Complex sentence: Tens of thousands of videos were posted on the channel while it was active, some only a few seconds long, some as long as eleven hours long, and all featured abstract images and were either silent or with distorted voices and unusual sounds.
Split into simpler sentences: Tens of thousands of videos were posted on the channel while it was active, some only a few seconds long, others as long as eleven hours. All featured abstract images and were either silent or contained distorted voices and unusual sounds.