Firefox HTML5 Playback Problem

Note: This HTML5 playback issue is not expected to affect latest Firefox on Windows anymore as of late 2021.

Firefox does not like being fed (through the Media Source Extensions API) small video chunks that do not always begin with a keyframe. When it finishes decoding the buffered frames, it clears its decoder state such that the next time a frame arrives, Firefox must return to the previous keyframe and start decoding all over again. UI3 submits one frame at a time, so this is extremely resource-intensive as Firefox is constantly going back and wasting time decoding the same frames over and over again.

The "Firefox Stutter Fix" option in UI3 appears only when using the HTML5 video player, and causes Blue Iris to produce a keyframe about every 1 second. This reduces the amount of wasted resources (IT IS STILL VERY WASTEFUL), and also causes a distracting pulsing effect in the video unless operating at extremely high bit rates. Mozilla has known about this streaming problem for years but refused to fix it because it only affects an uncommon use-case like UI3's. https://bugzilla.mozilla.org/show_bug.cgi?id=1290840

Keyframes cause this pulsing mostly because of the Max bit rate limit which is enabled by default. It forces keyframes to be relatively small and low quality. You could try turning off the bit rate limit and use a Quality setting in the ballpark of 20-30 to keep the bit rate reasonable. That should drastically improve the pulsing situation, but require more bandwidth for the same video quality as before. And it will still waste resources.

Until there is a better solution, the default and recommended H.264 player for Firefox is the JavaScript option.