Linux media HTPC video playback CPU utilization and optimization

This subject comes up often, but I've run into a 1080i LiveTV (Watch TV) playback issue on another MythBuntu 8.04 build.

It has a 7300GS PCIe, Biostar Nvidia chipset S939 mobo, 1GB DDR3200 and a single core A64 3500.

At first I thought the issue was the QAM demodulation with the Kworld 115 card, but I noticed the image in "Watch TV" only broke up and hesitated/jerked on 1080i channels- no issue with 720p channels.

I tried using the "Slim" setting (vs CPU+) in the Front End Setup->TV->Playback options, and it helped on the 1080i channels, but the System Monitor would still peg at 100% and jerk the image occasionally.

Since others here have stated good ATSC playback with as little as a Duron 1600, I thought an A64 3500 would be home free for 1080i ATSC/QAM.

Any other ideas for settings or tweaks?

...I may have to put an X2 in there

Yes, from EnvyNG

Any more hints on the "secret sauce" to reduce CPU utilization on live ATSC 1080i on Mythbuntu?

Where are the deinterlacing parameters in Myth?

I think the Mythbuntu guys need to do a better job of auto-setting the CPU intensive parameters related to video processing during the install wizard, checking the CPU and GPU/video driver for performance and then setting some video parameters for you.

Unfortunately, socket 939 X2's are much harder to find. Anyone got a lead for retail boxed new S939 X2's? There's always ebay....

I assume the numbers on the rules are priorities?

THe first 3 rules were for 720p or below, and the last two appeared the same for res >0,0 -> xvMC, so I assume 1920x1080 would be covered by rules 4 and 5 since 1-3 were for 1280x720 or less.

I changed rules 4 and 5 to explicitly cover >1280x720, used standard xvMC and Bob deint- no change on 1080i channels

I still get flashes of small sqares every other second or so- different from the breakup you see with low signal strength.

I found this at mythtv.org

http://www.mythtv.org/docs/mythtv-HOWTO-3.html

"To playback HDTV content, plan on a powerful CPU. "How powerful?" depends on a number of factors, such as the capture resolution, whether the video is progressive or interlaced, and whether your display card has hardware-assist support for Linux.

The Simple Answer: Once you are in the 3.2 Ghz P4-class of CPU you should have no issues with viewing HDTV.

The Complicated Answer:

For 720p content (1280x720), a 2.4GHz P4 should be sufficient.

For 1920x1080i->1920x1080p with the better deinterlacing methods done in real time a 2.4GHz CPU is taxed, but should work if you use "Bob and Weave" deinterlacing, or if you have an NVIDIA card with MPEG-2 hardware acceleration. If you enable the hardware acceleration, you may be able to use a 1.8GHz processor."

Does XvMC being enabled with the current proprietary Nvidia driver installed guarantee MPEG2 GPU assist on FX5xxx, 6xxx and 7xxx series Nvidia cards?

I was also suspecting the DMA setting on the hard drive assigned to Myth recording- what is the simplest way to check/verify DMA setting on a hard disk?

BINGO!

You win the thread prize!

The SECRET SAUCE for this thread is:

\tOption \t\t"UseEvents"\t"True"

However, I added the line to *Screen* section of xorg.conf, NOT the Device section per:
http://www.debianhelp.org/node/3146

Section "Screen"
\tIdentifier\t"Default Screen"
\tMonitor\t\t"Configured Monitor"
\tDevice\t\t"Configured Video Device"
\tOption\t\t"AddARGBGLXVisuals"\t"True"
\tOption \t\t"UseEvents"\t"True"
\tDefaultdepth\t24
EndSection

I attached my xorg.conf file.

Another link says to put it in the Devices section, but I didn't try it-
http://www.redhatmagazine.com/2007/1...vidias-driver/

I don't know if there's any difference between the Devices and Screen sections for the UseEvents parameter

1080i channels are now butter smooth, using ~70% CPU +/- 5%, and about 50% with 720p channels.

Why EnvyNG and/or the Nvidia driver doesn't add this important line to the xorg.conf file is unknown...

