MDF¶
This class acts as a proxy for the MDF3 and MDF4 classes. All attribute access is delegated to the underling file attribute (MDF3 or MDF4 object). See MDF3 and MDF4 for available extra methods.
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class
asammdf.mdf.
MDF
(name=None, load_measured_data=True, compression=False, version='3.20')¶ Unified access to MDF v3 and v4 files.
Parameters: name : string
mdf file name
load_measured_data : bool
load data option; default True
- if True the data group binary data block will be loaded in RAM
- if False the channel data is read from disk on request
compression : bool
compression option for data group binary data block; default False
version : string
mdf file version (‘3.00’, ‘3.10’, ‘3.20’, ‘3.30’, ‘4.00’, ‘4.10’, ‘4.11’); default ‘3.20’
Methods
convert
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convert
(to, compression=False)¶ convert MDF to other versions
Parameters: to : str
new mdf version from (‘3.00’, ‘3.10’, ‘3.20’, ‘3.30’, ‘4.00’, ‘4.10’, ‘4.11’)
compression : bool
enable raw channel data compression for out MDF; default False
Returns: out : MDF
new MDF object
Notes about compression and load_measured_data arguments¶
By default MDF object use no compression and the raw channel data is loaded into RAM. This will give you the best performance from asammdf.
However if you reach the physical memmory limit asammdf gives you two options
- use the compression flag: raw channel data is loaded into RAM but it is compressed. The default compression library is blosc and as a fallback zlib is used (slower). The advange is that you save RAM, but in return you will pay the compression/decompression time penalty in all operations (file open, getting channel data, saving to disk, converting).
- use the load_measured_data flag: raw channel data is not read.
MDF defaults¶
Advantages
- best performance
Disadvantages
- highest RAM usage
Use case
- when data fits inside the system RAM
MDF with compression¶
Advantages
- lower RAM usage than default
- alows saving to disk and appending new data
Disadvantages
- slowest
Use case
- when default data exceeds RAM and you need to append and save
MDF with load_measured_data¶
Advantages
- lowest RAM usage
- faster than compression
Disadvantages
- ReadOnly mode: appending and saving is not possible
Use case
- when default data exceeds RAM and you only want to extract information from the file
Note
See benchmarks for the effects of using the flags.