, 0.0%id, 0.0%wa, 1.0%hi, 0.0%si, 0.0%st
Mem: 771952k total, 760472k used, 11480k free, 1312k buffers
Swap: 1164704k total, 62216k used, 1102488k free, 383520k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3555 root 39 0 206m 188m 104m R 60.9 25.0 7:27.75 Xorg
4405 mythtv 0 0 412m 276m 125m S 38.3 36.7 3:18.67 mythfrontend
4021 mythtv 0 0 411m 32m 7792 S 0.7 4.3 0:56.36 mythbackend
1 root 0 0 2040 476 432 S 0.0 0.1 0:00.86 init
2 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Setup #2
========
Box (2x)
standard

Observation: Video stutter, even when OSD is absent. Audio is ok.
Results from top:

top - 14:21:10 up 3:00, 2 users, load average: 2.85, 2.01, 1.59
Tasks: 95 total, 3 running, 92 sleeping, 0 stopped, 0 zombie
Cpu(s): 73.3%us, 25.3%sy, 0.0%ni, 0.0%id, 0.0%wa, 1.0%hi, 0.3%si, 0.0%st
Mem: 771952k total, 763076k used, 8876k free, 1212k buffers
Swap: 1164704k total, 62216k used, 1102488k free, 386148k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
4405 mythtv 0 0 412m 276m 125m S 52.0 36.7 5:06.56 mythfrontend
3555 root 21 0 206m 188m 104m R 47.0 25.0 9:17.07 Xorg
4021 mythtv 0 0 419m 32m 7792 S 0.7 4.3 0:59.29 mythbackend
298 root 0 0 0 0 0 S 0.3 0.0 0:01.11 kswapd0
3714 mythtv 0 0 10960 864 608 S 0.3 0.1 0:00.17 x11vnc
1 root 0 0 2040 476 432 S 0.0 0.1 0:00.86 init
2 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Setup #3
========
One field
standard

Observation: No video stutter but motion is not very smooth. Audio is ok.
Results from top:

top - 14:24:46 up 3:04, 2 users, load average: 1.34, 1.47, 1.46
Tasks: 95 total, 4 running, 91 sleeping, 0 stopped, 0 zombie
Cpu(s): 62.1%us, 11.3%sy, 0.0%ni, 25.2%id, 0.0%wa, 1.0%hi, 0.3%si, 0.0%st
Mem: 771952k total, 762588k used, 9364k free, 1384k buffers
Swap: 1164704k total, 62216k used, 1102488k free, 386068k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
4405 mythtv 0 0 411m 275m 125m R 49.4 36.6 5:40.09 mythfrontend
3555 root 1 0 206m 188m 104m R 23.9 25.0 9:41.45 Xorg
4021 mythtv 0 0 427m 32m 7792 S 1.0 4.3 1:00.29 mythbackend
3189 mysql 0 0 125m 12m 2412 S 0.3 1.7 0:41.06 mysqld
1 root 0 0 2040 476 432 S 0.0 0.1 0:00.86 init
2 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0


Setup #4
========
Linear blend
standard

Observation: No video stutter but motion is not very smooth. Audio is ok.
Results from top:

top - 14:33:32 up 3:12, 2 users, load average: 2.08, 1.87, 1.66
Tasks: 95 total, 3 running, 92 sleeping, 0 stopped, 0 zombie
Cpu(s): 64.8%us, 9.6%sy, 0.0%ni, 23.9%id, 0.0%wa, 1.3%hi, 0.3%si, 0.0%st
Mem: 771952k total, 761108k used, 10844k free, 1084k buffers
Swap: 1164704k total, 68068k used, 1096636k free, 385892k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
4405 mythtv 0 0 411m 271m 121m S 53.6 36.1 9:19.39 mythfrontend
3555 root 0 0 206m 184m 100m R 20.0 24.5 11:23.30 Xorg
4021 mythtv 0 0 436m 33m 7828 S 1.7 4.4 1:05.80 mythbackend
296 root 0 0 0 0 0 S 0.3 0.0 0:00.70 pdflush
3566 mythtv 0 0 7420 4776 4008 S 0.3 0.6 0:00.63 x-window-manage
1 root 0 0 2040 476 432 S 0.0 0.1 0:00.86 init
2 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0


