[jjd-uk]

Optimized operation should take the properties of the 1st track in a playlist and use this to setup the audio output properites, and then keep them unchanged for the remainder of the playlist. So if the first track is 44kHz then 44KHz should be used for all remaining tracks in playlist even if some of them are 48kHz. Since audio properties should remain unchanged between tracks then there should be no delay, since it's the only mode that can allow for gapless playback.

Best Match however always seeks to match each track with the nearest matching set of audio output properties, so this allows for sample rate to be changed between tracks. So if first track is 44Khz and next track is 48kHz it will change audio output sample rate to match. In such cases there maybe a small delay as Kodi recreates the ausio sink with the new properties.

[Buschel]

Optimized operation should take the properties of the 1st track in a playlist and use this to setup the audio output properites, and then keep them unchanged for the remainder of the playlist. So if the first track is 44kHz then 44KHz should be used for all remaining tracks in playlist even if some of them are 48kHz. Since audio properties should remain unchanged between tracks then there should be no delay, since it's the only mode that can allow for gapless playback.

This was also my understanding. But is the rate changed when you leave the automatic progression to the next title and manually select another song from the playlist or skip to the next track?

[hurricane51]

Either way, makes no difference. Letting it play continuously or using the button to skip ahead.

[hurricane51]

I just made another playlist (a mix of FLAC and MP3) and confirmed my previous results. Any change in sampling rate will delay that song. If it's a change from 48 to 44, any subsequent songs of 44 kHz after the first will play properly. At no time will the 48 kHz play properly. This is exactly the behavior of Optimized or Best Match, whether letting the playlist play to completion or skipping through the songs. Switching to Fixed and they all play properly. However the settings are supposed to work, they are not doing so on the two systems I've tested. I hope to bring a third system into the mix, but have been having trouble contacting the user. I'll let you know. 

Oh, incidentally, having the Upscaling enabled or disabled makes no difference, and it works as it should.

[HeresJohnny]

If you want gapless over quality, I suggest trying DIRECTSOUND instead of WASAPI as sound output.