hi guys this is my first time dealing with a m2ts file. i've read nearly all the topics, similar problems, guides etc. my problem is...

i've demuxed a m2ts video with tsmuxer, i get the video, and preffered ac3 and dts-hd.ma sound files and merged with mkvmerge. but when i play the video with vlc, songs, musics, effects for example the engine sound of car, gun shoot, rain drops etc are perfect but no sounds of peoples dialogs. but:

1-there isn't a problem at mpc-hc.
2-i use a 5.1 sound system at my desktop pc but always useing at stereo mode. when i change the settings at realtek panel from stereo to surround, everything goes normal with vlc. but i have hundreds of videos with dts-hd.ma 7.1, atmos truehd 7.1 and i never had a problem until today. and also i have the same problem with the 2ch ac3 sound.
3-i've tried ripbot and makemkv but nothing changed.
4-most people aviced bdinfo to determine the true m2ts file but i could't use it. i get several scanning errors. so i find manuelly which was not hard to find. there wa just 10 m2ts files and just one of them was 32gb. but i wonder if this might be a problem.

and some questions. at the moment i have just one m2ts video and i have no chance for another tryout. so i wonder...

1-do i really need bdinfo? it can't be so hard to find the true 20-30gb m2ts unless there aren't tens of small pieces.
2-do i have to demux first? what might happen when directly put the m2ts to mkvmerge (actually i did but as i couldn't get a successuful result with normal ways, i can't be sure from that try)