720p50 is perfectly blu-ray compilant

1280x720@25fps is not compliant with Blu-Ray or AVCHD. At that resolution you need 50fps, 59.94, or 24fps. It also must be progressive. The pictures are "really stored" -- but on the other hand, since they are exact duplicates they use very little space (by the nature of compression).

I see, thanks. It's clear now where the need for duplication comes from. x264 should encode these exact duplicates very efficiently. On the downside I noticed that the frame duplication roughly doubles the encoding time. So if I understand correctly one way of avoiding the duplication while being compliant with standards would be to 'slowdown' to 24 fps (AssumeFPS(24)) and resample the audio accordingly (i.e. accept the lower pitch). My Sony S357 (=S360) accepts and plays the 720p@25fps on a DVD5 without problems as AVCHD btw :cool:.

For 1280x720p resolution: Does 24 for a compliant encode mean 24.0000 fps, or 23.976024 fps (=24000/1001)?

both are supported. 720 supported as Progressive only with 23.976, 24, 50, 59.940 framerates in Blu-Ray standard

jdobbs, shon3i: Thanks for enlightening me. I was a bit confused because I don't have the BD specs at hand.

:thanks: I will bookmark your post! Added: Tables 9-25 to 9-27 do not include 1440x1080, 720x576, 720x480. I am aware that this is going to leave the scope of BD-RB, so just for my understanding: If I want to backup a 720x576 PAL DVD with x264 (without upscaling to 720p) and stay Blu-Ray compliant I need to do this interlaced (25 frames / 50 fields), correct? (I remember that similar has been discussed somewhere in the forum but I didn't find it ....)