Playback was stuttering badly in the Avidemux window. New download of vers 2.7.1 on new Dell Optiplex 3060 with Windows 10 Pro, version 1803.
Go to Preferences>Display. Under "GUI Rendering Options", check "Enable openGl support".
Stuttering playback after going to the previous picture, unrelated to selected video output, was a regression in 2.7.1, fixed a few days after the release. Please use at least the latest release (2.7.3) or much better the latest nightly (currently 190630), either the one built with Microsoft Visual Studio C++ on Windows https://avidemux.org/nightly/vsWin64/ (https://avidemux.org/nightly/vsWin64/) or cross-compiled with MinGW on Linux https://avidemux.org/nightly/win64/ (https://avidemux.org/nightly/win64/).