Tutorial 4: Speed droops

Marker list and correction curve

After defining and adjusting the third Spline marker, your marker list looks in such a way:

Here are registered the spline markers with its exact parameters (frame and correction value). The graphic representation in the correction curve is however more suitable to see and judge the sound deformations at first sight. At our example we want to explain shortly, how the correction curve is to be interpreted.

The fact that the basic speed of the sound was changed is shown by the grey line, which indicates the resulting correction value course. This line is falling in all, i.e. the basic speed was slowed down. The reason for this is that in the last spline marker the correction value is smaller than in the first.

The light blue curve shows the speed changes minus the basic speed and, thus, illustrates directly the compensation of speed droops. This curve is rising in the first part of the video, which means that the sound is played there slightly faster than the basic speed. That is necessary, because at the middle marker the sound came a little bit too late and, therefore, must be slightly accelerated to there. In the following the sound is gradually slowed down (falling curve), until picture and sound fit, in the end, also at the third marker.

Note: The correction curve gives only information regarding the tendency of the speed changes, but states nothing about their amount. In other words: Whether you manipulate the playback speed by the fraction of a percent or by the tenfold, is not evident here.

The project analysis function

Before ending of every AV Adjust project, therefore those places should be inspected carefully, where the light blue line runs most steeply (fastest or slowest speed), as well as "close bends", i.e. rapid and possibly audible changes of the speed. The project analysis function offers the possibility to examine the project concerning such critical areas.

To do this, call the menu command Project | Analyze project .... It appears the following window:

Note: All indicated values refer to the audible part of the audio track. Areas faded out by cuts or option markers are not analyzed.

Decisively for the quality is in particular the last entry "Maximum sound speed change", because speed changes are those effects which become earliest audible and disturb noticeable. Inspect the project therefore at the frame indicated here. If the pitch change is not perceptible there, you can assume that "wow and flutter" caused by the tempo adaptations is nowhere to be heard.

By means of the menu command Project | Start calculation ... you can finally write out the finished video.