Setup #5
========
Kernel
Standard

Observation: No video stutter, motion a little smoother than linear blend. Audio is ok.
Results from top:

top - 14:35:23 up 3:14, 2 users, load average: 2.08, 1.94, 1.70
Tasks: 95 total, 2 running, 93 sleeping, 0 stopped, 0 zombie
Cpu(s): 70.9%us, 7.9%sy, 0.0%ni, 19.2%id, 0.3%wa, 1.3%hi, 0.3%si, 0.0%st
Mem: 771952k total, 763544k used, 8408k free, 1588k buffers
Swap: 1164704k total, 68068k used, 1096636k free, 388164k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
4405 mythtv 0 0 411m 271m 121m S 60.3 36.1 10:00.60 mythfrontend
3555 root 0 0 206m 184m 100m S 18.6 24.5 11:39.40 Xorg
4021 mythtv 0 0 452m 33m 7828 S 1.3 4.4 1:07.22 mythbackend
298 root 0 0 0 0 0 S 0.3 0.0 0:01.40 kswapd0
1 root 0 0 2040 476 432 S 0.0 0.1 0:00.86 init
2 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0

Setup #6
========
Kernel
Libmpeg2

Observation: No video stutter, fairly smooth, almost as good as XvMC (but XvMC has
Audio problems, see below). Audio is ok
Results from top:

top - 14:42:24 up 3:21, 2 users, load average: 2.29, 2.43, 2.04
Tasks: 95 total, 2 running, 93 sleeping, 0 stopped, 0 zombie
Cpu(s): 65.3%us, 8.3%sy, 0.0%ni, 24.7%id, 0.3%wa, 1.0%hi, 0.3%si, 0.0%st
Mem: 771952k total, 762392k used, 9560k free, 936k buffers
Swap: 1164704k total, 68068k used, 1096636k free, 387600k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
4405 mythtv 0 0 411m 271m 121m S 54.3 36.1 13:26.09 mythfrontend
3555 root 2 0 206m 184m 100m S 19.3 24.5 12:45.69 Xorg
4021 mythtv 0 0 460m 33m 7828 S 1.7 4.4 1:12.23 mythbackend
1 root 0 0 2040 476 432 S 0.0 0.1 0:00.86 init
2 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0

Setup #7
========
Box (2x)
Standard XvMC

Observation: Video very smooth – no stutter. Audio stutters badly.

top - 15:12:23 up 23 min, 1 user, load average: 1.90, 1.63, 1.09
Tasks: 88 total, 2 running, 86 sleeping, 0 stopped, 0 zombie
Cpu(s): 40.8%us, 5.3%sy, 0.0%ni, 52.2%id, 0.0%wa, 1.2%hi, 0.4%si, 0.0%st
Mem: 771952k total, 760372k used, 11580k free, 1440k buffers
Swap: 1164704k total, 48k used, 1164656k free, 419336k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3609 mythtv 0 0 327m 144m 29m S 45.0 19.1 9:38.04 mythfrontend
3420 mythtv 0 0 312m 34m 12m S 2.0 4.6 0:20.34 mythbackend
1 root 0 0 2044 680 580 S 0.0 0.1 0:00.86 init
2 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0


can anyone suggest what would cause video to stutter when the CPU% is well below 100% ?

Kevin


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 Post subject:
PostPosted: Sun May 20, 2007 6:10 pm 
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Posts: 9551
Location: Arlington, MA
In "realtime" applications latency is the key. Even with CPU use under 10%, if the time critcal processes aren't getting their CPU slice when they need it you'll have problems. This is why working DMA is so critical for hard disks, even though they typically have 10 to 20 times the bandwidth needed. Using DMA avoids certain latency problems which can lead to buffer overflows, and timely buffer service (both reading and writing) is absolutely critical in an application like this. No matter what else it's doing the software needs to keep draining input buffers and filling output buffers or you'll have glitches. It can't get distracted or stuck for too long or it'll blow a buffer deadline.

