Hdr metadata

[cool advertise]

Hi, I hope among you there is someone who has enough knowledge to answer me.
The question is simple, but I don't know the answer.
When in a 4k bluray, the main movie is in a single m2ts file, creating a UNTOUCHED version, muxing the track with mkvtoolnix, the hdr metadata viewable with mediainfo remains unchanged, and therefore you can insert in x265 encoder for the eventual encoding , whether the source is the bluray 4k, whether the source is the UNTOUCHED.mkv version.
The problem arises when in the 4k bluray, the main video is split into multiple m2ts files.
Each of them shows different hdr metadata in mediainfo, and by creating the UNTOUCHED.mkv version muxed with mkvtoolnix, it will display the metadata of the first .m2ts bluray playlist file.
I take as an example the bluray 4k, Alita - Battle Angel.
The main movie is in the playlist:
00800.mpls
which in turn contains 4 m2ts files (as reported by the BDInfo tool):
00687.m2ts (00:00:35)
00688.m2ts (01:55:51)
00674.m2ts (00:02:01)
00689.m2ts (00:03:28)

The hdr metadata shown by mediainfo (for the file Alita - Battle Angel [UNTOUCHED].mkv) currently shows the hdr parameters of the first of the four sequential files (00687.m2ts), which would be the initial credits, namely:

Primary colors: BT.2020
Transfer characteristics: PQ
Matrix coefficients: BT.2020 non-constant
MasteringDisplay_ColorPrimaries: Display P3
MasteringDisplay_Luminance: min: 0.0001 cd / m2, max: 1000 cd / m2
MaxCLL: 233 cd / m2
MaxFALL: 63 cd / m2

These instead are the metadata of the 4 m2ts tracks:

General
Complete name                            : E:\Alita - Angelo Della Battaglia [2019] [BLURAY FULL 4K]\BDMV\PLAYLIST\00800.mpls
Format                                   : Blu-ray Playlist
File size                                : 3.81 KiB
Duration                                 : 2 h 1 min
Overall bit rate mode                    : Variable
Overall bit rate                         : 4 b/s

Video #1
ID                                       : 4113 (0x1011)
Menu ID                                  : 1 (0x1)
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2094 App 4, Version 1, HDR10+ Profile A compatible
Codec ID                                 : 36
Duration                                 : 35 s 952 ms
Width                                    : 3 840 pixels
Height                                   : 2 160 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 23.976 (24000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0 (Type 2)
Bit depth                                : 10 bits
Color range                              : Limited
Color primaries                          : BT.2020
Transfer characteristics                 : PQ
Matrix coefficients                      : BT.2020 non-constant
Mastering display color primaries        : Display P3
Mastering display luminance              : min: 0.0001 cd/m2, max: 1000 cd/m2
Maximum Content Light Level              : 233 cd/m2
Maximum Frame-Average Light Level        : 63 cd/m2
format_identifier                        : HDMV
Source                                   : 00687.m2ts

Video #3
ID                                       : 4113 (0x1011)
Menu ID                                  : 1 (0x1)
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2094 App 4, Version 1, HDR10+ Profile A compatible
Codec ID                                 : 36
Duration                                 : 1 h 55 min
Width                                    : 3 840 pixels
Height                                   : 2 160 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 23.976 (24000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0 (Type 2)
Bit depth                                : 10 bits
Color range                              : Limited
Color primaries                          : BT.2020
Transfer characteristics                 : PQ
Matrix coefficients                      : BT.2020 non-constant
Mastering display color primaries        : Display P3
Mastering display luminance              : min: 0.0001 cd/m2, max: 1000 cd/m2
Maximum Content Light Level              : 737 cd/m2
Maximum Frame-Average Light Level        : 130 cd/m2
format_identifier                        : HDMV
Source                                   : 00688.m2ts

Video #5
ID                                       : 4113 (0x1011)
Menu ID                                  : 1 (0x1)
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2094 App 4, Version 1, HDR10+ Profile A compatible
Codec ID                                 : 36
Duration                                 : 2 min 1 s
Width                                    : 3 840 pixels
Height                                   : 2 160 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 23.976 (24000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0 (Type 2)
Bit depth                                : 10 bits
Color range                              : Limited
Color primaries                          : BT.2020
Transfer characteristics                 : PQ
Matrix coefficients                      : BT.2020 non-constant
Mastering display color primaries        : Display P3
Mastering display luminance              : min: 0.0001 cd/m2, max: 1000 cd/m2
Maximum Content Light Level              : 1000 cd/m2
Maximum Frame-Average Light Level        : 18 cd/m2
format_identifier                        : HDMV
Source                                   : 00674.m2ts

