I have had some time to hack on the GQRX receiver – my experimental AM/FM/SSB receiver implemented in Python (GNU Radio) and qith Qt GUI. Most notably, I have implemented audio recording, playback and squelch.
python
Gstreamer compositing using the GstvideoMixerPad properties
Few weeks agio I posted my notes about picture-in-picture compositing in Gstreamer using nothing else than the gst-launch command line tool. I also wrote that I could not figure out how to use the xpos, ypos, zorder properties of the GstVideoMixerPad element. I got a comment on this note from Jan Schmidt telling that these properties can not be used with gst-launch but are easily accessible from Python. He also gave a very cool example that shows how to use it.
Dynamic File Names in GNU Radio Companion
I needed a quick USRP IQ data recorder today to record the APT downlink from NOAA satellites. This is really trivial to implement using the GNU Radio Companion, but I had to figure out how to use dynamic filenames to avoid overwriting previously recorded data. Of course, I could just rename each file when recording has finished but I am too lazy to do things like that. Using the current date and time in the file name seemed to be a good solution.
This quick how-to explains how to use the Python datetime module to generate a unique filename in GRC.