Shotcut slows down Pulse Audio's playback?!?


#1

This has happened to me too many times to be just chance.

After running Shotcut 18.03.2 for a while, e.g. to export to MP4 a series of projects, the playback of any music in Pulse Audio (11.1-15) running on my Fedora (kernel 4.5.17) is slowed down, just by a little, independently of what software I use, e.g. Rhythmbox or Spotify. E.g. a 3:36 song takes 3:52 to play, that’s a ~7% slower.

Of course, because I am doing encoding and have no GPU, the CPU is maxed out, but can that justify the issue?

Thank you in advance for any insight. Perhaps it’s something we should inform the Pulse Audio maintainers of?

G.


#2

Sounds very strange. Some information that may or may not be relevant:

Shotcut uses Pulse Audio configured for 48KHz. The other common audio frequency is 44.1KHz. Maybe other applications are using that? The difference between the two is 8.8%. But that would be in the other direction (that is, the songs would play 8.8% faster).


#3

Yes it is interesting. Note also that:

  • what I was doing was exporting to a file, so there is no audio output implied by that operation… which means that there should be no use of Pulse Audio, and

  • after encoding finishes Pulse goes back to normal without me doing anything.


#5

I think it is quite plausible.