ntsc video signal to image file with PXI-5114?

[jason1]

Is it possible to use a PXI-5114 digitizer to capture a NTSC video signal and reconstuct a single frame to be saved as an image file?

[Kyle_A.]

Hi Jason,

Yes, it is possible to do this.  Here is an example of what you would need to do video triggering capture with a digitizer.

[dansch]

Hi Jason,

I think the example Kyle posted is for the NI 5112 digitizer, which has to use an IMAQ board to video trigger since it does not support video triggering. However, the 5114 is one of the boards that does support video triggering, including the NTSC format. More information can be found in the digitizers help manual (online here). If you are using LabVIEW, we have a basic video triggering example that you can take a look at and try out (the example is called "niScope EX Video Triggering.vi" and can be found from the LabVIEW Example Finder or by going to Start » Programs » National Instruments » NI-SCOPE » Examples from your Windows start menu). If you need to acquire the entire frame, that will probably require you to sample a very large amount of data, in which case you may or may not be able to stream it to disk. In the best case, you can acquire the entire frame in a single record without having to do any streaming to disk. Otherwise, you may need a digitizer that can stream high throughput to a hard drive RAID or something of the sort if you plan on acquiring a large amount of data. Worst case is that it is just too much data, too fast, and it cannot be streamed. Perhaps with more details of the signal and your expected sample rate, we may be able to provide some additional guidance on the possibilities of acquiring the entire frame. Hope this helps!

[dansch]

Hi Jason,

I did some quick research into NTSC and it appears that a frame consists of 525 scanlines, and the refresh rate is about 30 fps. This means that if you are sampling at the maximum rate of 250 MS/s, acquiring an entire frame would take about 33.3 ms which equates to a little under 8.4 MB of data (each sample is 1 byte since we have 8-bit resolution on the 5114). As long as you have a higher memory option digitizer, you should be able to acquire the entire frame without needing to stream it to disk (ie- the entire record should fit into the onboard memory of the digitizer at one time). You may choose to try and fetch the entire record at once into LabVIEW and write it to a file, or fetch the record in chunks (within a loop) and then write it to a file, but it should not be a problem either way.

Regards,

[jason1]

The "niScope EX Video Triggering.vi" is where I started.  My question is if there is a tool that can convert this complex waveform into a static image file that can be saved to a picture file.  I was hoping that I could send a NTSC test pattern into the NI 5112 and then see the image on the PC monitor.  I understand it is a big task to break apart the analog waveform and convert it to a digital file but it is a standard NTSC image so i thought someone might have done this already.

Thanks for your help.

Jason 

[dansch]

Hi Jason,

Thanks for the clarification, I am glad to hear that you were able to get the acquisition working. I have not seen such a set of software directly made for this, but that would be a neat tool indeed. I do know that there is functionality similar to this that I have seen when using our VideoMASTER software. I output a frame on a generator, acquired it with the digitizer, and I was able to view both the actual waveform graph of the signal and I was able to look at an image of what the signal represented. For the most part, just to make testing simple, I used color bars, but I was able to see the color bar images all the same (for example, see the first image at this link to see the software and it actually shows the color bar image, which was created from a frame of video data). Unfortunately, outside of VideoMASTER, I doubt you will be able to find this type of program, as I am sure it took a bit of effort to create, but it is definitely possible and has been done. Best of luck to you!

[dansch]

Just for the sake of future reference and completeness on the topic, I wanted to confirm that VideoMASTER 3.0 had this feature added, and will in fact convert a video frame to an image file. I know a program can probably be made to do this, but I am not sure how much time and effort may be required, so VideoMASTER may be an alternative. Once again, best of luck!