NO AUDIO ON MP4 FILES - VIDEO GOOD

i have both WMP and VLC on my system which i have been using for years.

recently, i discovered that some MP4 files will not play any audio. on sorting through the files, i discovered that files with no Bit rate, channels and audio sample rates under their Properties/Details that did not play.
i downloaded the The latest version of the K-Lite Codec Pack 15.4.4 and did some tweaking to no avail.
i also installed the latest VLC but still not playing such files even on Windows Media Player.

I use Windows 10

Did you also try the MPC-HC player from K-Lite?

If nothing plays the audio, then it is possible that it does not contain any audio track. You can check with the MediaInfo tool that is included with K-Lite.

Yes, I did use the MPC-HC (Nightly, 64) from K-lite.

the files have audio as i use to play the files previously. I checked the mediaInfo but did not know what to look for. it is attached.

I see that the file was downloaded from Youtube. They use separate files for audio and video. I checked the file size for that video and it matches. It is video only.

Maybe you also downloaded the audio file in the past, and have deleted that file.

MPC-HC can play both files at same time if you download both.

i though that too...
so after your advice i did a fresh download, and still the same issue. Videos play but not audio.
looked across many files on my computer and some MP4 are like 5 years old and never moved from their folder, yet they dont play their audio while some do.

If you did a fresh download you probably downloaded the same file again. It contains only video.

Several years ago the MP4 files on Youtube contained both audio and video. They moved to separate files for audio and video later. So some of your files can indeed have audio and some have not.

I use this Firefox addon:
https://addons.mozilla.org/en-US/firefox/addon/youtube_downloader_webx/

nope. the file in youtube contains both audio and video.

i used your add on but mostly for extracting the audio or the video from mp4. what i need is to understand why my system will not play both like it use to play before

That file with a size of 48.1 MB only contains video. That is a fact.

If you install the native client and ffmpeg plugins for that Firefox extension then it will be capable of downloading both the audio and the video files and merge them together into a new MP4 file that contains both.