[vdr] Re: Ring buffer overflows - system too slow?

[Oliver Endriss <o.endriss@gmx.de>]

Wolfgang Fritz wrote:
> I am running VDR with one Nexus-s rev. 2.2 on a 133 MHz/64MB Pentium
> board with Kernel 2.4.20, newest CVS DVB driver and VDR-1.1.21
>
> If I compile VDR with
>
> #define DO_REC_AND_PLAY_ON_PRIMARY_DEVICE 1
> #define DO_MULTIPLE_RECORDINGS 1
>
> I get lots of "ring buffer overflow" messages while recording and the
> recording is damaged.
>
> This happens
> - Sometimes during recording alone
> - Often when recording while replaying another recording or time
> shift
>
> The strange thing is that sometimes a recording + replay is working
> stable with system load at abt 0.6 to 0.8 and on the next try I get
> the ringbuffer messages and the load rises to 1.2 - 1.5.

It depends on the data rate. For example, if the picture contents 
change rapidly, there is more data to be processed and your machine 
reaches its limit.

> Maybe my system is simply to slow? Has anyone out there a single
> DVB-s setup working reliable with DO_REC_AND_PLAY_ON_PRIMARY_DEVICE
> etc. enabled and if so, on what kind of hardware?

I'm using a PI-233 MHz. During recording, system load varies between 
20 and 100%. Probably this is too much for your P-133.

I think the situation could be improved if parts of the driver 
would be optimized. In time-shift mode the driver wastes lots of CPU 
cycles busy-waiting in wait_for_debi_done(). If this could be changed,
CPU utilization of the driver would be reduced significantly. 

I wish I had more time to work on this. Because there is no documentation
about the driver-arm-communication this is a quite time-consuming task.

Oliver


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