Hello,
it will be very interesting to publish articles about current state of performance for various audio/video libraries available - GStreamer, ffmpeg, SoX and so on. Currently, GStreamer are moving from liboil to orc, ffmpeg gets more developer love, SoX devs are releasing regularly versions too.
Measurements can be done for simple audio processing like converting from one format to another, resampling, and similar parameters for video.