This project uses one of the low cost 128 x 64 OLED dsiaplays that can be found on ebay to give a VU meter for USB audio devices.
The display uses the SSD1306 controller IC connected via I2C and is connected to the XMOS MFA USB audio ref design.
It uses a function inline with the I2S loop to peak hold and decay. A separate task reads this info and sends it out to the display. It manages about 40 FPS (limited by I2C write speed @ 400Kbp) so quite a convincing effect. I tried and it does actually manage 1Mbps, but do so at your own risk!
Video here - www.youtube.com/watch?v=S7VSKjkmqRs