Video #7
ID                                       : 4113 (0x1011)
Menu ID                                  : 1 (0x1)
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2094 App 4, Version 1, HDR10+ Profile A compatible
Codec ID                                 : 36
Duration                                 : 3 min 28 s
Width                                    : 3 840 pixels
Height                                   : 2 160 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 23.976 (24000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0 (Type 2)
Bit depth                                : 10 bits
Color range                              : Limited
Color primaries                          : BT.2020
Transfer characteristics                 : PQ
Matrix coefficients                      : BT.2020 non-constant
Mastering display color primaries        : Display P3
Mastering display luminance              : min: 0.0001 cd/m2, max: 1000 cd/m2
Maximum Content Light Level              : 505 cd/m2
Maximum Frame-Average Light Level        : 13 cd/m2
format_identifier                        : HDMV
Source                                   : 00689.m2ts

In the Italian forums, users who are involved in ripping 4k movies with x265 have used the hdr metadata of the track 00688.m2ts, for the rip of the film Alita - Battle Angel.
I suppose there must be a rule, in x265 to determine the correct HDR parameters to use, (including MaxCLL and MaxFALL values), to be included in the x265 encoder, when the bluray 4k movie is splitted in more m2ts files.

So, after having exposed the problem, and having examined a specific case, the question is rather short and simple:
1) Which rule must be applied? (question valid for all bluray movies splitted into multiple m2ts files)
2) In the case of the movie Alita - Battle Angel, which HDR metadata should be used?

[Nico8583]

Have you tried to extract metadata with hdr10plus_parser ? It seems to be a HDR10+ movie.

[cool advertise]

Originally Posted by Nico8583

Have you tried to extract metadata with hdr10plus_parser ? It seems to be a HDR10+ movie.

No. It (Alita - Battle Angel) contains HDR10, HDR10+, and Dolby Vision metadata, but i just want to uses HDR10, so i don't need that tool (hdr10plus_parser).

[sneaker_ger]

The only things that change are MaxCLL and MaxFALL? Wouldn't it make sense to choose the highest MaxCLL and the highest MaxFALL for the complete recode, then? Maybe I'm thinking too simple ...

[cool advertise]

Originally Posted by sneaker_ger

The only things that change are MaxCLL and MinCLL? Wouldn't it make sense to choose the lowest MinCLL and the highest MaxCLL for the complete recode, then? Maybe I'm thinking too simple ...

I also thought almost the same thing.
I have used this metadata for Alita - Battle Angel rip, like other Italian users who have ripped the film:

Color primaries                          : BT.2020
Transfer characteristics                 : PQ
Matrix coefficients                      : BT.2020 non-constant
Mastering display color primaries        : Display P3
Mastering display luminance              : min: 0.0001 cd/m2, max: 1000 cd/m2
Maximum Content Light Level              : 737 cd/m2
Maximum Frame-Average Light Level        : 130 cd/m2

I said I thought like you;
I thought maybe you should choose the maximum value between the various tracks for:
Maximum Content Light Level
and for
Maximum Frame-Average Light Level
so in the case of Alita - Battle Angel I thought you have to choose these:

Color primaries                          : BT.2020
Transfer characteristics                 : PQ
Matrix coefficients                      : BT.2020 non-constant
Mastering display color primaries        : Display P3
Mastering display luminance              : min: 0.0001 cd/m2, max: 1000 cd/m2
Maximum Content Light Level              : 1000 cd/m2
Maximum Frame-Average Light Level        : 130 cd/m2

(and besides if the values to use are different from that of the first track, it means that a software between mediainfo or mkvtoolnix is buggy ..., because the untouched version reports those and should not do it)

but I'm waiting for a more expert answer.

[Nico8583]

Have you tried to create a MKV for each M2TS ? Does any MKV keeps its own metadata ?
And what about if you merge all MKV into one ?

[benwaggoner]

Originally Posted by sneaker_ger

The only things that change are MaxCLL and MaxFALL? Wouldn't it make sense to choose the highest MaxCLL and the highest MaxFALL for the complete recode, then? Maybe I'm thinking too simple ...

