MKV is a container within which the video may or may not be .m2ts,
As it audio you need to know about you have to check the contained audio stream in the container has the required Atmos Metadata
Download and install the version of Mediainfo for your OS
If windows
Open a file in mediainfo. Select view - Tree - export as text. Open the text in notepad - select all and copy to clipboard, (CRTL +C),
Create a reply here and paste the text (crt + V) and post so we can see what is in the container
General
Unique ID : 204756960649638254555385641663587130930 (0x9A0AC1954107F470A0583032EF3F9E32)
Complete name : C:\Users\sunay\Downloads\Dolby_Atmos_Natures_Fury_1920x1080_ATMOS_71-thedigitaltheater.mkv
Format : Matroska
Format version : Version 2
File size : 336 MiB
Duration : 1 min 51 s
Overall bit rate mode : Variable
Overall bit rate : 25.4 Mb/s
Movie name : Nature's Fury - ATMOS - thedigitaltheater.com
Encoded date : UTC 2019-01-22 15:38:12
Writing application : DVDFab 11.0.1.4
Writing library : libebml v1.3.4 + libmatroska v1.4.5
Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile :
[email protected]
Format settings : CABAC / 4 Ref Frames
Format settings, CABAC : Yes
Format settings, Reference frames : 4 frames
Codec ID : V_MPEG4/ISO/AVC
Duration : 1 min 50 s
Bit rate mode : Variable
Bit rate : 19.1 Mb/s
Maximum bit rate : 30.0 Mb/s
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 24.000 FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.384
Stream size : 252 MiB (75%)
Default : Yes
Forced : No
Color range : Limited
Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.709
Audio
ID : 2
Format : MLP FBA 16-ch
Format/Info : Meridian Lossless Packing FBA with 16-channel presentation
Commercial name : Dolby TrueHD with Dolby Atmos
Codec ID : A_TRUEHD
Duration : 1 min 51 s
Bit rate mode : Variable
Bit rate : 6 320 kb/s
Maximum bit rate : 9 849 kb/s
Channel(s) : 8 channels
Channel layout : L R C LFE Ls Rs Lb Rb
Sampling rate : 48.0 kHz
Frame rate : 1 200.000 FPS (40 SPF)
Compression mode : Lossless
Stream size : 83.8 MiB (25%)
Language : English
Default : Yes
Forced : No
Number of dynamic objects : 15
Bed channel count : 1 channel
Bed channel configuration : LFE
Menu
00:00:00.000 : en
01)00:00:00:000