Tips

Selective channel loading

Since asammdf 6.1.0 you can use the channels argument to perform a selective channel loading. Only the metadata of channels found in the selection iterable will be preserved after loading the file. This can yield a big speed improvement for loading the file, but also when performing operations with the MDF object (for example select, get, etc.).

required_channels = ["Speed", "Acceleration", "Force"]
mdf = MDF("input.mf4", channels=required_channels)

Data coupling

All the data returned by the MDF methods is decoupled from the raw data found in the original file. For example, if you modify the Signal returned by the get call the changes will not be seen in the raw data. A second get call of the same channel name will once again give you the data found in the original file.

Chunked data access

asammdf optimizes memory usage by processing samples in fragments. The read fragment size was tuned based on experimental measurements and should give a good compromise between execution time and memory usage.

You can further tune the read fragment size using the configure method, to favor execution speed (using larger fragment sizes) or memory usage (using lower fragment sizes).

Optimized methods

The MDF methods (cut, filter, select) are optimized and should be used instead of calling get for several channels.

Each get call will read all channel group raw samples from disk. If you need to extract multiple channels it is strongly advised to use the select method: for each channel group that contains channels submitted for selection, the raw samples will only be read once.

Faster file loading

Skip XML parsing for MDF4 files

MDF4 uses the XML channel comment to define the channel’s display name (this acts as an alias for the channel name). XML parsing is an expensive operation that can have a big impact on the loading performance of measurements with high channel count.

You can use the keyword only argument use_display_names when creating MDF objects to control the XML parsing (default is True). This means that the display names will be available when calling the get method.