[linux-dvb] FE_READ_BER and FE_READ_UNCORRECTABLE might be swapped for stv0299

Johannes Stezenbach js at linuxtv.org
Sun Aug 14 13:54:07 CEST 2005


On Sat, Aug 13, 2005 Jeremy Hall wrote:
> Is it possible that FE_READ_BER and FE_READ_UNCORRECTABLE might be swapped 
> for stv0299?
> 
> I'm looking at a transport and the uncorrectable blocks are much higher 
> than the BER blocks.  Is this expected behavior?

By definition BER is an error rate (i.e. number of wrong bits
per 10^x received bits, with x typically = 12..18), which
UNC is an absolute count of errored TS packets since
the last call to FE_READ_UNCORRECTABLE.

However, the stv0299 cannot measure both, so what Andrew
implemented is rather crude: switch the error mode and
block 100msec and return an absolute count in both cases.

Which means that the number of wrong bits per 100msec
before error correction should be higher than the
number of errored packets per 100msec after error correction.

Maybe Andrew can comment on this, I would guess that switching
the error mode doesn't reset the error counter, and a dummy
read needs to be added.


Johannes




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