Put a soundwave form image alongside the timeline

[dascritch]

from dascritch/ondemiroir-audio-tag#52

• Calculated by the browser ? may be too heavy and impact battery usage
• Use a remote image with the soundwave form ?
• Use a remote data with the soundwave form, rendered as SVG ?

[dascritch]

Spectrogram generator:
https://unix.stackexchange.com/questions/200168/how-to-create-the-spectrogram-of-many-audio-files-efficiently-with-sox
sox sound.mp3 -n remix - spectrogram -o wave.png -x 2000 -y 65 -r -m
tinypng # sox image is a little bit huge

or https://askubuntu.com/questions/536072/generate-waveform-image-for-audio-file

Please note that the images do not really need to be bigger than 4000px20px (21900 , 2*10). Be wise, resize and recompress.

You will also need an optional parameter in live chapter editor, it may helps ^^

[dascritch]

Need to create new tags in cpu-15 template theme

[dascritch]

Done there dascritch/plugin-dotclear-cpu-audio@029382f