Basis for level_idc calculation

[bradh]

I'm looking to add still imagery EVC support to libheif. Its a little tricky without any sample data to test against, so I'm scratching around to get some parts, then trying to validate those.

In looking at the evcC box written by ffmpeg, I'm seeing this:

0000:4CA0 |                                           00 00 00 |              ...
0000:4CB0 | 3D 65 76 63  43 01 00 D7  00 00 00 00  00 00 00 00 | =evcC..×........
0000:4CC0 | 52 01 40 00  F0 03 02 98  00 01 00 15  32 00 80 6B | R.@.ð.......2..k
0000:4CD0 | 80 00 00 00  00 00 00 00  20 0A 08 0F  16 C0 00 54 | ........ ....À.T
0000:4CE0 | 00 99 00 01  00 04 34 00  FB                       | ......4.û       

The D7 value for level_idc is confusing me though.

If I'm following the spec, it should be 30 times the level value from ISO/IEC 23094-1 Table A.1

D7 is 215.

The highest level in Table A.1 is 6.2. That only works out to 186.

For this file, ffmpeg says:

  Stream #0:0[0x1](und): Video: evc (Baseline) (evc1 / 0x31637665), none(progressive), 320x240, 5 kb/s, SAR 1:1 DAR 4:3, 25 fps, 25 tbr, 12800 tbn (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
      encoder         : Lavc61.22.100 libxeve

So I don't think anything like Level 6.2 would apply in any case.

It doesn't look like that is actually being calculated in ffmpeg, so I guess its coming from libxeve.

Any suggestions for how to debug this?