Devin Heitmueller schrieb:
On Fri, Mar 13, 2009 at 6:27 PM, VDR User <user....@gmail.com> wrote:
Just wanted to comment that I'm glad there is a lot of interest in
this. I've heard endless talk & confusion on the user end over the
years as to the accuracy of the values, or in some cases (as with
Genpix adapters for example) where you don't seem to get any useful
information. Of course making it really hard for people who are
trying to aim dishes and the like in the case of dvb-s*.
A quick question about implimenting this though.. What's the most
difficult component?
Hello,
There are basically two "difficult components"
1. Getting everyone to agree on a standard representation for the
field, and how to represent certain error conditions (such as when a
demod doesn't support SNR, or when it cannot return a valid value at a
given time).
Its just straightforward as described in DVB API, chapters
2.2.3 FE READ STATUS
2.2.4 FE READ BER
2.2.5 FE READ SNR
2.2.6 FE READ SIGNAL STRENGTH
2.2.7 FE READ UNCORRECTED BLOCKS
if ioctl suceeds with valid data: 0, if not one of
EBADF no valid file descriptor.
EFAULT error condition
ENOSIGNAL not yet, i have no signal..
ENOSYS not supported by device.
2. Converting all the drivers to the agreed-upon format. For some
drivers this is relatively easy as we have specs available for how the
SNR is represented. For others, the value displayed is entirely
reverse engineered so the current representations are completely
arbitrary.
Devin
Since a lot of frontends have no proper docs, probably providing the
signal strength unit with a second ioctl could make sense here.
a.u. arbitrary units, not exactly known or not perfectly working
dBµV comparable trough all devices, but probably not possible for all
percent technical not understandable, percent relative to what?
Assumes that there is a optimum/hard limit of 100% which is not the case.
Showing values as human readings is on the app side, so hex output in
raw numbers are just fine here. No change needed.
-- Winfried
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
