yusesope wrote: Sat Feb 29, 2020 6:26 pm
I try to answer the questions of some of you.
These are
my personal considerations.
There are several "types" of Dolby Vision:
Double Track Double Layer: BL and EL + RPU (this is the case of Bluray discs where the Base Layer is represented by the first video track and the rest is placed in a second video track)
Single Track Single Layer: BL + RPU (this is the case of DVDFab)
Single Track Double Layer: BL + EL + RPU (my attempt)
There are also two types of EL:
The full enhancement layer (FEL) is a HEVC video stream with embedded Dolby Vision metadata: it requires a SoC to be capable of simultaneously decoding two video streams (base layer video stream and FEL video stream).
The minimal enhancement layer MEL, a constrained FEL, only consists of metadata: it requires a SoC to be capable of only decoding one single base layer video stream.
My mp4 files meet the characteristics listed in section 3.2 (in particular, subsection 3.2.2) of
THIS document and have been generated from a Bluray disc with a Dolby Vision Double Track Double Layer (BL and EL + RPU) without alter any of the components.
It is logical to think that the best profiles for decoding my files are dvhe.04 and dvhe.07 (refer to
THIS document) as they allow to improve the Base Layer using EL and the instructions contained in the RPU metadata.
I do not dwell on profile 07.
I take into account profile 04 (surely those interested in this type of file have a device, such as the new Shield, which does not support profile 07).
In official Dolby documents it is stated that a new Dolby Vision certified device is able to decode a profile 4 MEL bitstream without instantiating a secondary HEVC decoder for the enhancement layer.
A new Dolby Vision device that chooses not to instantiate a second HEVC decoder and supports
profile 4 must distinguish the original profile 4 bitstream from the profile 4 MEL bitstream. When
receiving an original profile 4 bitstream, such a device:
• Exits the Dolby Vision video pipeline
• Uses its normal video pipeline for video processing, and displays a standard dynamic range video
signal only
• Does not display the Dolby Vision logo
So follow me:
Code: Select all
Single Track Dual Layer dvhe.04.06 (BL + EL + RPU)
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My device receives a Dolby Vision
Track whith a Base Layer and a Full ------------- My device is able to decode a profile 4 MEL bitstream
enhancement Layer (FEL) without instantiating a secondary HEVC decoder but is ------------- Exits the Dolby Vision video pipeline,
| receiving a FEL bitstream NO Dolby Vision logo, SDR
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My device can initiate a secondary HEVC decoder
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Dolby Vision (Full enhanced)
My files (dvhe.04) are slightly out of standard: the EL layer should be represented by a HEVC main10 level 4.1 stream instead the one present in the Bluray disk is a High Tier level 5.1.
On some devices, the file may start (with its Dolby Vision Logo) but the file would not be reproduced because the decoder buffer would quickly become saturated.
If instead I choose to play my files with the profiles dvhe.05 and dvhe.08 (useful for processing Single Track Single Layer files (BL + RPU)), the hardware decoder will try to process the Base Layer (BL) and to improve it through RPU metadata by discarding the EL layer.
however, the Base Layer is non-standard (it has a different color space than the IPTPQc2/IPT one) as extracted from a Bluray disk.
It should appear better than an HDR stream (since metadata is dynamic and non-static) but will not reach its maximum splendor due to the lack of data contained in the EL layer.
The lack of this information, however, could lead, in some cases, to evident chromatic aberrations.
