macOS 10.15 QMediaPlayer setPosition() has 10 second granularity

1. Description

macOS 10.15 QMediaPlayer setPosition() has 10 second granularity. The millisecond value is rounded to nearest 10000ms. Example:

setPosition(1000) -> position set to 0s
setPosition(2000) -> position set to 0s
setPosition(8000) -> position set to 10s

This makes setPosition() unusable for many applications.

2. Possible root causes

See line 687-689 of qtmultimedia/src/plugins/avfoundation/mediaplayer/avfmediaplayersession.mm from code.woboq.org:

687 CMTime newTime = [playerItem currentTime];
688 newTime.value = (pos / 1000.0f) * newTime.timescale;
689 [playerItem seekToTime:newTime];

On 689, there is a call to a now-deprecated variant of AVPlayerItem seekToTime method. This might be causing the problem.

Also, there might be a numerical issue on line 688 (should this be done in double precision?).

3. Proposed fix

I think it should suffice to replace the existing call to seekToTime with the following (non-deprecated) variant:

seekToTime:toleranceBefore:toleranceAfter:completionHandler:

toleranceBefore and toleranceAfter should be set to kCMTimeZero to request sample accurate seeking.