Trimming TrueHD 5.1 audio in .mka by an exact number of samples

[uranometria]

I have a TrueHD 5.1 audio track contained in .mka, and I want to cut a number of samples off the beginning of the track without re-encoding.
A post at http://forum.doom9.org/showthread.php?t=146150 by Austin Forgotten suggests to use a hex editor. But I don't know how to edit the audio file properly in hex editor. Can you please teach me how or suggest another way to accomplish this?

Thanks.

[El Heggunte]

If I were you, I would decompress to PCM (in a WAV container, if below 4GB, or as W64),
trim with an audio editor, save, and then recompress to a lossless format (ALAC, FLAC, MLP, or Pure Lossess DTS-HD —
— MKVtoolnix supports all of these).

[sneaker]

A post at http://forum.doom9.org/showthread.php?t=146150 by Austin Forgotten suggests to use a hex editor.

He doesn't say anything about sample accuracy and I don't think it is possible at all. If you need that kind of accuracy you have to follow El Heggunte's suggestion. If you can live without sample accuracy you can cut using mkvtoolnix (split by parts).