diff --git a/lib/util/stream_utils.js b/lib/util/stream_utils.js
index 96ce590ec4..10a5d677b0 100644
--- a/lib/util/stream_utils.js
+++ b/lib/util/stream_utils.js
@@ -765,6 +765,7 @@ shaka.util.StreamUtils = class {
     if (codec.includes('avc1')) {
       // Convert avc1 codec string from RFC-4281 to RFC-6381 for
       // MediaSource.isTypeSupported
+      // Example, convert avc1.66.30 to avc1.42001e (0x42 == 66 and 0x1e == 30)
       const avcdata = codec.split('.');
       if (avcdata.length == 3) {
         let result = avcdata.shift() + '.';