LabVIEW
Display Problem with Time-Frequency Spectra
Solved!
I was just handed a .WAV file containing some utterances, and asked to determine the frequency spectrum so we could order appropriate speakers to play the sounds. Because they are short utterances (a 4-5 second example is below), I decided to use the Short-Time Fourier Transform (STFT) code to create a Time-Frequency Spectrograph. I'd not done this previously, so I installed the Advanced Signal Processing Toolkit, ran some of the Time Frequency Analysis examples, read the Help files, and went to work. My (partly-successful) code snippet is below (the problem isn't the analysis, It's the Display, Dummy):
Spectrogram Query
I read a Sound File, extract the (only) left channel, and run it through the STFT routine. I scale it using the Configure Spectrogram Indicator, specifying to Use dB and Ignore Timestamp (and providing a Reference to the Time-Frequency Spectrogram Indicator, an Intensity Graph, that it produces.
When I first did this, I started with a copy of one of NI's Examples, and got a nice Spectrogram. I started editing NI's code, replacing it with my own and simplifying somewhat (see above), but wiring it to the Indicator that came with the Example (why not?). As you can see, below, I got a nice picture.
Time-Frequency Spectrograms
So far, so good. So I added a second spectrogram (for comparison), but this time I right-clicked the output from the Configure Spectrogram Indicator VI and chose "Create Indicator". This gave me the second plot above (I used the same data here, of course). So what's the problem?
Notice the Amplitude Indicator, the little Rainbow Bar shown to the right of Spectrogram #1, but missing in Spectrogram #2. I've been looking all over for this, and can't figure out where it is. I've compared (by hand) many of the Properties of the two Intensity Graphs (using LabVIEW to examine all of the Z-Scale properties), and haven't found where they differ, but clearly they do.
One other thing is annoying me -- in the Block Diagram, the Label for Spectrogram #1 (the one I "borrowed" from the LabVIEW Example) has a box around it. I may have known at one time how to "box" such a label, but I've forgotten, and can't get rid of the box! [This seems almost too trivial to worry about, but it bugs me ...].
Just so I don't have Bob_Schor yelling at me about not posing Pictures (I'm sure he'd be OK with Snippets), I'll also attach the code, with "Make Current Values Default" (which I hope preserves the Pretty Pictures).
Bob Schor
Re: "boxing" a Label- shift-right click on the background of the label, select color picker, choose Transparent, bang no more box 🙂 The box comes from a white background AFAIK.
@Bob_Schor wrote:
Notice the Amplitude Indicator, the little Rainbow Bar shown to the right of Spectrogram #1, but missing in Spectrogram #2. I've been looking all over for this, and can't figure out where it is. I've compared (by hand) many of the Properties of the two Intensity Graphs (using LabVIEW to examine all of the Z-Scale properties), and haven't found where they differ, but clearly they do.
The Rainbow Bar is there in #2. Customize the control and move the plot you will see it hiding. Seems like a bug.
mcduff
It's more of a "glitch" than a bug 🙂 You can do it without having to customize the control:
Run that 2-3 times and it'll come out of hiding. It's unfortunate you can't select something "behind" something else if they're part of the same "parent". You'd have a similar issue if you hid the label behind the graph.
I don't have that toolkit installed, but I've noticed that frequently when right-clicking and picking "Create indicator" you can have some weirdness where it'll use the format of the indicator on the VI that you clicked on- not always the base type of the VI.
Could the Z axis be hidden in that VI's front panel for some reason? Maybe it's just that specific VI that has an accidentally hidden Z axis. Does the same thing happen with other "Create indicator" VI's that generate spectograms?
