Bug 514673

Created attachment 188571 [details]
a comparison between the same graph in Audacity and Kdenlive. note how peaks differ in upper/lower parts of Audacity graph, but Kdenlive one always displays the peaks symmetrically at both sides.

Today a user in Discord was complaining about the new audio waveform graphs (introduced some versions ago).
He stated that he preferred the previous graphic style that only showed "one half" of the waveform, as it was able to more efficiently show the differences in audio using the same vertical screen space.

I understand most audio programs show the complete waveform graph, and in that sense, it's expected that Kdenlive also show audio graphs that way. 
Still, I think there's a point in the claim, and perhaps there could be an option in Preferences for displaying just half of each channel's graph?

Also, related to this, I've found that the waveform graphs Kdenlive draws have one problem:
What they show is not the real waveform of the audio, but a sort of "half wave"* duplicated to both sides of the zero line.
* it seems to overlap both halves on top of each other, and draw that same result to the upper and lower parts of the graph.

It's frequent that the lower part of the graph is not equal to the upper part (as shown in the attached image), but in Kdenlive both halves of the signal are always shown the same.
I don't know if this was on purpose or just a byproduct of the code refactoring done.

Thing is, if the graphs just show one duplicated half, all purpose in using more screen space to show the whole waveform seems to be lost (i.e. we're just using more screen space for nothing that couldn't be shown even bigger using half of it). 🤷‍♂️