For example, there was a bug in the version of MythTV 0.20-fixes use in R5E50 where heavy DB usage during recording could cause it not to read the MPEG-2 stream from a PVR card quickly enough leading to a buffer overflow. This occured because the same thread which was supposed to be reading the recording buffers was blocked waiting for the DB to finish commiting an update about the current length of the recording.


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 Post subject:
PostPosted: Sun May 20, 2007 6:11 pm 
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Posts: 158
Just noticed this in the Xorg.0.log ..

Quote:
(**) NVIDIA(0): DPMS enabled
(II) Loading extension NV-CONTROL
(WW) NVIDIA(0): Option "UseEvents" is not used


For some reason it is not taking notice of the UseEvents line in my xorg.conf. Better go away and try and fix this,

Kevin


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PostPosted: Sun May 20, 2007 7:03 pm 
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Posts: 158
thanks tjc for the explanation on a real-time system, I understand a little better now.

Before I give up though on using bob, etc I wanted to mention that it looks like my update to Nvidia 9755 driver appears to have been unsuccessful.

From the KM desktop I just went into nvidia-settings and it tells me that my driver is still at 1.0-8776, clearly something didn't work when I did the driver update. This is how I attempted the driver update ..

Exited MythTV
From KM desktop: CTRL-ALT-F1 (to get to a text window)
install-nvidia-debian.sh 1.0-9755 –force

This downloaded the driver from Nvidia, then after short while it brought up the MythTv screen, so I assumed at that point that it had installed the driver ok – unfortunately it appears that something must have gone wrong.

At no point in the install did I see the usual Nvidia screen pop up where it prompts for my input (yes/no).

I am not familiar with using the install-nvidia-debian script in this way, prior to R5F1 I had to do the manual way of downloading the kernel source and using the pkg1.run file.

Also, note that I did NOT do the startx renaming. (At my first attempt at updating the driver on R5F1 I did rename startx but it seemed to get in all sort of a mess and X wouldn’t come up. After that I did a complete auto install of R5F1 and then used the install-nvidia-debian flow above).

Do you know where I went wrong with the driver update?

Thanks,

Kevin


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PostPosted: Sun May 20, 2007 9:22 pm 
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Posts: 158
Found this Wiki article which is for updating the Nvidia drivers on R5F1 ..

http://knoppmythwiki.org/index.php?page ... diaDrivers

Interestingly, it does say to rename 'startx', so I don't know why this gave me problems before. It wouldn't boot X, it was as if it had a bad xorg.conf but I checked and it was unchanged from the original one. Anyway, I will give the flow in that Wiki article a try tomorrow,

Kevin


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 Post subject:
PostPosted: Mon May 21, 2007 12:32 pm 
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Posts: 158
Followed the instructions in that great Wiki article, my driver is now at 9755

Back now to trying the various options for deinterlacing, etc.

Note,
ultimately the screen I will be using this Myth box with is a 42" Panasonic plasma and it only supports interlaced mode, so I may opt to turn off deinterlacing in Myth.

Ultimately I will be getting a progressive screen but that is some way off (probably years away).

Kevin


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PostPosted: Mon May 21, 2007 5:27 pm 
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Posts: 9551
Location: Arlington, MA
bbear wrote:
From the KM desktop I just went into nvidia-settings and it tells me that my driver is still at 1.0-8776, clearly something didn't work when I did the driver update. This is how I attempted the driver update ..

It sounds like you failed to disable the /etc/init.d/install-nvidia-debian script and it reinstalled the "proven" version. ;-)


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PostPosted: Mon May 21, 2007 10:52 pm 
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Posts: 1422
Location: Brisbane, Queensland, Australia
bbear wrote:
Note,
ultimately the screen I will be using this Myth box with is a 42" Panasonic plasma and it only supports interlaced mode, so I may opt to turn off deinterlacing in Myth.


Kevin,

I have my KnoppMyth box connected to a 68CM CRT television and as most people know this is an interlaced device. With deinterlacing turned off I can not watch sport as the picture looks like crap. So although you may want to turn it off, I don't think that will happen, from my experience anyway. :)

_________________
Girkers


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 Post subject:
PostPosted: Tue May 22, 2007 8:13 am 
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bbear wrote:
Note,
ultimately the screen I will be using this Myth box with is a 42" Panasonic plasma and it only supports interlaced mode, so I may opt to turn off deinterlacing in Myth.
Kevin


What kind of panasonic plasma is it?


