# SpikeGLX FAQ

Topics:

- Why SpikeGLX?
- How to Uninstall
- Side by Side Versions
- Running Two Copies of SpikeGLX
- Data Integrity
  - Graceful Shutdown
  - Crash
- Gauging System Health
- How to Report Bugs
- Memory Leak
- Graphics Problems
  - Fuzzy Text
  - Black Graphics
  - Graphs Flicker
- Remote Desktop
  - Audio Output Tip
  - Audio Output Crash

## Why SpikeGLX?

“What’s the point? Why SpikeGLX vs. the other leading brand?”

1. Strong integration and synchronization. As originally conceived the Imec ‘Neuropixels’ probes recorded lots of neural channels but had very limited auxiliary inputs for accelerometers, physiological readouts, lick responses, door activations and so on. Combining the Imec and Nidq streams vastly expands the aux inputs available in your experiment. Moreover, all of the data are tightly synchronized. You can see them together on screen during an experiment, the output files are synced to within a few samples and the offline File Viewer lets you review all the recorded data in a time-locked way. This helps you see the experiment as an integrated whole.

2. Several options for timer or event-driven control of file writing.

3. Remote control. You can use the MATLAB, Python, C#, C or C++ interfaces over a network connection to: set/get run parameters, start/stop runs and file writing, and retrieve data, all in real time.

## How to Uninstall

“How do I completely remove SpikeGLX from my computer?”

When you download a release of SpikeGLX you get a folder with a name like “Release_v20161101”. Everything SpikeGLX needs to run is in that folder. There are no Registry entries, no DLLs placed into Windows OS folders or any other cookies or crumbs.

To delete it, drag the release folder to the trash.

## Side by Side Versions

“Can I have multiple versions of SpikeGLX on one computer?…Will they interfere with each other?”

Yes, not a problem. Refer to FAQ How to Uninstall to see that each SpikeGLX setup is self-contained. We organize things like this:

    SpikeGLX/               // master folder with all versions
        ...
        Release_v20160703/  // a release folder
        Release_v20160806/  // another
        Release_v20161101/  // and so on
        ...

## Running Two Copies of SpikeGLX

“What happens if I try to run two copies at the same time?”

If you are only doing offline things, like using the File Viewer, there is no problem. You can run as many instances as you want until you run out of RAM. There are only issues if data acquisition hardware is involved.

If you are using NI-DAQ hardware, you have to visit the Configuration dialog in SpikeGLX, check `Enable NI-DAQ` and click `Detect`. The first instance of the app to do that gets ownership of the NI-DAQ hardware and no other instance will be allowed to use it. This prevents accidental conflicts which is a good thing, but it also prevents running multiple NI-based probes on one host computer.

Imec hardware uses a fixed static IP address, and that generally prevents running two setups from one host. There is a workaround developed <here> that I haven’t tried; please don’t ask me for any details about that.

Another related question is whether one can run two copies of SpikeGLX on one computer, each running a command server that can be individually addressed from MATLAB. Yes, it works fine. In each copy of SpikeGLX, use `Options/Command Server Settings...` to assign the computer’s network IP address, but give each application its own port number. From MATLAB, connect using `SpikeGL( IP-address, port )`.

## Data Integrity

“My run quit unexpectedly, are my data likely to be corrupt or garbage?”

### Graceful Shutdown

SpikeGLX monitors a number of health and performance metrics during a data taking run. If there are signs of pending trouble it will initiate a graceful shutdown of the run before a catastrophic failure occurs. It closes open data files and then stops the data acquisition. Messages in the Console window’s log will describe the specific problem encountered and the fact that the run was stopped. Your data files are intact because we close them before corruption happens.

### Crash

A graceful shutdown, described above, is not a “crash”. Software engineers reserve the term “crash” for a completely pathological and unexpected event that is so bad, the operating system must step in and terminate the application with extreme prejudice before harm is done to other programs or to the OS itself.

