[mythtv-users] Choppy Playback & prebuffering message
Scott Petler
scottp at sonic.net
Fri Apr 14 18:53:48 UTC 2006
Nate,
After reading more about your particular machine, I think the issue is
even more likely due to
a pci bus bandwidth issue. This is because your video card is PCI
rather than AGP.
Having both the backend and frontend on the same machine is using up
your PCI bandwidth.
I would suggest a system with AGP video to keep your playback path off
of the PCI bus.
If you can't do this then given the specs below, you are going to need
to allow the
devices in the video path more time on the bus to burst their data.
It looks like the disk controller here has a latency of 0, I would up
this to at least 32.
I'm not very familiar with the ICH4, assuming it has a latency timer for
burst transfers:
(as root)
# setpci -s 00:1f.1 latency_timer=20
See if 1) it actually changes the value, 2) it makes any difference and
if not (2) then try a higher value (repeat)
Scott
Nate Crosno wrote:
> Thanks for the info. I wouldn't know where to begin changing
> latencies. It's all on one box, so LAN latency wouldn't be it. I did
> stop by Circuit City last night and pick up an Nvidia FX5200 128MB
> PCI (I don't have AGP). After updating everything to us xvmc the
> problem is better, but still not good enough for actually watching
> anything....even the OTA-SD channels are choppy. I only played with
> it for a minute though and didn't get any CPU numbers yet. Still
> several tweaks I want to try.
>
> Anyway, in case you have an ideas, here is some info (snipped) from
> 'lspci -v'
>
> 00:00.0 Host bridge: Intel Corporation 82845G/GL[Brookdale-G]/GE/PE
> DRAM Controller/Host-Hub Interface (rev 01)
> Flags: bus master, fast devsel, latency 0
> Memory at e8000000 (32-bit, prefetchable) [size=32M]
>
> 00:1d.7 USB Controller: Intel Corporation 82801DB/DBM (ICH4/ICH4-M)
> USB2 EHCI Controller (rev 01) (prog-if 20 [EHCI])
> Flags: bus master, medium devsel, latency 0, IRQ 17
>
> 00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 81)
> (prog-if 00 [Normal decode])
> Flags: bus master, fast devsel, latency 0
> Bus: primary=00, secondary=01, subordinate=01, sec-latency=32
>
> 00:1f.0 ISA bridge: Intel Corporation 82801DB/DBL (ICH4/ICH4-L) LPC
> Interface Bridge (rev 01)
> Flags: bus master, medium devsel, latency 0
>
> 00:1f.1 IDE interface: Intel Corporation 82801DB (ICH4) IDE Controller
> (rev 01) (prog-if 8a [Master SecP PriP])
> Flags: bus master, medium devsel, latency 0, IRQ 16
>
> 00:1f.3 SMBus: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M)
> SMBus Controller (rev 01)
> I/O ports at eda0 [size=32]
>
> 00:1f.5 Multimedia audio controller: Intel Corporation 82801DB/DBL/DBM
> (ICH4/ICH4-L/ICH4-M) AC'97 Audio Controller (rev 01)
> Flags: bus master, medium devsel, latency 0, IRQ 20
>
> 01:04.0 Multimedia video controller: Conexant CX23880/1/2/3 PCI Video
> and Audio Decoder (rev 05)
> Subsystem: ATI Technologies Inc HDTV Wonder
> Flags: bus master, medium devsel, latency 64, IRQ 18
>
> 01:04.1 Multimedia controller: Conexant CX23880/1/2/3 PCI Video and
> Audio Decoder [Audio Port] (rev 05)
> Subsystem: ATI Technologies Inc Unknown device a101
> Flags: bus master, medium devsel, latency 64, IRQ 11
>
> 01:04.2 Multimedia controller: Conexant CX23880/1/2/3 PCI Video and
> Audio Decoder [MPEG Port] (rev 05)
> Subsystem: ATI Technologies Inc Unknown device a101
> Flags: bus master, medium devsel, latency 64, IRQ 18
>
> 01:05.0 VGA compatible controller: nVidia Corporation NV34 [GeForce FX
> 5200] (rev a1) (prog-if 00 [VGA])
> Flags: bus master, 66MHz, medium devsel, latency 248, IRQ 20
> Memory at fd000000 (32-bit, non-prefetchable) [size=16M]
> Memory at f0000000 (32-bit, prefetchable) [size=128M]
> [virtual] Expansion ROM at ea000000 [disabled] [size=128K]
>
>
>
> Scott Petler wrote:
>> Nate,
>>
>> I don't understand the 100% cpu utilization, but I had similar problems with
>> a similar machine that was a frontend only.