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PostPosted: Tue May 22, 2007 9:43 am 
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Posts: 158
I have a Panasonic TH-42PX50 which supports 720p and 1080i, but it does not support 1080p (I believe that your TH-42PX60 does).

Actually, like Girkers I am using a CRT TV at the moment (difficult to get time on the pasma as it is constantly being used for our regular TV viewing), it most definitely only supports interlaced signals so I am a little confused as to how I can set up Myth to deinterlace and yet have it display on an interlaced monitor. Does the video card somehow detect that I have an interlaced-only monitor attached and force the GPU to do deinterlacing before sending it out to the monitor?

Kevin


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PostPosted: Tue May 22, 2007 9:59 am 
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Posts: 158
Just found this thread over at gossamer-threads, this interlacing/deinterlacing thing actually looks to be very complex. Also, it looks like when I eventually switch back to using my box with the plasma display I am going to have to do quite a bit of experimenting before I get the display anything like decent.

http://www.gossamer-threads.com/lists/m ... ers/270200

Quote:
The problem with mythtv's playback is that is not consistent with the
timing of how it presents frames/fields to an interlaced display.

Assuming a 60Hz (ntsc) display, it will be expecting the start of a
new frame every other vertical sync, or more strictly, it expects
fields in the order:-

Sync# Frame Field
0 1 top
1 1 bottom
2 2 top
3 2 bottom

What we actually do in software is present a new frame (both fields)
at syncs 0, 2, 4 etc and the video card takes the the right field at
the right time and sends it to the display in an interlaced format.

If everything worked as it should, the display would then pick up this
field order and deinterlace it correctly.

The problem comes when there is a minor blip in playback, or playback
is just settling down after its been started or paused, and opengl
vsync has to 'resync'. Rather than waiting to start a new frame on an
even numbered sync (using the above timings) it gets the next
available one - which might be odd numbered.

Once this happens, the fields are now being presented to the display
out of order and deinterlacing fails badly.

I suspect some tvs' are smarter than others about detecting when the
fields are obviously out of sync and adjusting.


Kevin


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PostPosted: Tue May 22, 2007 12:38 pm 
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bbear wrote:
I have a Panasonic TH-42PX50 which supports 720p and 1080i, but it does not support 1080p (I believe that your TH-42PX60 does).


While my panny does accept a 1080p input, that doesn't mean that what's displayed on the screen has 1080 lines of resolution. The actual resolution for that display is closer to 1280x720, so I have myth outputting at 720p since the tv will process any input down to it's native resolution anyways.


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PostPosted: Tue May 22, 2007 1:47 pm 
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I have heard that my 42" pana has a native resolution of 1024x768, although I can't seem to find it documented anywhere.

Does this mean that the closest match to the native resolution would be achieved if I configured my xorg.xonf to 720p?

I can see that with a 720p setting that there would be less scaling on the horizontal but wouldn't I loose 48 vertical lines?


"720p" is 720 active scan lines by 1280 active horizontal samples,
"1080i" is 1080 active scan lines by 1920 active horizontal samples,

The standard also provides for 1440 and 1280 horizontal sample versions of 1080i although I am not sure what setting '1080i' in xorg.conf actually forces the video card to output, I am assuming that it is 1920x1080

Kevin


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PostPosted: Tue May 22, 2007 10:27 pm 
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Just been checking my playback settings, with the Nvidia 9755 driver now successfully installed I am able to watch HD content with the Bob (2x) deinterlace setting!

Absolutely no stuttering, even with OSD up :D

R5F1, along with the great number of updates/improvements seems to have finally fixed the stuttering video for me.

Now I move on to such trivial things as tweaking the picture quality on the SD channels (hopefully, just need to up the bitrate on my PVR-500).

In the next day or so I will make a point of reporting all my current settings here, in case it is useful for anyone wanting to replicate my setup.

Thanks to Cecil and everyone who worked on bringing out this excellent release to the community.

(For my questions on whether to use a deinterlacer with my plasma screen and whether to use 720p, I will open a new thread of necessary)

Kevin


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