Videos are not properly cached

[Arnei]

The videos from opencast are not properly cached, but redownloaded. This is relevant for waveform generation, which seems to download the whole video file, but also when jumping to different parts of the videos in the cutting view (new range requests are send everytime).

[lkiesow]

The important bit is that this is fast enough for a 90min recording. If that works, downgrade the priority to low.

[Arnei]

Did a bit of testing.

• Videos are not completely preloaded in the players. Instead, only a small part is preloaded to ensure smooth playback. --> When you make larger jumps on the timeline (as you are prone to do in a video editor), a new range request is triggered. This can cause a slight stutter of up to a second, which may not be too bad.
• Independently from the players, the Waveform Generation does download one whole video before it generates anything --> Obviously a problem for low bandwidth users
  • In Chrome the download will sometimes be paused when interacting with the website
  • Video is redownloaded each time you reload the website
  • Waveform generation is not completely async. For a ~100MB video, interaction with the website was not possible for about 2 seconds.
  • Shows "Generating Waveform" while downloading, shows "Waveform could not be generated" while generating.

[Arnei]

Changing the priority from high to low because:

• We deemed slight stuttering when a range request is triggered to not be a big problem.
• Downloading a whole video to generate a waveform is also acceptable, as preview videos with a small enough file size can be generated and used in Opencast. Should this still present a problem in the video, Opencast could either generate an audio file from a video and sent that to the frontend, or we can fall back to Opencast generating the waveform instead of the frontend.

Other problems mentioned are separate issues and should therefore be discussed in separately.