Re-encoding of 1920x1080 i50

[Sharc]

Probably not a bug in BD-RB, but seeking clarification for this case:

Original Blu-Ray stream is AVC 1920x1080, 25.000 fps, MBAFF (reported by MediaInfo and DGIndex)
Separating the fields with avisynth show a progressive frame sequence like aa, bb, cc, ..... (bobbing, no timewise interlacing)

I select in BD-RB resizing to 720p.

BD-RB applies a deinterlacing script like:
DirectshowSource("K:\......\00000.m2ts", fps=25, framecount=219775, audio=false)
AssumeFieldBased().AssumeTFF()
ConvertToYV12()
LoadPlugin("C:\Program Files\VIDEO\BD_Rebuilder\tools\decomb521.dll")
FieldDeinterlace()
LanczosResize(1280,720).ChangeFPS(50)
ConvertToYV12()

The encoded VID_00000.AVS.264 (in the BD RB working directory) is reported by MediaInfo as 1280 x 720, 50.00 fps, progressive
Stepping through this file with mpc or DGindex indicates a duplication of every picture.

So finally the qestions:
- Isn't the picture duplication a waste of storage space (bitrate)?
- Are the duplicates really stored, or are they just 'pulled down' for playback?
- Is the movie encoded at 50 fps for Blu-Ray compliancy reasons @ 720 resolution?
- Would a straight (i.e without deinterlacing script) progressive encode @ 25fps be AVCHD compliant?
- Would -for Blu-Ray@720p compliancy- all streams have to be re-encoded to 23.976 fps ('slowdown')?

Thanks.

[shon3i]

720p50 is perfectly blu-ray compilant

[jdobbs]

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).

[Sharc]

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:.

[shon3i]

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:.
Well many combinations are played today on most players.

[jdobbs]

Well many combinations are played today on most players.But, of course, that's not a good reason to support it.

[Sharc]

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

[shon3i]

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

[Sharc]

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

[shon3i]

jdobbs, shon3i:
Thanks for enlightening me. I was a bit confused because I don't have the BD specs at hand.
Here is all what you need :)

http://tom.niko.users.sbb.rs/bdtable.jpg
http://tom.niko.users.sbb.rs/gop.jpg

[Sharc]

: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 ....)