Different sample values when using asammdf 6.x vs 7.x

[alex-ruehe]

Python version

python=3.10.6 (main, Aug 11 2022, 13:49:25) [Clang 13.1.6 (clang-1316.0.21.2.5)]

os=macOS-12.5.1-x86_64-i386-64bit

numpy=1.23.2
asammdf=7.1.1 / asammdf=6.2.0

Code

MDF version

3.10

Code snippet

from asammdf import MDF
fn = "signals.mdf"
mdf = MDF(fn)
print(mdf.get(X).samples)

Traceback

None

Description

We recently switched from asammdf 6.2.0 to 7.1.1 and some of our analysts reported problems when running their code:

1. Read MDF file (version 3.10, generated using G.i.N. toolchain) with asammdf 6.2.0 in Python 3.10

2. print samples of channel X

3. samples are correct (([-40. -40. 29.75 ... 31.25 31.25 31.25]))

4. Read same MDF file with asammdf 7.1.1 in Python 3.10

5. print samples of channel X again

6. samples are not correct ([-40. -40. -39.25 ... -39.25 -39.25 -39.25])

This behaviour does not apply to all channels, so far we could not detect a system behind which channels are affected, but we're looking into that.

We started debugging the asammdf source code and ended up in the mdf_v3.py:get function when the channel values are extracted. This part looks like it changed significantly between 6.x.x and 7.x.x.

We tried to just export one single channel into a new MDF file using the GUI (v6.2.0), but if we do this, the samples in this file are correct extracted in both versions. If we use a 7.x.x version of the GUI the extracted samples are incorrect.

[danielhrisca]

It would be easiest if you send a file for analysis (email in the profile page)

[alex-ruehe]

I will see what I can do on Monday, thanks!

[danielhrisca]

@r-xela thank you for the demo file. Please try the development branch code

[alex-ruehe]

@danielhrisca We tested some channels where we found the issue and it looks like it works now!