Is HDR to SDR Conversion for non HDR Displays working correctly?

It works in the 4.9 kernel – of which test builds can be found on this forum

Sam

I just tried quite a few HDR mkv’s on my 4.9 test Vero to see if SDR conversion has improved, and my overall impression is that it has. I checked that every title was on 50% contrast/brightness in Kodi, and almost all of them looked excellent. On my 3.14 Vero almost every title needs a contrast boost. Still found a couple of titles that seemed rather flat on 4.9, but it looks like progress is being made.

Out of interest, do those titles have metadata, and can you see anything in that which differs from titles which are ‘excellent’?

I would need some guidance on how to obtain the metadata you might be interested in, happy to help if I can.

Mediainfo should do it. Just post the output here.

I can’t spot an exact association between the mediainfo details and my perception of the SDR conversion, but I’m not familiar with this metadata, I notice that some titles have a couple additional attributes reported but it’s not consistent.

Here is The Dark Knight (looks a bit flat)

Video
ID                                       : 1
ID in the original source medium         : 4113 (0x1011)
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2086, HDR10 compatible
Codec ID                                 : V_MPEGH/ISO/HEVC
Duration                                 : 2 h 32 min
Bit rate                                 : 47.2 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)                       : 0.237
Stream size                              : 50.1 GiB (92%)
Language                                 : English
Default                                  : No
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: 0.0050 cd/m2, max: 4000 cd/m2
Maximum Content Light Level              : 500 cd/m2
Maximum Frame-Average Light Level        : 200 cd/m2
Original source medium                   : Blu-ray

Here is Star Trek 2009 (also looks a bit flat)

Video
ID                                       : 1
ID in the original source medium         : 4113 (0x1011)
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2086, HDR10 compatible
Codec ID                                 : V_MPEGH/ISO/HEVC
Duration                                 : 2 h 6 min
Bit rate                                 : 53.0 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)                       : 0.267
Stream size                              : 47.0 GiB (91%)
Writing library                          : ATEME Titan KFE 3.7.3 (4.7.3.1003)
Language                                 : English
Default                                  : No
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: 0.0050 cd/m2, max: 1000 cd/m2
Original source medium                   : Blu-ray

Here is Blade Runner 2049 (looks flat)

Video
ID                                       : 1
ID in the original source medium         : 4113 (0x1011)
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2086, HDR10 compatible
Codec ID                                 : V_MPEGH/ISO/HEVC
Duration                                 : 2 h 43 min
Bit rate                                 : 49.5 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)                       : 0.249
Stream size                              : 56.5 GiB (91%)
Language                                 : English
Default                                  : No
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: 0.0050 cd/m2, max: 4000 cd/m2
Maximum Content Light Level              : 457 cd/m2
Maximum Frame-Average Light Level        : 179 cd/m2
Original source medium                   : Blu-ray

Here is Gladiator (looks good)

Video
ID                                       : 1
ID in the original source medium         : 4113 (0x1011)
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2086, HDR10 compatible
Codec ID                                 : V_MPEGH/ISO/HEVC
Duration                                 : 2 h 50 min
Bit rate                                 : 43.3 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)                       : 0.218
Stream size                              : 51.7 GiB (92%)
Language                                 : English
Default                                  : No
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: 0.0050 cd/m2, max: 1000 cd/m2
Maximum Content Light Level              : 1000 cd/m2
Maximum Frame-Average Light Level        : 497 cd/m2
Original source medium                   : Blu-ray

Toy Story (perfect)

Video
ID                                       : 1
ID in the original source medium         : 4113 (0x1011)
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2086, HDR10 compatible
Codec ID                                 : V_MPEGH/ISO/HEVC
Duration                                 : 1 h 21 min
Bit rate                                 : 58.1 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)                       : 0.292
Stream size                              : 32.9 GiB (88%)
Writing library                          : ATEME Titan File 3.9.0 (4.9.0.0)        
Language                                 : English
Default                                  : No
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: 0.0000 cd/m2, max: 1000 cd/m2
Original source medium                   : Blu-ray

Just one more, The Dark Knight Rises (excellent). All titles I refer to I am benchmarking against the regular blu-ray mkv’s.

Video
ID                                       : 1
ID in the original source medium         : 4113 (0x1011)
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2086, HDR10 compatible
Codec ID                                 : V_MPEGH/ISO/HEVC
Duration                                 : 2 h 44 min
Bit rate                                 : 55.8 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)                       : 0.281
Stream size                              : 64.1 GiB (93%)
Language                                 : English
Default                                  : No
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: 0.0050 cd/m2, max: 4000 cd/m2
Maximum Content Light Level              : 500 cd/m2
Maximum Frame-Average Light Level        : 200 cd/m2
Original source medium                   : Blu-ray

Many thanks. The only values vero cares about are Maximum display luminance and Maximum content light level, but I can’t see any pattern there.

