1080i50

[Jonathan McLeod]

Posting in this forum as I couldn't think of anywhere better for this topic.

Blu-rays of UK produced TV are usually encoded in 1080i50 to support the 25fps that UK TV is broadcast in.

My understanding of the way interlaced encoding works is that for every 1/50th frame, half the pixels (essentially 1920x540) update and the the 2nd half update on the alternating frame (another 1920x540), but this is actually played back on your device at 25fps so every frame is full 1920x1080 just like a standard 1080p24 stanard blu-ray would be.

If that is the case, then why do I so often see in this forum 1080i versions being considered inferior? Is there actually a quality difference? And if so, why?

I can understand why you wouldn't want things that were orginally shot at 24fps being displayed at 1080i50 and vice versa.