Audio doesn't play in certain MP4's created on a MAC

[DigitalHarbor]

I have 6 large videos recorded from an online webinar. The person who recorded them uses a Mac. We found that with some of these videos (but not all of them), we had to open them using Quicktime in order to hear any audio. Windows Media Player would play the video fine, but not the audio portion.

I need to edit each of these and I've tried with several programs, but there's no audio so I cannot edit them. I've tried AVS4YOU Video Editor, Video Remaker, and Windows Live Movie Maker. I cannot purchase a full-blown video editor at this time.

How can I open these, hear the audio, edit them, and re-save them? I don't really care what format, but a smaller file would be better. This is making me nuts. Thanks for your help! -Jill

[Cornucopia]

Pretty sure there IS audio.
I'm guessing they're using the ALAC codec, but there's no need to guess. Just post an advanced text readout from MediaInfo. It will tell you exactly which codec(s) is/are being used.
Assuming it is a QT-exclusive codec such as ALAC, you might be able to convert using ffmpeg (you'll need to create a command-line script). Should that not work, or should that appear too complicated, I would suggest paying the $29 for QuickTime Pro (v7.x). It will allow you to export/convert to either your desired end format or at least a decent intermediate format that could be compatible with your existing editing app. Plus, it can also do basic edits on its own.

Scott

[DigitalHarbor]

Thanks, Scott. Yes, there is definitely audio because I can hear it when opened in QuickTime. I will try the ffmpeg suggestion or just suck it up and buy QT Pro.

[DigitalHarbor]

I'm still struggling with WHY these videos are in a format that I cannot work with; I've never encountered this and have worked with video on and off for many years. I'm not sure how to tell if I'll have this problem in the future just by looking at the "MP4" (and assuming I can work with it). If the format/properties of the file at least showed that it was a specific codec, that would help.

[poisondeathray]

As suggested earlier, use mediainfo for more information (view=>text). Determine what is different about the ones that work, vs. the ones that "don't work"

Another option is to use a simple free video editor such as aviutl that can open basically anything (because it uses l-smash which is libav/ffmpeg based)

[Cornucopia]

Just as with ASF, where you should not assume every codec inside is wmv and wma, so too mp4 can make use of a variety of codecs (both within the standard mpeg family and now without), and can be created from a variety of sources - not all of which are compatible with each other. If fact, this flexibility is the reason most apps/devices are grouped by which LEVEL & PROFILE they support to further define their true capabilities beyond codec and certainly beyond just container.

Again, you should never just look at the container designation. Barring the aforementioned complications, it could also just be mistyped. Another reason why parsers like MediaInfo are invaluable. I've been relying on them for over a decade.

Why those? No clue.

Scott