SyncPlayer 1.6.6 - quality default, threaded downloads, finer seeking

Added

• YouTube playback quality setting: Best available, 2160p, 1440p, 1080p (default), 720p,
  480p or 360p. A change applies to the next video loaded, without a restart.
• Download connections: 1-16 (default 8) parallel fetches, using yt-dlp's concurrent
  fragments plus chunked downloads, the way a download manager works. Adjustable per
  download and remembered.
• Settings dialog in the header for playback quality, download connections and the seek
  distance.
• The seek buttons step by the Jump distance instead of a fixed 10 seconds, and show the
  distance on the button.

Removed

• The URL buttons beside the source fields: a link can be pasted or dropped straight into
  the field.