Out of interest, do you know the (measured or specified) maximum luminance your display is capable of?

Another useful datapoint would be whether these vids play ‘perfectly’ from blu-ray or on your TV’s internal player (if it has one). No-one is saying blu-ray makers or whoever rips them always get it right!

My main system’s TV is an old Panny plasma, so its max luminance will be whatever is typical of a plasma circa 2010.

I managed to get my Panny UHD player to connect to my NAS (have to enable SMBv1 for it to work). Panny mkv support is very primitive, 24p is force converted to 60Hz, no hi-res audio support, no chapter point support. However, I would say the HDR->SDR conversion is very similar to the 4.9 Vero. The titles that look a bit flat on the Vero also tend to look flat on the Panny. So perhaps this is a mastering/authoring issue.

I experimented with my TV picture modes. It’s been running in THX for a while, that seems to lock out any user-adjustment of the gamma value. I switched to a user-adjustable mode, and the default value of 2.2 needs to be reduced to 2.0 or 1.8 on the titles that are looking too subdued, and this brings them to life and they then look very good. I will see if this ends up “over-cooking” the other titles that already looked good. If this was adjustable in Kodi that would be neat, as it would then be title-specific. I suppose I can already get some way there by adjusting Kodi contrast, but the end result is not quite as good.

Also I use to Vero 4k, and find HDR movies very dark on my non HDR (SDR) 4K TV.

I use Plex addon, but that shouldn’t do anything I guess.

Where can I find a release with the new kernel to install on the Vero? Also, will I be able to go back to stable later?

Thanks.

Edit: found this [TESTING] Linux 4.9 kernel and improved video stack for Vero 4K / 4K +

/Söder

1 Like

I just went back and forth between 3.14 and 4.9 Vero’s and the SDR conversion on 4.9 is definitely better. 4.9 is still perhaps just a touch conservative with a slight dark shift compared to blu-ray equivalents, this is more noticeable on some titles than others.

Although 4.9 still has some problems, just looked at Toy Story 2, sourced from a direct UHD disc-to-mkv import, and it is almost unwatchably bad, like I’m watching the film through sunglasses, yet the mediainfo is nothing out of the ordinary? Toy Story 1 is fine.

Video
ID                                       : 1
ID in the original source medium         : 4113 (0x1011)
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5.1@High
HDR format                               : SMPTE ST 2086, HDR10 compatible
Codec ID                                 : V_MPEGH/ISO/HEVC
Duration                                 : 1 h 32 min
Bit rate                                 : 50.6 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)                       : 0.255
Stream size                              : 32.7 GiB (88%)
Writing library                          : ATEME Titan File 3.9.0 (4.9.0.0)        
Language                                 : English
Default                                  : No
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: 0.0000 cd/m2, max: 1000 cd/m2
Original source medium                   : Blu-ray

Any update on HDR to SDR tone mapping?

There is progress - indeed light at the end of the tunnel. But still work to do on what options to present to users.

What I have found is there is no such thing as ‘correct’ HDR-SDR conversion (otherwise, we wouldn’t need HDR10+ and Dolby, would we?) Also the curve we have in the 4.9 kernel is actually difficult to improve on for the test clips I’ve been using on a 100-nit screen.

If you have a Vero, what is your experience with the current implementation, and on what display?

I haven’t tried installing 4.9 kernel so I’m not sure yet, i have an X30 JVC projector.

It’s extremely dark here on a VT50E plasma. At least the base brightness is not right… But: With my Panasonic UHD player I can specify exactly what the maximum output brightness should be (adjusting the tonemapping curve to end at 350nits and probably applying a nice brightness roll-off). But there’s no need to adust the overall brightness of the converted HDR image when playing it back on a SDR screen.

According to this your VT50 should have a maximum brightness around 100 nits, which is ‘standard’. It also says in THX mode it has a gamma of 2.2 which would be brighter than the 2.4 measured OOTB. Are you using THX mode?

I am using the THX Cinema mode, yes. But what does that have to do with anything?
Dark on Vero means nearly not watchable and brightness has to be adjusted quite significantly :rofl: Whereas playing a UHD disc on my Panasonic UHD player it’s pretty much indistinguishable from a BD without any adjustments, if you don’t know what you’re playing.

All I can say is HDR played on the screen on my desk (100nits) looks fine. I’m trying to understand why it would be different on yours. Have you adjusted it for white and black levels (contrast and brightness)?

Obviously I haven’t as SDR on Vero and all other playback sources look absolutely fine. But I’ve got a sample here you may test with… I’m quite sure it will be way too dark for you as well :slightly_smiling_face: Maybe it’s a bad sample in the end though :man_shrugging:t2: