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I am working with a video vendor who just ripped a dvd and sent me BOTH m4v files AND aac files (audio and video separately),. When I asked him why he did not just send 1 m4v file with the audio and video in ONE FILE, he wrote me back this (Which I need to confirm is true or false):

.M4V is a video format that doesnt directly support audio so the computer automatically rendered the audio files out as .AAC. What you say is an .MP4 format is really just the "file type" and not the extension itself.

Doesn't sound quite right, but I am not a video pro. But I do not want to have to splice all these files together again.

Please advise: Is his statement (above) correct?

Thanks, sleeper

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1 Answer 1

up vote 2 down vote accepted

I find the m4v extension a bit confusing.

For MPEG-2, the .m2v extension is associated with a raw video stream. Those files can have only video.

Now for MPEG-4, Apple uses the .m4v extension as a container format, and in fact if you rename an .m4v file to .mp4 it is likely to play on players that only read .mp4 files, since the two format are essentially equivalent.

I think you would need to check this .m4v file and make sure it is really the container format, and not an elementary video stream similar to what you find in .m2v files for MPEG-2.

If you feel comfortable inspecting files with a hex editor, just open this .m4v file, skip the first four bytes and check if the next four are the letters 'ftyp'. If they are, then you have an MP4 container file that should have no trouble holding audio along with the video. If, on the other side, you've got something else, then you may have an elementary stream, in which case you may want to recommend to your vendor to use a different extension for these files. Using .avc is probably more appropriate for an H.264 elementary stream.

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>> SO.. I think what your saying is the answer to my question is "MAYBE". And that .M4V is simply a container so it depends on some variable(s) within the container. I know nothing about working with a hex editor, plus the files came to me ALREADY split into audio and video files. So I guess I'm stuck with re-editing the files. –  sleeper Feb 2 '12 at 8:32
    
Are you on Windows, Mac or Linux? I can give you specific instructions for your OS to inspect the file if you want. –  Miguel Feb 2 '12 at 17:29
    
Yes. That would be great! Thank You so much. I'm on Windows 7 64bit (Home/Office) Windows. –  sleeper Feb 2 '12 at 20:34
    
Download the XVI32 hex editor from chmaas.handshake.de/delphi/freeware/xvi32/xvi32.htm#download. Then unzip to any folder (it does not come with an installer). Then double click XVI32.exe, select File|Open and then choose one of your .m4v files. Take a screenshot of the application window and paste it on your question. I'll take a look and tell you what it is. –  Miguel Feb 3 '12 at 5:44
    
I took the screenshot but unfortunately I do not yet have enough "Reputation Points" to post on the stack, so I posted it here on Google sites. (see attachment). Thanks again for your help. –  sleeper Feb 4 '12 at 23:38

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