That is, in fact, exactly what you need to do. MaxCLL is the brightest pixel in the whole title, and MaxFALL is the brightness of the single brightest frame.

They are not particularly useful values, since one stray pixel or frame can throw off values for a whole movie. Many displays just ignore the metadata for that reason. Dynamic metadata like Dolby Vision and HDR10+ are a lot more useful in practice.

[Zenitram]

Originally Posted by Nico8583

Does any MKV keeps its own metadata ?

No, that is the issue: it is in the stream only; and HDR10 says that a stream should have a constant value; so from MediaInfo developer (me) point of view, it is not worth it to scan the entire stream just for checking that the stream is conform to HDR10 specs else show the maximum value.
Technically not the most difficult in MediaInfo, just need to load in memory the whole file for a very corner case.

[cool advertise]

Originally Posted by Nico8583

Have you tried to create a MKV for each M2TS ? Does any MKV keeps its own metadata ?

To me it turns out that every mkv, keeps its own metadata; strange, I don't understand.
Here is the mediainfo log, for the 4 mkv files created by the respective m2ts files:

General
Unique ID                                : 120006851769432838627067574519937895675 (0x5A487A9B834FD93AA576FDC80A700CFB)
Complete name                            : E:\Alita - Angelo Della Battaglia [2019] [BLURAY FULL 4K]\00687.mkv
Format                                   : Matroska
Format version                           : Version 4
File size                                : 167 MiB
Duration                                 : 35 s 972 ms
Overall bit rate mode                    : Variable
Overall bit rate                         : 38.9 Mb/s
Encoded date                             : UTC 2019-09-10 17:15:48
Writing application                      : mkvmerge v37.0.0 ('Leave It') 64-bit
Writing library                          : libebml v1.3.9 + libmatroska v1.5.2

Video #1
ID                                       : 1
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2094 App 4, Version 1, HDR10+ Profile A compatible
Codec ID                                 : V_MPEGH/ISO/HEVC
Duration                                 : 35 s 953 ms
Bit rate                                 : 22.2 Mb/s
Width                                    : 3 840 pixels
Height                                   : 2 160 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 23.976 (24000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0 (Type 2)
Bit depth                                : 10 bits
Bits/(Pixel*Frame)                       : 0.112
Stream size                              : 95.3 MiB (57%)
Default                                  : Yes
Forced                                   : No
Color range                              : Limited
Color primaries                          : BT.2020
Transfer characteristics                 : PQ
Matrix coefficients                      : BT.2020 non-constant
Mastering display color primaries        : Display P3
Mastering display luminance              : min: 0.0001 cd/m2, max: 1000 cd/m2
Maximum Content Light Level              : 233 cd/m2
Maximum Frame-Average Light Level        : 63 cd/m2

-------------------------------------
General
Unique ID                                : 205024178831424440420367255297167339904 (0x9A3E3874E1E7288AF3B7307CBC9A3180)
Complete name                            : E:\Alita - Angelo Della Battaglia [2019] [BLURAY FULL 4K]\00688.mkv
Format                                   : Matroska
Format version                           : Version 4
File size                                : 49.0 GiB
Duration                                 : 1 h 55 min
Overall bit rate mode                    : Variable
Overall bit rate                         : 60.5 Mb/s
Encoded date                             : UTC 2019-09-10 17:22:40
Writing application                      : mkvmerge v37.0.0 ('Leave It') 64-bit
Writing library                          : libebml v1.3.9 + libmatroska v1.5.2

