Sometimes the association does not stick initially. If not, highlight the mixer viewer with the problem, change the mixer arrows to point up, and reassociate.
-\section{Audio/Video sync via Waveforms/Timecodes}%
+% For html, make sure using below is different from via in subsection
+\section{Audio/Video sync using Waveforms/Timecodes}%
\label{sec:audio_video_sync}
\index{audio/video sync}