Just to expand on this a little.
drew_nickel wrote: ↑Tue Apr 26, 2022 7:35 pm
1.) Is the reason the FEL layer file size is so much bigger than the MEL version because the FEL contains 12bits of color data, which has exponentially more color data than the 10bit MEL version?
When dealing with DV Profile 7, you have a Base Layer and an Enhancement Layer.
A 12-bit 4K master is graded and then analyzed by DV software and processed into a 10-bit 4K HDR10 base layer, a 10-bit 1080p enhancement layer, and the Reference Processing Units (RPUs) containing dynamic metadata — characteristics of the brightness from scene to scene and the tone mapping trims for different display capabilities.
The EL contains the residual video signal that's the difference between the 12-bit master and the HDR10 BL.
An FEL contains the full 1080p video stream with the residual video data plus the RPUs.
An MEL has the video data stripped out; it has a null video stream or mid-gray static field, and is just used to carry the RPUs. Or, as I understand it, if there was only a 10-bit master produced there may have never been the extra 2 bits of color data available, so there was no video data the FEL needed to carry.
drew_nickel wrote: ↑Tue Apr 26, 2022 7:35 pm
2.) If the mediainfo for a certain movie says this about the FEL layer:
MPEG-H HEVC Video 7564 kbps (10.95%) 1080p / 23.976 fps / 16:9 / Main 10 @ Level 5.1 @ High / 4:2:0 / 10 bits / 1000nits / Dolby Vision FEL / BT.2020
Doesnt it mean the FEL is basically pointless since it was Mastered in 1000nits and 10bit?
The FEL just contains the 2-bits of diff between a 12-bit master and 10-bit BL. It's recombined with the BL in a proprietary DV process to recreate a 12-bit 2160p signal from a 10-bit 4K BL + a 10-bit 1080p EL, so you don't need to worry about the video specs too much. The EL video stream isn't be displayed directly, so the specs aren't really relevant. It's using 10-bits of color @ 1080p resolution to represent 2-bits of color @ 2160p resolution. They used a proprietary hack to stuff the 2-bits of data they needed into an existing video format, 10-bit 1080p HEVC video.
drew_nickel wrote: ↑Tue Apr 26, 2022 7:35 pm
3.) I have a CX (700-800 nits max). Since my display wont even go over 1000 nits (no where even close to 4,000 or 10,000) would I benefit at all from having a DV player capable of playing Dual layer FEL? or would the player basically output the same thing as the single layer MEL version?
The RPU contains trim data — adjustments for different brightness displays — often for 100nits (SDR) and 600nits. When your device's EDID indicates an 800nit max, the 100nit and 600nit trims are used to produce a picture that's as close as possible to the 10000nit or 4000nit or 1000nit master.
That will be true with either an MEL or FEL.
And it's true that the 2bits of color data in an FEL usually mostly represent brightness beyond your display's capabilities.
So in a lot of cases the FEL will contain data brighter than your display can presently handle and it isn't that useful, but in other cases (as shown in the Total Recall snapshots) the FEL video data actually adds more clarity and detail because of the way the data was split apart in the encoding process.
So MEL and FEL encodings are both capable of exceeding the capabilities of most displays, but if you want to be sure you're getting the best possible video quality, you go with the FEL. Without analyzing the contents of a specific FEL video stream, or seeing it rendered with the BL+EL combined, you won't really know what you're missing.
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