 

xorgConf.txt 1.3564453125k . file

I had used hdparm before- should have googled, but thanks. It returned:

sudo hdparm -i /dev/sda1

/dev/sda1:

Model=WDC WD800JB-00FMA0 , FwRev=13.03G13, SerialNo=WD-WMAJ91071310
Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq }
RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=58
BuffType=unknown, BuffSize=8192kB, MaxMultSect=16, MultSect=?16?
CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=156301488
IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
PIO modes: pio0 pio3 pio4
DMA modes: mdma0 mdma1 mdma2
UDMA modes: udma0 udma1 udma2 udma3 udma4 *udma5
AdvancedPM=no WriteCache=enabled
Drive conforms to: Unspecified: ATA/ATAPI-1,2,3,4,5,6

* signifies the current active mode


So I am good to go re: dma on the recording hard drive, which appears to be set to udma5.

The hard drive had nothing to do with the hesitating 1080i and flashes of small squares, apparently.

And this is with the Myth Back End record directories set to /home/$user on the same drive as / (i.e using a single hard disk, the WDC WD800JB above)

I intend to add a separate 200G drive dedicated to video recording anyways...

As always, the AVS braintrust saves the day

I deleted the Kworld 115 in the Myth backend, re-added it, then did a fresh channel scan on WoW basic analog cable to pick up the unencrypted OTA stations sent as QAM-256 digital.

After removing the music channels that don't work in the Front End, I exited, did a mythfilldatabase from schedulesdirect, then ran the Front End again.

I tested 1080i on NBC-HD (Today show) this morning- the CPU usage varied a consistent 60%-70%, rarely higher. This is with XVMC, bob deint, and the UseEvents=True option. Looks awesome, no hiccups for 1080i.

Based on these results, I feel comfortable with the single core A64 3500+ (2.2Ghz). I think you'd be good down to an A64 3200 or 3000, but wouldn't go lower, as you want some headroom. Nice to know a single core can still do OTA MPEG2 HD 1080i.

If someone tests a single core using a 64 bit Linux and Myth, please report CPU usage.

To clarify for others, I *don't* recommend using anything less than an X2 4600-5000 for x264 1080p, x2 6000 even better.

This thread discussed the low end CPU "hard stop" for MPEG2 1080i from over the air or cable sources.

CPU requirements for video playback depends on both resolution (480p, 540p, 720p, 1080i, 1080p) and codec (MPEG2 vs x/h264 vs VC1 vs Xvid). A lot of people only need SD with any codec, and occasional HD MPEG2 from over the air sources only, which dramatically reduces CPU requirements. Others may want these plus x/h264 720p only, which also needs significantly less CPU than 1080p x/h264. I don't know exactly where the CPU low end "hard stop" is for 720p x264- I suspect any X2 would do it fine, plus the higher speed single cores (A64 4000-4600?)

I meant the resolution of the source (mkv file, avi file, feed from antenna, etc), not the resolution the video card is set to. Sorry for the confusion.

Thanks for the tweak settings, though. Your results at 2Ghz with ATSC MPEG2 appear to agree with mine.

Bump to keep this active- good info for noobs or a new build.

Bump- prolly should be sticky...

My CPU usage numbers are all *total* CPU- not per process.

Based on total CPU, it appears our numbers agree.

I think the safest route in the short run on Linux is to go with the most CPU cores and most CPU Ghz you can afford, as Linux currently needs to do more in software vs the proprietary hardware acceleration on Windows. The money you save on more expensive GPU's can go into more CPU cores/GHz, which helps your overall system more anyways.

Until AMD/ATI and Nvidia get XvBA and VDPAU up and running to enable hardware acceleration of video decoding in their Linux drivers with common media apps in Linux, we need to protect ourselves with ample cores and GHz to cover for CPU utilization for software decoding/post processing- no big deal, as Moore's Law is on our side. Until XvBA and VDPAU are working in an easy fashion (i.e. no special patches/compiling needed) with the mplayers, VLC's, Geexbox's, XBMC's and MythTV's of the world, just use Nvidia FX5xxx, 6xxx or 7xxx GPU's for the time being, which are practically free now. A side benefit for media PC use is that these are easy to find passively cooled- you don't want fans on your GPU.

Besides, software decoding is more flexible in the long run, and long time avsforum members know that the pendulum has swung several times back and forth between hardware and software decoding of video, with the consensus among avsforum members over which is "better/preferred" shifting every few years. At the moment, Linux and Windows are simply "out of sync" on what is preferred