Audio works on DVD but not on its original MPEG-2 file

[tealgrey]

I have a question about audio in MPEG-2 files. I am sure this is normal behaviour for .mpg files but I would like to know if someone could describe why. In this case, out of interest, I am more curious about how the process works rather than creating a finished product.

I was in the process of learning how to create a DVD by taking a Quicktime movie I had mymovie.mov (was encoded in MPEG-4 exported from HyperEngine-AV) and converting it to MPEG-2 so that I could put it onto a DVD (the file becomes "mymovie.mpg"). I used a program called called "Burn" to do this conversion ("Burn" is found at http://burn-osx.sourceforge.net/).

Out of interest, I compared the two files on my computer before burning the final DVD:
mymovie.mov - the sound plays on my computer in QuickTime
mymovie.mpg - the sound doesn't play on my computer in QuickTime

Why is this?

The sound does work on the final DVD that is created from mymovie.mpg but I found it interesting that the actual mymovie.mpg file from which the DVD is made, doesn't play its sound on my computer - its sound works only after being authored onto the DVD.

I find this very interesting and would like to know why this is.

Using the movie inspector on QuickTime player I can see that mymovie.mpg is of the format: "MPEG2 MUXED". Is this significant?

Does the sound not play from mymovie.mpg on my computer because my computer needs some special software?

(I do already have the Quicktime Mpeg-2 playback software component).


Thank you for any explanation,

[Case]

QuickTime Player will not play the audio on MPEG files if the audio is in AC3 format. Use other players (VLC, MPlayer, MPEG Streamclip, etc) that do not have this limitation for playback.
The reason is probably a licensing issue with Dolby, but that is not official.

[tealgrey]

Thank you Case for clarifying this for me. You are right, I tried playing the MPEG-2 movie file (mymovie.mpg) in MPEG Streamclip and the sound works fine - it must just be an issue with a limitation in QuickTime Player as you suggested.

Thanks!