Video #1
ID                                       : 1
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2094 App 4, Version 1, HDR10+ Profile A compatible
Codec ID                                 : V_MPEGH/ISO/HEVC
Duration                                 : 1 h 55 min
Bit rate                                 : 42.7 Mb/s
Width                                    : 3 840 pixels
Height                                   : 2 160 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 23.976 (24000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0 (Type 2)
Bit depth                                : 10 bits
Bits/(Pixel*Frame)                       : 0.214
Stream size                              : 34.5 GiB (70%)
Default                                  : Yes
Forced                                   : No
Color range                              : Limited
Color primaries                          : BT.2020
Transfer characteristics                 : PQ
Matrix coefficients                      : BT.2020 non-constant
Mastering display color primaries        : Display P3
Mastering display luminance              : min: 0.0001 cd/m2, max: 1000 cd/m2
Maximum Content Light Level              : 737 cd/m2
Maximum Frame-Average Light Level        : 130 cd/m2
-------------------------
General
Unique ID                                : 198987914817856560951365290631281396266 (0x95B3ADA9C7B448504B5B8D57DFCA4A2A)
Complete name                            : E:\Alita - Angelo Della Battaglia [2019] [BLURAY FULL 4K]\00674.mkv
Format                                   : Matroska
Format version                           : Version 4
File size                                : 410 MiB
Duration                                 : 2 min 1 s
Overall bit rate mode                    : Variable
Overall bit rate                         : 28.3 Mb/s
Encoded date                             : UTC 2019-09-10 18:12:33
Writing application                      : mkvmerge v37.0.0 ('Leave It') 64-bit
Writing library                          : libebml v1.3.9 + libmatroska v1.5.2

Video #1
ID                                       : 1
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2094 App 4, Version 1, HDR10+ Profile A compatible
Codec ID                                 : V_MPEGH/ISO/HEVC
Duration                                 : 2 min 1 s
Bit rate                                 : 10.2 Mb/s
Width                                    : 3 840 pixels
Height                                   : 2 160 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 23.976 (24000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0 (Type 2)
Bit depth                                : 10 bits
Bits/(Pixel*Frame)                       : 0.051
Stream size                              : 148 MiB (36%)
Default                                  : Yes
Forced                                   : No
Color range                              : Limited
Color primaries                          : BT.2020
Transfer characteristics                 : PQ
Matrix coefficients                      : BT.2020 non-constant
Mastering display color primaries        : Display P3
Mastering display luminance              : min: 0.0001 cd/m2, max: 1000 cd/m2
Maximum Content Light Level              : 1000 cd/m2
Maximum Frame-Average Light Level        : 18 cd/m2
-----------------------------------
General
Unique ID                                : 122103663906236629347105964736554171473 (0x5BDC4F6D7021D4BDF4CC6DFCF0B37C51)
Complete name                            : E:\Alita - Angelo Della Battaglia [2019] [BLURAY FULL 4K]\00689.mkv
Format                                   : Matroska
Format version                           : Version 4
File size                                : 924 MiB
Duration                                 : 3 min 28 s
Overall bit rate mode                    : Variable
Overall bit rate                         : 37.1 Mb/s
Encoded date                             : UTC 2019-09-10 18:13:30
Writing application                      : mkvmerge v37.0.0 ('Leave It') 64-bit
Writing library                          : libebml v1.3.9 + libmatroska v1.5.2

Video #1
ID                                       : 1
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2094 App 4, Version 1, HDR10+ Profile A compatible
Codec ID                                 : V_MPEGH/ISO/HEVC
Duration                                 : 3 min 28 s
Bit rate                                 : 19.7 Mb/s
Width                                    : 3 840 pixels
Height                                   : 2 160 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 23.976 (24000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0 (Type 2)
Bit depth                                : 10 bits
Bits/(Pixel*Frame)                       : 0.099
Stream size                              : 489 MiB (53%)
Default                                  : Yes
Forced                                   : No
Color range                              : Limited
Color primaries                          : BT.2020
Transfer characteristics                 : PQ
Matrix coefficients                      : BT.2020 non-constant
Mastering display color primaries        : Display P3
Mastering display luminance              : min: 0.0001 cd/m2, max: 1000 cd/m2
Maximum Content Light Level              : 505 cd/m2
Maximum Frame-Average Light Level        : 13 cd/m2

And what about if you merge all MKV into one ?
I'm still muxing it with mkvtoolnix...i will answer soon

[Nico8583]

I think the result will be the same, I think it will take the metadata from the first MKV but I'm waiting your result.
If the result is the same, perhaps you could try to open a ticket to mkvtoolnix.

[cool advertise]

Originally Posted by Nico8583

And what about if you merge all MKV into one ?

