Dynamic File Names in GNU Radio Companion

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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.

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More GStreamer Tips: Picture-in-Picture Compositing

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In a previous post I gave a few examples showing how simple text overlays can be added to any video stream in GStreamer. Now it’s time to look at compositing between two or more video streams, also called picture in picture. As you’ll see it is still very easy to achieve even when using nothing more than the gst-launch command line tool. First we look at some basic examples, then we finish with a more complex “Live from Pluto” video wall.

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Simple time-lapse video with gtreamer and ffmpeg

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I have experienced an unexpected spin-off while fooling around with GStreamer and my Logitech QuickCam Vision Pro 9000 webcam: A simple and easy way to autonomously capture and render time-lapse videos.

One of the advantages of webcams compared to other digital still and video cameras is that it can be controlled from a computer and the captured frames are transfered from the camera to the computer in real-time using the USB interface. This is pretty much the definition of a webcam and this feature is indeed very convenient for capturing time-lapse videos. Unfortunately, the image quality of webcams has not been anywhere near good enough to make nice looking time-lapse videos but this has changed over the last few years and is continuously improving. The results presented in this article are captured using my Logitech QuickCam Vision Pro 9000 – one of the greatest UVC cameras out there.

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A Weekend with GStreamer

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Gstreamer LogoThis weekend was dedicated to learning and experimenting with Gstreamer – an open source library and framework for constructing audio and video processing pipelines. Despite the weekend being spoiled by lots of bad luck (power outages, Internet down, etc.) I managed to beat the hell out of Murphy and get some work done!

My hidden agenda is of course finding a good audio/video library to accompany a software defined radio created using GNU Radio and the Universal Software Radio Peripheral (USRP), and to eventually be able to transmit real time high definition video over the air. While GNU Radio and the USRP can take care of everything related to software radio and RF, I am still looking for a good framework for flexible audio/video processing.

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A Weekend with GStreamer

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Gstreamer LogoThis weekend was dedicated to learning and experimenting with Gstreamer – an open source library and framework for constructing audio and video processing pipelines. Despite the weekend being spoiled by lots of bad luck (power outages, Internet down, etc.) I managed to beat the hell out of Murphy and get some work done!

My hidden agenda is of course finding a good audio/video library to accompany a software defined radio created using GNU Radio and the Universal Software Radio Peripheral (USRP), and to eventually be able to transmit real time high definition video over the air. While GNU Radio and the USRP can take care of everything related to software radio and RF, I am still looking for a good framework for flexible audio/video processing.

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MPX4115A Pressure Sensor with Arduino

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Today I have successfully interfaced an MPX4115A pressure sensor to my Arduino board. The MPX4115A is an analog pressure sensor that outputs an analog voltage proportional with the pressure. The setup is the same as the previous one with the TMP102 temperature sensor; I just added the pressure sensor, a few decoupling capacitors and connected it to an analog input of the Arduino board.

MPX4115A pressure sensor connected to an Arduino Duemilanove.

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TMP102 Temperature Sensor with Arduino

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At long last, I have found some time to start playing with Arduino stuff!

I decided that good starter project would be simple weather station that reads temperature, pressure, … sensors and shows them on an LCD display. Below you will see a first cut using a TMP102 temperature sensor from Texas Instruments mounted on a breakout board from Sparkfun.

Arduino mock-up

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UNITEC-1 Tracking Report

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I’m sorry to report that despite coordinated efforts between Japanese and European teams we have not been able to receive any signal from UNITEC-1 over Europe. Japanese ground stations were able to receive both the orbit determination downlink and the major/minor data downlink during the first pass after launch; however, the signal has been lost during the first mission day sometime between LOS over Japan and AOS over Europe.

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Successful UNITEC-1 launch and separation!

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The launch of H-IIA F17 carrying AKATSUKI, IKAROS, UNITEC-1 and three cubesats was successful! So was the separation of UNITEC-1 which was confirmed at 22:48 UTC (Epoch time 22:46:20 UTC). We meet tomorrow afternoon at OZ7SAT for the first communication window predicted to begin around 17:21 UTC. At that time UNITEC-1 will already be at … Read more