It looks like I misspoke - the program now manages to display the SNRM-per-band graphs, and does an initial reading that varies by band, but then the graphs are just straight lines from that point onwards.
There are two ways in which that can happen:
- the values don't change, so the graphs are correct (unlikely but not impossible)
- the pbParams data is only read once, immediately after the start of recording
The second possibility is what happens if none of the optional items under "pbParams" are ticked, but in that case it shouldn't be showing the SNRM per band graphs.
In the next full release, which I'm hoping to put out soon, I've removed those options. On VDSL2 systems the pbParams data will always be read. This should remove the possibility of the second explanation occurring. I can't really see how it's happening now, but I would theorise that DSLstats is misbehaving in some way when a sample is not collected correctly, and perhaps this is a consequence of using a WiFi connection.
Up until last week, the values were always changing in the per-band graphs; when something changed in the overall SNRM graph, there would often be a similar change in at least one of the bands in the per-band graph. It would be strange for there to now be changes in the overall graph, but no corresponding change to per-band.
The WiFi connection was being used back then too. Things do go wrong with it - but I then see a thin line in the speed and overall SNRM graphs, to denote the failure to sample. Looking back, the per-band graphs never seem to show the same thin lines.
In my configuration, the "SNRM per band" item is ticked.
Note: In adding graphs as attachments, I just realised that DSLstats might well be displaying the per-band graphs, but it isn't saving them as part of the automatic snapshots. However, they are saved when I hit the button in the GUI. Lo and behold, the option to auto-save them had turned off on the config screen.
These graphs were being auto-saved before, so whatever change I made (or happened anyway) means this tick has been lost. I've just turned it back on.