Get latest timestamp of MF4

[geo4711]

Hi,
I have many MF4 files with bus logging for several CANs. I'm looking for a method to quickly find out start and end time of the measurement. Start of measurement is contained in the MF4 header. But I couldn't find a quick way to retreive the timestamp of the latest event.
Iterating over all busses (mdf.select(...)) to get the latest timestamp per channel takes a long time for large files (e. g. files with 5 to 10 GB). I already saw the parameter record_offset for mdf.select() and tried to set it to -1 (like common slicing in python). But this did not return the latest sample/timestamp.
I'm wondering how CANoe retreives this information within some seconds.
Does anybody have an idea for a quick method with asammdf?

Thanks in advance for any help!

[geo4711]

I finally found a solution:
Iterate over all channel groups and select the latest record only (and then find the max value of all of them).

def _get_timestamp_of_last_sample(self, mdf: asammdf.MDF, group_idx: int) -> float:
    """Return the timestamp of the last sample of the given group."""
    group = mdf._mdf.groups[group_idx]
    sample_cnt = group.channel_group.cycles_nr
    last_sig_record = mdf.select(
        channels=[(None, group_idx, 0)],
        record_offset=sample_cnt-1,
        record_count=1,
    )
    last_ts = last_sig_record[0].timestamps[0]
    return last_ts

with asammdf.MDF(name=self.filepath, process_bus_logging=False) as mdf_file:
    duration_s = max([self._get_timestamp_of_last_sample(mdf_file, group_idx) for group_idx in range(grp_cnt)])

The important thing is to use process_bus_logging=False when creating the MDF instance. By default, this parameter is True. For large bus logging files, this leads to very long loading times of the file (many minutes up to a few hours for files with some GB).