>> 1GB
>> 2.6.15.6 kernel
>> 2.53GHz P4 Socket 478
>> Gigabyte 81848P Mobo
>> GeForce 6600 dual dvi w/ dual 21" LCD monitors
>>
>> I tried all of the "priority" methods, realtime module, suid etc;
>> nothing helped.
>> Kept getting the pre-buffering messages. Eventually I used lspci -v to
>> examine
>> the latency numbers for the pci bus. I found that by setting the
>> latency HIGHER
>> on the LAN and SATA(disk) controller, my problems went away.
>>
>> On the frontend machine, my cpu utilization is about 13% when watching
>> live tv.
>> I'm using the svideo input on a pvr150 on my server, and when watching
>> live tv
>> the server is almost idle, since it only has to store the encoded data
>> to disk and then
>> read data from disk and send it out the LAN interface.
>>
>> The backend server machine is a dual opteron 248 w/ 4GB memory 1TB raid
>> 5 w 4 350GB
>> sata disks and 2 10krpm disks for os/swap.
>>
>> Try out the setpci command on your frontend machine to mess with your
>> latencies and see if that helps.
>> Remember the lspci displays latency in decimal, whereas setpci uses hex....
>>
>> Scott
>>
>> Nate Crosno wrote:
>>
>>> Hi All,
>>>
>>> I'm having lots of frustration getting content to play back smoothly.
>>> Sorry for the noob question. I'm sure you pros get this all the time.
>>> I've been building up this myth box for about a couple weeks and cannot
>>> get anywhere close to smooth playback. I can usually sort these things
>>> out on my own, but am loosing my patience. I've been using Linux on and
>>> off since about 1998 and am a web developer by trade. Most of my
>>> experience is with back-end server type setups.
>>>
>>> Here is my hardware:
>>> - Dell Dimension 2400
>>> - Celeron 2.2Ghz
>>> - 756MB RAM
>>> - ATI HDTV Wonder capture card.
>>> - Radeon 7000 PCI 64MB (right now set to 1024x768 @ 60hz, dri and drm
>>> seems to be loading fine according to the Xorg.0.log)
>>> - 160GB Seagate drive UATA 7200RPM (dma enabled)
>>> - On-board Intel audio
>>> - Right now hooked up to a Dell 15" LCD monitor via VGA, but shooting
>>> to hook it up to my Sony 50" LCD rear projection via the DVI port.
>>>
>>> Software:
>>> - Gentoo linux kernel 2.6.15-gentoo-r1 (recompiled several times over
>>> the past couple days to get things working)
>>> - problem happens on both Gnome and blackbox
>>> - latest mythtv build via 'emerge'
>>>
>>>
>>> When trying to view recorded content or watch live TV (either SD or HD)
>>> I get the following:
>>> - Pauses every 1-2 seconds (speeding up, slowing down, etc), this
>>> includes breaks in the sound.
>>> - in the mythfrontend terminal window I see lots of messages about
>>> 'prebuffering pause'
>>> - big pink vertical bar along the right edge of the content (on SD
>>> content)
>>> - if I turn off the sound (set the sound device to something invalid
>>> in myth), then it seems to just play slowly
>>> - while only mythbackend is running and recording HD content 'top'
>>> shows only about 10% CPU usage.
>>> - while trying to watch live tv or recorded content, the CPU gets
>>> maxed out:
>>> 0% idle, 60% mythfrontend, 27% X
>>> 0% swap in use
>>>
>>> I'm hoping something here will catch your collective eye.
>>>
>>> I've tried many of the various settings like aggressive sound buffering
>>> to no avail.
>>>
>>> Thanks a million!
>>> -Nate
>>> _______________________________________________
>>> mythtv-users mailing list
>>> mythtv-users at mythtv.org
>>> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>>>
>>>
>>>
>>>
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