IQ File Capture | Playback problems
I am trying to playback a captured file (see Capture_1.png & Capture_2.png), but having issues with the playback using both the File Reader and File Source blocks. The file capture seems to be working without incident. The File Reader does not seem to output to the SpectranV6 correctly, most likely due to the Yellow Tx warning once I start the SpectranV6.
Without the SpectranV6 started, I do see the output from the file reader to the display (of course), BUT I do notice a rather long delay when the files gets to the end and wraps back to the beginning for replay (FileReader_1.png). In this wrap-around, the RTSA software graph display(s) freeze (i.e. no updates) for about 2-3 seconds.
With the SpectranV6 started, I get yellow on the Tx block of the SpectranV6 control; the error states Tx Transmitter Channel Input Underflows, Stream source data rate is too low, Input processing chain too slow (FileReader_2.png).
When I replace the File Reader block with the File Source block, I cannot even get the captured file to read/display properly. First, the File Source block does not display the waterfall image of the captured signal, and second it reads through the file extremely fast (actually instantaneously). I've read through the forum block descriptions, and the other users issues with this, but nothing seems to help with this issue. Any guidance would be greatly appreciated.
You need to add a Time Offset (>=30ms) as a "buffer" and activate the Emulate Realtime checkbox if you want to stream IQ data.
See posting at: https://v6-forum.aaronia.de/forum/topic/file-source-block/#postid-1282
Yup, I've tried that too! Interestingly, the Emulate Realtime checkbox does not show (see below figure).
Possibly next question is how good is the computer that I'm running on?
Intel NUC 11, I7-1165G 2.8-4.7GHz
16GB DDR4-3200
512GB H10 Optane SSD
1TB SDXC UHS-I Card (for larger captures)
USB 3.2 Gen 2x1
GeForce RTX2060
Quote from CorNic East on 03/05/2022, 15:30Yup, I've tried that too! Interestingly, the Emulate Realtime checkbox does not show (see below figure).
That option was added to the FileSource block in build 10361, it is not yet available in the current stable version you're using. The FileReader block should have it though.
Quote from CorNic East on 03/05/2022, 15:411TB SDXC UHS-I Card (for larger captures)
Note that recording/replaying IQ data can exceed transfer rates of 400 MB/s or more (depending on settings), so basically any storage medium other than SSDs will have problems with that. In extreme cases even SATA SSDs might be a bottleneck.
For small records not a problem as they can be buffered in memory. For large multi-gigabyte records though this can become a major problem.
Understood on the transfer rates. Would I be assuming incorrectly that when a user reduces the Span of the measurement, that the IQ rate is remaing the same?
If this is the case, it would sure be nice to have the ability to down/up sample the data for reduced span measurements, easing off on the IQ through-put requirements. Might be a very nice set of blocks (in the FPGA).
I have attempted to enable Emulate Realtime checkbox in the File Reader block, but this did not have any effect with the Tx errors.
How do I go about getting the 10361 build?
Quote from CorNic East on 03/05/2022, 16:59Understood on the transfer rates. Would I be assuming incorrectly that when a user reduces the Span of the measurement, that the IQ rate is remaing the same?
Reducing span can affect the required transfer rate, as can compression ratio and IQ Samplerate. When recording you can see the current transfer rate in the FileWriter block, so simply test it out when using your SSD as storage which parameter combination results in which transfer rate requirements (the actual data recorded can also have some impact as not all data compresses equally well).
That is when recording the IQ stream directly from the Spectran V6 block. When processing blocks are added in between there are obviously a lot more variables.
interesting information
We have updated the Tx operation.
Please check out the latest missions and documentation here:
https://v6-forum.aaronia.de/forum/topic/using-the-tx-example-missions-manual-demodata/
