[mythtv-users] Choppy Playback & prebuffering message

[glen martin]

Scott Petler wrote:
> 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.
>   
Interesting. What does this mean for 'modern' machines with PCI-E cards,
or those with onboard video? Or mine, which has both (onboard video that
can be overridden with a PCI-E16 card)? Is there something magic about
AGP, and I should preferably replace my frontend with a mobo that
supports AGP?

lspci shows my onboard video and network and ide all on the same pci bus.

My own situation is that I can playback analog content fine, but certain
HD streams (again, playback) cause some prebuffering messages as the
play starts up or when inserting onscreen menus or messages (eg. 'I'),
and if I switch aspect ratios ('W'), playback (and frontend) hangs with
incessant prebuffering messages.

The issue seems bandwidth related. The streams for which I have problems
have very high bitrates.  My confusion has been that the cpu isn't
overly taxed, ticking along at perhaps 50% load.  XvMC, realtime, yadda
yadda.
> 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
>   
I tried setpci on my ide, but lspci didn't reflect any change in value.
Nor any particular effect on performance anyway.


test glenm # lspci -t -v
-[0000:00]-+-00.0  nVidia Corporation C51 Host Bridge
           +-00.1  nVidia Corporation C51 Memory Controller 0
           +-00.2  nVidia Corporation C51 Memory Controller 1
           +-00.3  nVidia Corporation C51 Memory Controller 5
           +-00.4  nVidia Corporation C51 Memory Controller 4
           +-00.5  nVidia Corporation C51 Host Bridge
           +-00.6  nVidia Corporation C51 Memory Controller 3
           +-00.7  nVidia Corporation C51 Memory Controller 2
           +-02.0-[0000:01]--
           +-03.0-[0000:02]--
           +-04.0-[0000:03]--
           +-05.0  nVidia Corporation C51PV [GeForce 6150]
           +-09.0  nVidia Corporation MCP51 Host Bridge
           +-0a.0  nVidia Corporation MCP51 LPC Bridge
           +-0a.1  nVidia Corporation MCP51 SMBus
           +-0b.0  nVidia Corporation MCP51 USB Controller
           +-0b.1  nVidia Corporation MCP51 USB Controller
           +-0d.0  nVidia Corporation MCP51 IDE
           +-0e.0  nVidia Corporation MCP51 Serial ATA Controller
           +-0f.0  nVidia Corporation MCP51 Serial ATA Controller
           +-10.0-[0000:04]--+-05.0  VIA Technologies, Inc. IEEE 1394
Host Controller
           |                 +-08.0  Techsan Electronics Co Ltd B2C2
FlexCopII DVB chip / Technisat SkyStar2 DVB card
           |                 \-09.0  Internext Compression Inc iTVC16
(CX23416) MPEG-2 Encoder
           +-10.1  nVidia Corporation MCP51 High Definition Audio
           +-14.0  nVidia Corporation MCP51 Ethernet Controller
           +-18.0  Advanced Micro Devices [AMD] K8 [Athlon64/Opteron]
HyperTransport Technology Configuration
           +-18.1  Advanced Micro Devices [AMD] K8 [Athlon64/Opteron]
Address Map
           +-18.2  Advanced Micro Devices [AMD] K8 [Athlon64/Opteron]
DRAM Controller
           \-18.3  Advanced Micro Devices [AMD] K8 [Athlon64/Opteron]
Miscellaneous Control

test glenm # lspci -vv -s 0000:05.0
00:05.0 VGA compatible controller: nVidia Corporation C51PV [GeForce
6150] (rev a2) (prog-if 00 [VGA])
        Subsystem: ASUSTeK Computer Inc. Unknown device 81cd
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop-
ParErr- Stepping- SERR- FastB2B-
        Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort-
<TAbort- <MAbort- >SERR- <PERR-
        Latency: 0
        Interrupt: pin A routed to IRQ 20
        Region 0: Memory at fd000000 (32-bit, non-prefetchable) [size=16M]
        Region 1: Memory at d0000000 (64-bit, prefetchable) [size=256M]
        Region 3: Memory at fc000000 (64-bit, non-prefetchable) [size=16M]
        [virtual] Expansion ROM at febe0000 [disabled] [size=128K]
        Capabilities: [48] Power Management version 2
                Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA
PME(D0-,D1-,D2-,D3hot-,D3cold-)
                Status: D0 PME-Enable- DSel=0 DScale=0 PME-
        Capabilities: [50] Message Signalled Interrupts: 64bit+
Queue=0/0 Enable-
                Address: 0000000000000000  Data: 0000

test glenm # lspci -vv -s 0000:0d.0
00:0d.0 IDE interface: nVidia Corporation MCP51 IDE (rev a1) (prog-if 8a
[Master SecP PriP])
        Subsystem: ASUSTeK Computer Inc. Unknown device 81bc
        Control: I/O+ Mem- BusMaster+ SpecCycle- MemWINV- VGASnoop-
ParErr- Stepping- SERR- FastB2B-
        Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort-
<TAbort- <MAbort- >SERR- <PERR-
        Latency: 0 (750ns min, 250ns max)
        Region 4: I/O ports at ffa0 [size=16]
        Capabilities: [44] Power Management version 2
                Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA
PME(D0-,D1-,D2-,D3hot-,D3cold-)
                Status: D0 PME-Enable- DSel=0 DScale=0 PME-

test glenm # lspci -vv -s 0000:10.1
00:10.1 Audio device: nVidia Corporation MCP51 High Definition Audio
(rev a2)
        Subsystem: nVidia Corporation Unknown device cb84
        Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop-
ParErr- Stepping- SERR- FastB2B-
        Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort-
<TAbort- <MAbort- >SERR- <PERR-
        Latency: 0 (500ns min, 1250ns max)
        Interrupt: pin B routed to IRQ 19
        Region 0: Memory at febd8000 (32-bit, non-prefetchable) [size=16K]
        Capabilities: [44] Power Management version 2
                Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA
PME(D0-,D1-,D2-,D3hot+,D3cold+)
                Status: D0 PME-Enable- DSel=0 DScale=0 PME-
        Capabilities: [50] Message Signalled Interrupts: 64bit+
Queue=0/0 Enable-
                Address: 0000000000000000  Data: 0000
        Capabilities: [6c] HyperTransport: MSI Mapping

test glenm # lspci -vv -s 0000:14.0
00:14.0 Bridge: nVidia Corporation MCP51 Ethernet Controller (rev a1)
        Subsystem: ASUSTeK Computer Inc. Unknown device 8141
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop-
ParErr- Stepping- SERR- FastB2B-
        Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort-
<TAbort- <MAbort- >SERR- <PERR-
        Latency: 0 (250ns min, 5000ns max)
        Interrupt: pin A routed to IRQ 16
        Region 0: Memory at febd7000 (32-bit, non-prefetchable) [size=4K]
        Region 1: I/O ports at d080 [size=8]
        Capabilities: [44] Power Management version 2
                Flags: PMEClk- DSI- D1+ D2+ AuxCurrent=0mA
PME(D0+,D1+,D2+,D3hot+,D3cold+)
                Status: D0 PME-Enable+ DSel=0 DScale=0 PME-