Improve colours in Dolby Vision samples

[cehoyos]

The Dolby Vision samples show strange colours:
​https://4kmedia.org/lg-amaze-dolby-vision-uhd-4k-demo/

$ ffmpeg -i LG\ Amaze\ Dolby\ Vision\ UHD\ 4K\ Demo.ts -qscale 2 out.avi
ffmpeg version N-92729-ga1f0dd2 Copyright (c) 2000-2018 the FFmpeg developers
  built with gcc 6.4.0 (GCC)
  configuration: --enable-gpl --enable-libxml2 --enable-gnutls --enable-gmp --enable-version3 --enable-libx264
  libavutil      56. 24.101 / 56. 24.101
  libavcodec     58. 42.102 / 58. 42.102
  libavformat    58. 24.101 / 58. 24.101
  libavdevice    58.  6.101 / 58.  6.101
  libavfilter     7. 46.101 /  7. 46.101
  libswscale      5.  4.100 /  5.  4.100
  libswresample   3.  4.100 /  3.  4.100
  libpostproc    55.  4.100 / 55.  4.100
[hevc @ 0x283a800] Skipping NAL unit 62
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'LG Amaze Dolby Vision UHD 4K Demo.ts':
  Metadata:
    major_brand     : mp42
    minor_version   : 1
    compatible_brands: mp42dby1isom
    creation_time   : 2017-04-13T20:09:18.000000Z
  Duration: 00:00:56.20, start: 0.000000, bitrate: 28362 kb/s
    Stream #0:0(und): Video: hevc (Main 10) (dvhe / 0x65687664), yuv420p10le(tv), 3840x2160 [SAR 1:1 DAR 16:9], 27713 kb/s, 60 fps, 60 tbr, 60k tbn, 60 tbc (default)
    Metadata:
      creation_time   : 2017-04-13T20:09:18.000000Z
      handler_name    : video handler
      encoder         : DOVI Coding
    Stream #0:1(und): Audio: eac3 (ec-3 / 0x332D6365), 48000 Hz, 5.1(side), fltp, 640 kb/s (default)
    Metadata:
      creation_time   : 2017-04-13T20:09:18.000000Z
      handler_name    : sound handler
    Side data:
      audio service type: main
Please use -q:a or -q:v, -qscale is ambiguous
Stream mapping:
  Stream #0:0 -> #0:0 (hevc (native) -> mpeg4 (native))
  Stream #0:1 -> #0:1 (eac3 (native) -> ac3 (native))
Press [q] to stop, [?] for help
[hevc @ 0x286df00] Skipping NAL unit 62
[hevc @ 0x2868100] Skipping NAL unit 62
[hevc @ 0x287d0c0] Skipping NAL unit 62
[hevc @ 0x28cdf80] Skipping NAL unit 62
[hevc @ 0x28de740] Skipping NAL unit 62
[hevc @ 0x2945bc0] Skipping NAL unit 62
[hevc @ 0x29562c0] Skipping NAL unit 62
[hevc @ 0x2977440] Skipping NAL unit 62
[hevc @ 0x2966ac0] Skipping NAL unit 62
[hevc @ 0x286df00] Skipping NAL unit 62
[hevc @ 0x2868100] Skipping NAL unit 62
Output #0, avi, to 'out.avi':
  Metadata:
    major_brand     : mp42
    minor_version   : 1
    compatible_brands: mp42dby1isom
    ISFT            : Lavf58.24.101
    Stream #0:0(und): Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 3840x2160 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 60 fps, 60 tbn, 60 tbc (default)
    Metadata:
      creation_time   : 2017-04-13T20:09:18.000000Z
      handler_name    : video handler
      encoder         : Lavc58.42.102 mpeg4
    Side data:
      cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1
    Stream #0:1(und): Audio: ac3 ([0] [0][0] / 0x2000), 48000 Hz, 5.1(side), fltp, 448 kb/s (default)
    Metadata:
      creation_time   : 2017-04-13T20:09:18.000000Z
      handler_name    : sound handler
      encoder         : Lavc58.42.102 ac3
    Side data:
      audio service type: main
[hevc @ 0x287d0c0] Skipping NAL unit 62
[hevc @ 0x28cdf80] Skipping NAL unit 62

...

[hevc @ 0x28de740] Skipping NAL unit 62
[hevc @ 0x2945bc0] Skipping NAL unit 62
frame= 3372 fps= 31 q=2.0 Lsize= 1769927kB time=00:00:56.20 bitrate=257993.6kbits/s speed=0.51x
video:1766724kB audio:3073kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.007307%

[JEEB]

The colorspace is supposed to be Dolby's skewed ICtCp + BT.2020 + PQ.

This is why I noted that adding the identifiers lets you demux and decode, but not present.

[Balling]

See ​https://github.com/sekrit-twc/zimg/issues/69#issuecomment-552184393
I suppose we just wrongly think it is BT.2020 color. (Or maybe ITP color of Dolby is a little bit different from that of BT.2100 ICtCp.)

[Balling]

I just wanted to add another example (besides ​https://drive.google.com/file/d/1aP276spsqW-EbIIVrzdI9mwTYO87d0ac/view?usp=sharing) which is simpler and which though should be right!
I also added issue ​https://github.com/sekrit-twc/zimg/issues/117 so maybe this will be finally solved and we will be more close to whole HDR10+ / Dolby Vision / Dolby Atmos decoding!