What are the signs of a crash? When an event like this happens, there will usually be a Windows OS dialog box on the screen with a cryptic message about quitting unexpectedly. Often, since Windows 7, the screen has a peculiar milky appearance after a crash. A really severe crash ends in the blue screen of death.

Crashes are usually the consequence of software bugs (bad practice) and these mistakes are fixed over time as they’re uncovered. If a crash happens while running SpikeGLX (unlikely), you’re still in pretty good shape because the data files will be intact up to the moment just before the crash. The crash itself will be very swift, so only the last few data points in the files may be in question.

You can edit and recover files even after a crash by doing two things:

1. Right-click on the `bin` file in Windows File Explorer and select `Properties` to get the size in bytes (not size on disk). This needs to be an integral number of whole timepoints. A timepoint has size: numChannels x bytesPerChannel, that is: meta-item `nSavedChans` x 2. If the actual file size does not match, trim the excess using a binary file editor or using a Linux editing tool like `head` to remove the excess, like this: `head -c [number of bytes to keep] [my bin filename] > [my new filename.bin]`

2. If a crash occurs the final write to the meta file may not happen, so you’ll need to reconstruct three key meta items. First, set `fileSizeBytes=nn`, where, nn is the same size as discussed in step (1). Second, set `fileTimeSecs=ss`, the span of the file in seconds, calculated like this:

        ss = fileSizeBytes / xxSampleRate / nSavedChans / 2,
        where, xxSampleRate is the niSampleRate or imSampleRate
        recorded in the same metafile.

Lastly, if the meta file is missing checksum item `fileSHA1` then simply add an entry setting it to zero: `fileSHA1=0`. This will allow you to open the file with the SpikeGLX File Viewer.

## Gauging System Health

“What can I observe about SpikeGLX to look for performance issues?”

- Open the Windows Task Manager and watch network performance. The usage graph runs at something like 15.3% to 15.5% for Imec data transfer and is pretty steady. Steady is good, while varying throughput means the system is struggling.

- The main Console window status bar, when writing files, displays the current file buffer fill percentages (imec%,nidq%), which should remain below 5%, and it shows the disk write rate which should be around 1500+ MB/s. The write rate could be much higher for SSD drives. If these are varying the system is struggling.

SpikeGLX doesn’t write data files with gaps. Rather, if any resources are choked beyond a monitored threshold the run is stopped gracefully. There are some specific monitoring messages that may appear in the text of the Console window…

- If data are not being pulled from the hardware fast enough you’ll start to see messages like this: “IMEC FIFOQFill% value, …” These messages are triggered if the fill % exceeds 5%. The run is automatically stopped at 95%. No messages are written if the percentage stays or drops below 5%.

- The data are placed into a central stream where graphs, file writing and other services can get it. If that queue is backing up you’ll get messages like: “AIQ::enqueue low mem.”

- If a data service is bogging down fetching from the stream you may see one or more of: “AIQ::catBlocks low mem”, “GraphFetcher low mem…”, “Write queue low mem”, “Trigger low mem”.

- The Metrics window (Ctrl+M) gathers these readouts making it easy to monitor run health. Be sure to read the help file for that window.

## How to Report Bugs

If something unexpected happens while running SpikeGLX try to gather these two files for diagnosis:

1. A screen shot that covers as much context as you can get, including any Windows message box about the incident. You can make a screen shot by pressing `shift + Print-Screen`. This saves a picture file to the clipboard. You can then paste the picture into MS Paint and save that as a `jpg` image.

2. The Console window’s log. If the program is still operable you can use command `Tools/Save Log File...` This is the best way to get the log content because it provides some context about what SpikeGLX was doing before the error. Alternatively, if a run has quit due to an error, SpikeGLX saves a brief file with the same name as your run and next to the bin and meta files. It’s called `runname.errors.txt`.

If the computer is hung so you can’t save files, the next best thing is to write down any error messages you see in dialog boxes and the Console window.

