BDs encoded at precisely 24fps - is this wrong?

[Mentasm]

I've noticed that a few of Optimum's recent and forthcoming BD releases are encoded at precisely 24fps, not 23.976fps like every other BD I own (incliding all of Optimum's older releases). When watching these discs through my BD-P1400 with 24Hz output to my Toshiba 42Z3030D with film stabilization set to standard (120Hz 5/5 pulldown mode) I see regular glitches in the video, almost like a frame skip. I have seen this problem before, when Samsung broke the 24Hz output on the BD-P1400 with an earlier firmware release.

As far as I'm aware, players with 24Hz modes actually send at 23.976, not exactly 24. Is this correct? If so, could the precise 24fps encoding of the video in conjunction with the player trying to send it at 23.976 be what's causing these visual 'hiccups'?

[quexos]

Wow I never heard of a fraction of unit being involved in the FPS. Or do you mean that 24 Frames come in one second and a tiny fraction of the next second ?
Anyways the "Hiccups" are caused by the difference between 24 and 25 FPS in Pal European standards (To the best of my knowledge)

[Mentasm]

No they're not. PAL has nothing to do with Blu-ray at 1920x1080. Even if it did, going from 24fps film to 25fps PAL doesn't cause artefacts. You're thinking of NTSC with pulldown.

The reason the frame rate is 29.976 is for legacy reasons. NTSC is not precisely 30fps/60Hz, it's 29.97fps/59.94Hz. For BDs the original 24fps are slowed down by 0.1% to be output at that speed by any capable player (PS3, most standalone BD players). I've checked virtually all of the BDs I own and the only ones encoded at 24fps are the ones from Optimum. All of the others are 23.976 (well, my software player rounds it up to 23.98, but you get the idea).

I'm just trying to get confirmation from someone with more video knowledge than me whether or not this falls outside of spec for BD? It certainly seems to break 1080p/24 output.

[ToEhrIsHuman]

Actually, the BD spec includes BOTH 24Hz and 23.976Hz field rates so as to which component is causing a problem is anybody's guess.

[Mentasm]

Yeah I know it includes it, but I was under the impression that stuff destined for playback in a home environment was encoded at 23.976 and that all BD players with a 24Hz mode actually output at 23.976. I've never seen a disc from a major studio that isn't. If this is wrong then fair enough, but everything I've read in the past couple of days seems to indicate to this. I've even seen references to certain TV and BD player firmwares being 'broken' for using exactly 24 instead of 23.976. Indeed, an earlier version of the firmware for my BD-P1400 broke the 24Hz output, givign this same jittery appearance (presumably ebcause it was trying to output 23.976fps at exactly 24fps - this appears to be the reverse). It's all a bit confusing.

[NutsAboutPS3]

How are you identifying how the disc is encoded?

I'm just asking because I've always noticed that some discs have a kind of juddery appearance, while others don't, but the info display on my TV just states 24Hz for all discs.

I doubt that any player converts between 23.976 and 24 because I'd expect this to cause problems if the audio is bitstreamed; the player would need to decode it, speed it up or slow it down, then re-encode it.

[Mentasm]

The software player I use tells me the frame rate. Most BDs show up as 23.98, these new ones are exactly 24. I'm not suggesting anything is altered on the fly though.

Basically what I'm trying to figure out is if video encoded at exactly 24fps would stutter every now and then if output at 23.976fps (as is my understanding of how BD players 24Hz modes actually work).

Or you could look at it the other way, would 23.976fps material stutter at 24fps? It think this is what happened with the Samsung player and also some LG TVs (found some info while Googling).

I'm just trying to get concrete info before I go to the label and tell them. It seems mighty coincidental that I only see these glitches on the 24fps discs.

[dialog_gvf]

Originally Posted by Mentasm

No they're not. PAL has nothing to do with Blu-ray at 1920x1080. Even if it did, going from 24fps film to 25fps PAL doesn't cause artefacts.

Besides the BIG audio one?

(Or do players apply a pitch correction?)

Gary

[Mentasm]

It's clear that I'm talking about video.

[Clark Kent]

BDInfo, the freely available computer program, will give this information for any BD. I think for film based material Optimum is encoding these discs wrong and some BD players are having problems playing some of this material.

[Mentasm]

That's interesting. Have you read any other reports? Obviously I have the problems, but I've not heard of anyone else reporting them. And yeah, BDInfo is very useful.