Audio doesn't play on some computers

[MixMastaJames]

I have the weirdest issue. I have some MP4 files that have audio in them, but on some computers, you can't hear it. We've tested it on multiple Windows 10 computers and we've had the same issue. Some of us can hear it, and some of us can't. I've looked at the file and it has audio, I've tried to export it in both Media Encoder and Premiere directly and a few other things but we get the same result. 

Does anyone know what's causing this? Some of the computers have the exact same OS loadset and updates on them, so that makes it even weirder since it works on some but not others. 

Any ideas?

[Peru Bob]

Please use the free MediaInfo and post a screenshot of the properties of your media in tree view:
https://mediaarea.net/en/MediaInfo

[MixMastaJames]

Had to blur the name, but here is the info

[MixMastaJames]

Any ideas?

[MixMastaJames]

Any clue? I posted screen shots showing the audio is there and playing, but won't go through the speakers

https://community.adobe.com/t5/premiere-pro-discussions/audio-doesn-t-play-on-some-computers/m-p/143...

[MixMastaJames]

Can anyone help?

[Bill Sprague]

I google searched for the "mp4a-40-2" audio codec shown in the MediaInfo list and got a lot of hits.  One seems to explain it well enough.  "files with the extension .m4a can contain audio data encoded using Apple's Advanced Lossless Audio Codec (ALAC) which is not widely supported outside the Apple ecosystem and such files will typically fail to play on many media players."

What is the source of the files that won't play?

[MixMastaJames]

 This is the info from the source that the video is being edited from. I get the same problem with this. I can't hear the audio but some can, it looks like a different codec, right? 

[MixMastaJames]

Any ideas on this one? 

[MixMastaJames]

That's not the answer, that's the source video which also doesn't play any sound but has a soundtrack in it. It's not just the exported videos with that codec from the first one, it's these too. 

[Peru Bob]

See if something here helps:

https://answers.microsoft.com/en-us/windows/forum/all/why-does-my-mp4-video-not-play-any-sound/7a6ed...

[MixMastaJames]

Thanks, I did find that and have VLC but it didn't work. Also tried to export the audio from there like a tutorial showed me, but that didn't help either. 

[MixMastaJames]

Anyone have any idea what's happening? I can't be the only one!

[MixMastaJames]

These are the volume meters from Premiere 2023 and my VoiceMeeter. The audio is there and playing, but there is NO sound. How is this even possible? This is playing the source video from Premiere that has the PCM twos Codec.

   

[Averdahl]

These are the volume meters from Premiere 2023 and my VoiceMeeter. The audio is there and playing, but there is NO sound. How is this even possible?    

By @MixMastaJames

From your description it clearly sounds that some of your source audio is out of phase. When audio is out of phase you get exactly what you describe, some devices are silent though the audio meters register that there is audio there. The solution is to make sure that the source files are in phase rather than out of phase. 

Here is an example of what it sounds like and how it visually looks and is great to learn from and understand why it happens: Audio Phase: Why You Need To Pay Attention To This - YouTube

[MixMastaJames]

If this was just on my computer I would get that, but it's different on other computers. Some play the sound, others (like mine) don't. Some of the computers have the exact same loadset on them because they're managed by our IT at work. So it's even more odd that it's doing it there. That's what I don't get about this. 

[Richard M Knight · Accepted solution]

Try using the fill left with right effect on the faulty clips, this will show if you have an out of phase issue.

[MixMastaJames]

ok wow that worked!  So how do these get out of phase? and why is it different on every computer.

[Richard M Knight]

You will find the computers that dont work have their audio monitoring set to mono, this is often the case with laptops or smartphones.

If the audio has two tracks, left and right, with the same audio on both, if one of the tracks is phased reversed when listening in mono the sound will cancel out and you will hear nothing (or very little). If listening in stereo it will sound almost normal.

Often the cause of out of phase sound is using a balanced mono microphone into an unbalanced 3.5mm stereo jack on a camera.

[MixMastaJames]

OK that actually makes sense because I'm deaf in one ear and my computer is set to mono. One of the other guys testing wears a hearing aid, so I bet his was like that too. As weird as it is, this makes sense now. Thanks!