## Memory Leak

Many users reported memory leaks, especially when using Nvidia cards after updating to Windows 11 version 24H2 in late 2024 and early 2025. Windows updates KB5058499 and KB5060999 should have fixed this issue.

Separately, Nvidia acknowledged a potential memory leak when using NVENC hardware encoding. They provided a fix in GeForce driver 581.29, released on September 10, 2025.

We experienced this issue ourselves and repaired by getting the latest Nvidia drivers.

## Graphics Problems

### Fuzzy Text

“Why is the text in my SpikeGLX controls, menus and log window so tiny and hard to read?”

Try altering the following Windows setting:

1. Right-click on your Windows desktop and select ‘Display settings.’
2. Click ‘Advanced scaling settings.’
3. Find the button called ‘Let Windows try to fix apps so they’re not blurry.’
4. Turn this feature OFF. – Yes, disable it.
5. Quit and restart SpikeGLX.

### Black Graphics

“Why do the graphs and shank views look mostly black?”

You likely have missing or old OpenGL drivers. Follow these steps:

1. Get and install the `Realtech VR OpenGL Extensions Viewer`. The installer app is called GLView. If the link doesn’t work, Google for ‘glview’.

2. The installed ‘OpenGL Extensions Viewer’ app is under the ‘Realtech VR’ folder in your Start Menu.

The viewer displays info about your installed graphics hardware, your current version of OpenGL, enabled features, and more.

There is a link in the app to help you find the latest drivers for your card.

### Graphs Flicker

“Why do the Graph window panels appear to flash or flicker?”

This is usually due to older slow graphics hardware…

Optimal display settings are discussed here in the User Manual. Follow those guidelines first, which are oriented toward optimizing DAQ performance.

If flicker persists, try updating your graphics drivers, and if that still doesn’t help, you can try changing the `Graphics Control Panel` setting to use the separate dGPU card for SpikeGLX. Core-i7, Core-i9 and Xeon are perfectly fine using a dGPU. Core-Ultra has longer latency, so in this case, be mindful that using the dGPU isn’t dragging down your DAQ performance.

## Remote Desktop

“Can I use Windows Remote Desktop Services (RDP) to check up on SpikeGLX remotely?”

- For Phase3B2 and later: No. These versions of SpikeGLX use a later release of OpenGL that is incompatible with RDP. There are many other remote control apps that do work fine, like AnyDesk or TeamViewer.

- For Phase3B1 and Phase3A: Yes you can; it generally works, but to use Audio Out, there’s a tip needed to make it work, and a hitch that could cause it to crash.

### Audio Output Tip

You probably already know that you have to enable Audio redirection on the client computer from the Remote Desktop Connection dialog: `Options\Local Resources tab\Remote Audio\Settings...\Play on this computer`.

However, you might also have to enable sound redirection on the host computer that’s running SpikeGLX. Do that by running the Windows Group Policy Editor application: From the Window Start menu, use the `Run` option to launch `gpedit.msc`. In the editor, navigate down to:

        Computer Configuration\
        Administrative Templates\
        Windows Components\
        Remote Desktop Services\
        Remote Desktop Session Host\
        Device and Resource Redirection\
        Allow audio and video playback redirection

Make sure this is set to `Enabled`.

### Audio Output Crash

You should be fine in an RDP session turning sound on or off via the `SpikeGLX Audio Settings` dialog `Apply` and `Stop` buttons. However, if you quit your RDP session without first stopping the audio, SpikeGLX will crash on the host computer. Manually stop audio output and then close the RDP session.

> Programmer note: If I could detect an event that tells me an RDP session is about to close, I could programmatically stop the audio and prevent the crash. While there does exist a Windows message: WM_WTSSESSION_CHANGE with wParam WTS_REMOTE_DISCONNECT, it arrives after the session is already closed: too late to prevent the problem. No preceding message traffic predicts an impending disconnect.

fin