Visualization fun with GStreamer

Visualization fun with GStreamer

I have a Mini-ITX box connected to my TV. It worked very well on my old CRT TV, but now I have a Full HD TV. It went from 720×576 to 1920×1080: five times the pixel count (exactly!), or over 100MB/s (bytes, not bits of course) of raw video. It’s not all that much, but it’s way more than what the Mini-ITX can handle. With the magic of graphics hardware, however, it can show lower resolutions scaled up to 1920×1080 without breaking a sweat.

I had a lot of issues trying to get some music visualization running on it. There’s no way the poor thing can generate 1920×1080 pixels worth of visualization, let alone push it out to the TV. libvisual, the closest thing to a visualization standard there is, didn’t appear to have simple command line apps that you could point to a music file and hardware scale the visualizations to fullscreen.

There was projectM though, which has a clever system of capturing audio from the Pulse audio system and visualizing it with OpenGL scaling. That way you can use any music playing app you want, at any resolution you care to render and display. Unfortunately, the Openchrome drivers for the VIA hardware and the Qt OpenGL component really hated each other.

But hey, we have GStreamer!

gst-launch-0.10 pulsesrc device=alsa_output.hw_0.monitor ! queue ! audioconvert ! libvisual_infinite ! video/x-raw-rgb,width=640,height=360,framerate=25/1 ! ffmpegcolorspace ! queue ! xvimagesink

Grab audio from the pulse monitor device, run it through libvisual to get a visualization at the specified resolution, and show it through xvideo. All my requirements summed up in about two lines of gstreamer goodness!