Stream two acquired channels to binary

[Brad10]

I appologize if this is incredibly straightforward, but I seem to be at a dead end. My goal is simple. I want to use Labview to collect two channels of acoustic data (sampling at 50k per channel)  from an NI DAQ card. I want to stream these two channels to binary files (either one file containing both channels, or one file per channel). I then wish to be able to use a separate vi to open these files and convert the data to .wav (or anything really; .wav seems appropriate for acoustic data).

My trouble is that the 'write waveform to file' tends to create very large files that cause memory issues when opening. 

I have tried several variations of using Write to Binary and Read from Binary that have resulted in very mixed up data. 

Any help would be much appreciated. 

[jeanlucpicard · Accepted solution]

what about using tdms files as the intermediate binary? they are standardized, so you don't need to create parser vi-s and have quite good performance

The NI TDMS File Format

[Bob_Schor]

I'm not sure why you are having a problem.  As I understand it, you are sampling 2 channels at 50 KSamples/sec.  You should be able to write pairs of numbers (I'm assuming you are working with a 16-bit A/D, so that's a rate of 200KB/sec -- you should be able to keep up this rate for a long time (unless you are using a 1.44MB floppy).  To achieve reasonable data rates, buffer your data (i.e. send 1000 points at a time instead of 1 at a time) and use something like the Producer (A/D converter)/Consumer (Disk I/O) pattern.

BS

[crossrulz · Accepted solution]

I also highly suggest using TDMS.  And if you are using DAQmx (which you should), there is a DAQmx Configure Logging VI.  Use this VI to have your DAQmx task streamed straight to a TDMS file.  You don't have to do anything else with the data or file.  That is by far the simplest solution.

[Brad10]

Thank you all; I don't know what was wrong with the binary; but I dropped TDMS in its place and the whole thing works beautifully. Thanks!