The Justice League is reportedly longer in HD compared to UHD - why? (and it isn't PAL speedup)
Zack Snyder's Justice League debuted yesterday and in the UK viewers on Sky were quick to pick up that the runtime of the HD version of the film was running to 4 hours and 1 minute compared to the 3 hours 52 minutes listed against the UHD version.
One major site has already stated that the reason for the difference is down to the effects of PAL speedup - this isn't the case as PAL speedup doesn't affect material that isn't in the PAL format; and no HD material is broadcast or streamed via PAL.
We've checked both versions of the film and the actual footage is the same in both. The films themselves also run to the same amount of time - so this additional time for the HD release looks like it is associated with the ads that run before the film.
What is PAL speedup?
Before HD was a thing, TV formats around the world varied - the US and some other countries such as Japan broadcast their TV in NTSC, the UK and Australia and some others PAL and some countries used SECAM. SECAM and PAL were closely related.
PAL had the advantage over NTSC in that it was a higher resolution - 720x576 pixels compared to 720x480 - this meant a sharper image with fewer scanlines. However PAL ran at 25fps and NTSC 24fps - the latter matched the cinema. In order to broadcast films in PAL there were a couple of options; the first was to repeat a frame every second which resulted in noticeable judder in panning shots in particular. The other was to just run the PAL broadcast and footage by speeding things up by one frame per second. The latter was most common and resulted in films and TV shows running at around 4% faster in the UK and other PAL countries than NTSC.
Sometimes no attempt was made to correct the resulting pitch increase in the audio as a result of the speedup and many people were surprised to hear their favourite films and soundtracks sounded noticeably different when watching in non PAL formats.
PAL and NTSC differences were very much at the centre of attention back when DVD was taking off with many people importing discs from outside of the UK. However, Blu-ray and HD formats generally run at 720 or 1080p at 24fps worldwide and the same frame rate applies to 4K material.
So no, PAL speedup definitely isn't the cause of Zack Snyder's Justice League running longer in HD, it's just the ads.