It take metadata from first mkv file or from first m2ts file.
Here is the mediainfo log:

General
Unique ID                                : 206388322543053743391594044095595016496 (0x9B44F1EF2C7B0BC2FED886B1DBF7F130)
Complete name                            : E:\Alita - Angelo Della Battaglia [2019] [BLURAY FULL 4K]\Alita - Angelo Della Battaglia [2019] [UNTOUCHED FROM MERGED MKV].mkv
Format                                   : Matroska
Format version                           : Version 4
File size                                : 50.5 GiB
Duration                                 : 2 h 1 min
Overall bit rate mode                    : Variable
Overall bit rate                         : 59.2 Mb/s
Encoded date                             : UTC 2019-09-10 18:22:43
Writing application                      : mkvmerge v37.0.0 ('Leave It') 64-bit
Writing library                          : libebml v1.3.9 + libmatroska v1.5.2

Video #1
ID                                       : 1
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2094 App 4, Version 1, HDR10+ Profile A compatible
Codec ID                                 : V_MPEGH/ISO/HEVC
Duration                                 : 2 h 1 min
Bit rate                                 : 41.4 Mb/s
Width                                    : 3 840 pixels
Height                                   : 2 160 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 23.976 (24000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0 (Type 2)
Bit depth                                : 10 bits
Bits/(Pixel*Frame)                       : 0.208
Stream size                              : 35.2 GiB (70%)
Default                                  : Yes
Forced                                   : No
Color range                              : Limited
Color primaries                          : BT.2020
Transfer characteristics                 : PQ
Matrix coefficients                      : BT.2020 non-constant
Mastering display color primaries        : Display P3
Mastering display luminance              : min: 0.0001 cd/m2, max: 1000 cd/m2
Maximum Content Light Level              : 233 cd/m2
Maximum Frame-Average Light Level        : 63 cd/m2

[Nico8583]

Originally Posted by Zenitram

No, that is the issue: it is in the stream only; and HDR10 says that a stream should have a constant value; so from MediaInfo developer (me) point of view, it is not worth it to scan the entire stream just for checking that the stream is conform to HDR10 specs else show the maximum value.
Technically not the most difficult in MediaInfo, just need to load in memory the whole file for a very corner case.

No problem, I think the job should be do by the muxer, this is why I asked to cool advertise to try it
When the muxer does the job, it could analyze the max values for each M2TS and keep the higher values as default value ?!
But the values will be wrong for 3 or all M2TS segments, so is it useful to use that when encoding to x265 ?

[cool advertise]

Thanks to all those who participated in the discussion, and a special thanks to "benwaggoner" for the precious answer.

[cool advertise]

Originally Posted by Nico8583

No problem, I think the job should be do by the muxer, this is why I asked to cool advertise to try it
When the muxer does the job, it could analyze the max values for each M2TS and keep the higher values as default value ?!
But the values will be wrong for 3 or all M2TS segments, so is it useful to use that when encoding to x265 ?

I opened a issue on gitlab, to the mkvtoolnix developer Moritz Bunkus, proposing to read this discussion and provide an opinion.
Here is his answer:

Metadata such as pixel dimensions or HDR metadata can change mid-stream. That's simply a limitation, same as in MPEG transport streams (e.g. when content in a DVB stream changes between HD and SD content, which is where pixel dimensions change, or even between different shows, where encoder setting change). Players just have to cope with that — and they already do. A Blu-ray player reading a playlist of multiple M2TS already has to deal with changing HDR metadata between the different M2TS files, for example, and for other content VLC, MPC-HC and all the other players can already deal with changing pixel dimensions within the same stream.
About modifying HDR metadata during muxing: that's not MKVToolNix' job, nor is it in the scope of this project (it's not a video mastering application). It would only be possible for certain metadata values anyway (the Max* values, for examples), but not for others.
No bug here.

With this I don't want to go into the subject further.

[benwaggoner]

Yes, since the metadata is contained in every IDR, it can change frequently. I believe the Blu-ray spec doesn't allow for the static metadata to change during the main title, but that's not something that is or could be technically enforced.

How a display deals with unexpectedly changing static metadata is another question entirely. I wouldn't be surprised to see some pathological behavior in some.

[Nico8583]

So you think the better way is to keep the higher values of all M2TS ? Or keep the values from the M2TS with the longer duration ? Thank you.

[benwaggoner]

Originally Posted by Nico8583

So you think the better way is to keep the higher values of all M2TS ? Or keep the values from the M2TS with the longer duration ? Thank you.

The safest thing is to use the highest value of all of them. However, I would expect that the main title would have the same value in all its M2TS files, so this might be a way to discriminate between main title and extras.

[Blue_MiSfit]

This is pretty clearly dealing with pirated content, so I have to make note of rule 6 here...