Solved can't play MKV files downloaded from youtube

hello
i'm a student and i frequently download lectures from youtube to watch them later
earlier this month i noticed a change in the extension of the files i download from MP4 to MKV which windows media player can't run
i tried media player classic which played the sound only
VLC played the voice but you can see what's wrong with the video

the strange thing here is my Samsung Note 3 can play it using a 3rd party app called V player but i don't like watching lectures on mobile screen
can you help me with this
thanks in advance

If SPlayer Portable (make sure to get the Portable. It doesn't have some bugs the installed version does) won't play it, you can try to fix it

Meteorite 0.11 beta

and/or convert it

MkvToMp4 0.224

The converter above is very fast especially for batch jobs where you only have to convert the audio and remux.

Also if there is a checksum available such as MD5 for the videos, check the downloaded files to make sure they match(not corrupted by the download process.)

well
i found out that IDM newer versions download videos as MKV with strange encoding which isn't the same encoding that ordinary MKV files use
gone for downloading with a java based downloader keepvid

Reinstall PC media player?