[mythtv-users] Some issues with pvr150 cards

[Thomas Fjellstrom]

On Sunday 19 October 2008, Roger Heflin wrote:
> Thomas Fjellstrom wrote:
> > On Friday 17 October 2008, Thomas Fjellstrom wrote:
> >> I'm getting the following messages from the frontend:
> >>
> >> 2008-10-17 16:03:06.468 WriteAudio: buffer underrun
> >> 2008-10-17 16:03:56.564 WriteAudio: buffer underrun
> >> 2008-10-17 16:04:15.065 [mpeg2video @ 0xb6505e88]invalid mb type in P
> >> Frame at 35 29
> >> 2008-10-17 16:04:31.056 [mpeg2video @ 0xb6505e88]00 motion_type at 27 23
> >> 2008-10-17 16:04:31.057 [mpeg2video @ 0xb6505e88]Warning MVs not
> >> available 2008-10-17 16:06:09.643 WriteAudio: buffer underrun
> >> 2008-10-17 16:11:33.834 [mpeg2video @ 0xb6505e88]ac-tex damaged at 39 13
> >> 2008-10-17 16:15:16.846 [mpeg2video @ 0xb6505e88]ac-tex damaged at 44 7
> >> 2008-10-17 16:15:16.853 [mpeg2video @ 0xb6505e88]Warning MVs not
> >> available 2008-10-17 16:15:21.133 WriteAudio: buffer underrun
> >> 2008-10-17 16:16:42.918 DPMS Reactivated.
> >> 2008-10-17 16:16:46.524 DPMS Deactivated
> >> 2008-10-17 16:16:54.708 [mpeg2video @ 0xb6505e88]skipped MB in I frame
> >> at 27 9 2008-10-17 16:17:19.801 [mpeg2video @ 0xb6505e88]00 motion_type
> >> at 42 29 2008-10-17 16:17:41.057 [mpeg2video @ 0xb6505e88]invalid cbp at
> >> 29 29 2008-10-17 16:18:55.030 [mpeg2video @ 0xb6505e88]00 motion_type at
> >> 27 24 2008-10-17 16:19:05.336 [mpeg2video @ 0xb6505e88]ac-tex damaged at
> >> 28 5 2008-10-17 16:20:04.395 [mpeg2video @ 0xb6505e88]ac-tex damaged at
> >> 30 16 2008-10-17 16:23:28.316 [mpeg2video @ 0xb6505e88]ac-tex damaged at
> >> 8 29
> >>
> >> It doesn't seem to be causing a lot of issues, but I occasionally get
> >> stutters or audio corruption. These are brand new pvr150 cards I just
> >> got for about $30 each (I love sales). I haven't seen any DMA issues
> >> yet, but they seem to have the right chipset for it. lspci says:
> >>
> >> 00:08.0 Multimedia video controller: Internext Compression Inc iTVC16
> >> (CX23416) MPEG-2 Encoder (rev 01)
> >> 00:0a.0 Multimedia video controller: Internext Compression Inc iTVC16
> >> (CX23416) MPEG-2 Encoder (rev 01)
> >>
> >> I don't see any errors in dmesg, so I think things are generally ok..
> >> But those mpeg errors, warnings and Audio underruns are curious.
> >
> > Anybody at all know what might cause these issues?
>
> Check to make sure you don't have any heavy disk io processes, if a disk
> process is busy enough to make the mythtv process take too long writing
> data then data gets lost because the next bit cannot be grabbed from the
> card fast enough.
>
> The only other choice is there you are having some sort of PCI issue that
> is also resulting in data being lost.
>
> For both check to see if the backend has messages from the recording time
> that indicates issues.

No backend errors or warnings, in either the mythbackend log, or dmesg. The 
frontend is a combined FE/BE box, but its only the slave backend, another 
computer is the master. The live tv storage group is housed on a raid0 stripe 
of two 160G drives on the same machine, and recordings get placed on that same 
filesystem but also overflow to an NFS share on another box which lives on a 
raid5 of 3 320G drives, over a GbE lan (pci card, so it gets about 300mb/s).

I've looked and both cards share irqs with other devices, one shares with a 
usb2 host and the integrated sound, another shares with the network card. I 
can probably manage to get them both onto their own irqs, but its a royal 
pain, lapic is also somewhat unstable on the box, so i keep it disabled.

When watching a live tv broadcast, the front end usually eats up 20-40% cpu on 
its own, and might spike, which could be causing the warnings, though the 
backend process doing the recoding runs at a paltry 1-2% cpu.

>                                   Roger


-- 
Thomas Fjellstrom
tfjellstrom at shaw.ca