The audio still plays at exactly the same speed, only it starts at a different point in time relative to the video. No, MKVMergeGUI does not slow down or speed up audio by specifying an audio delay. If not is there any that kind tool that work wit ALL sounds? This tool works only with ac3 sound or it would work even with dts, dts-hd, true-hd without change the type or the quality of the sound ONLY THE FPS. I simply make 25fps into 23.976 and then add that ac3 audio into mkv file and it was PERFECT.

A LOT OF THANKS MY FRIEND THE PROGRAM EAC3toGUI IT do the job like a jarm. It's just a GUI though, you'll also need to install eac3to and tell the EAC3to Conversion Utility where to find it.

To convert the audio while adjusting it's speed, try this: there's no guarantee the two versions of the video have been edited in exactly the same way. Then if they don't start together, you can adjust the audio delay.

The best bet is to either re-encode the audio and change the speed in the process (some programs refer to it as PAL speedup or slowdown etc) but a better option might be to change the frame rate of the video and leave the audio alone (you'd need to change the 23.976 version to 25fps). The 'stretch by' field would potentially be the one you want, but most audio doesn't stretch too well. If you specify 100ms, then (assuming the audio and video would normally match up) the audio will be 100ms out from start to finish. The option in your screenshot does not change the speed of the video.

Mkvtoolnix gui 25fps to 23.976