On 01/15/2013 07:12 PM, Mauro Carvalho Chehab wrote:
Em Tue, 15 Jan 2013 17:26:17 +0200
Antti Palosaari <crope@xxxxxx> escreveu:
On 01/15/2013 04:49 PM, Antti Palosaari wrote:
I am a little bit lazy to read all those patches, but I assume it is
possible:
* return SNR (CNR) as both dB and linear?
* return signal strength as both dBm and linear?
And what happens when when multiple statistics are queried, but fronted
cannot perform all those?
Lets say SS, SNR, BER, UCB are queried, but only SS and SNR are ready to
be returned, whilst rest are not possible? As I remember DVBv5 API is
broken by design and cannot return error code per request.
OK, I read that patch still. All these are OK as there is SCALE flag
used to inform if there is measurement or not available.
No anymore question about these.
Issues what I still would like to raise now are:
1) How about change unit from dB/10 to dB/100 or even dB/1000, just for
the sure?
I'm OK with that. I doubt that it would be practical, but we have 64
bits for it, so db/1000 will fit.
2) Counter are reset when DELIVERY SYSTEM is set, practically when
tuning attempt is done. There is new callback for that, but no API
command. Functionality is correct for my eyes, is that extra callback
needed?
Not sure. It should be noticed that, at least on ISDB, some sort of
reset may happen, for example if one layer disappears. The global BER
will (with the current code) reflect the lack of the layer, by not summing
up the data from the removed layer.
Perhaps it makes more sense to, instead, add a way for the driver to flag
when a counter reset happened.
3) Post-BER. I don't need it, but is there someone else who thinks there
should be both pre-BER and post-BER? IMHO, just better to leave it out
to keep it simple. In practice both pre-BER and post-BER are running
relatively, lets say if pre-BER shows number 1000 then post-BER shows
only 10. Or pre-BER 600, post-BER 6. Due to that, I don't see much
interest to return it for userspace. Of course someone would like to
know how much inner coder is working and fixing error bits and in that
case both BERs are nice...
I don't see any need for it. In the case of ISDB, I'll likely convert
the post-BER error into per-layer CNR, as it might be useful for one.
I don't have any strong opinion on that though.
4) Returning bit counts as BER and UCB means also driver should start
polling work in order to keep driver internal counters up to date.
Returning BER as rate is cheaper in that mean, as driver could make
decision how often to poll and in which condition (and return values
from cache). Keeping track of total bit counts means continuous polling!
The way it was specified, the bit count/block count is relative to the
same period where bit error/block error count was taken, and are there
to calculate BER and PER.
Eh, then this is functionality is against 2) what I asked about
functionality of the counter reset. You should make decision to increase
counters continuously and reset only given condition (on channel tune as
it is done now) OR leave whole counter reset and increase to
responsibility of the driver.
Do you see conflict here???
My opinion is to remove counter reset callback and leave all to
responsibility of the driver.
Not all frontends allow continuous measurement of BER and PER. In the
case of mb86a20s, BER is currently not continuous. I think that there's
a way to do continuous PER measurement, but I need to double-check
it.
Personally I am going to implement that way it returns those bit counts
from the driver cache. Driver makes decision when to make measurements,
like just after channel is tuned and after that maybe once per minute or so.
regards
Antti
--
http://palosaari.fi/
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
