[Matroska-users] playing decoded contents

Ivan Kowalenko ivan.kowalenko at gmail.com
Fri Jun 22 08:48:49 CEST 2007


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On Jun 14, 2007, at 14.12, Kunal Singh wrote:

> Hi All,
>
>    I am a MKV developer working with VC6/Windows-XP.
>    I am decoding a .MMV file and dumping the audio and video data  
> to binary files.

I'm assuming by "MMV" you meant to type "MKV"? I don't think MMV is  
actually a Matroska container.

>    I want to check the sanity of dumped data. Dumped Audio is "MP3"  
> format and I am able to play this file using Windows Media player.
>    Dumped Video is "V_MS/VFW/FOURCC" format. I have given the  
> dumped file a ".M4V" extension. But I am not able to play this file  
> using Windows-Media or VLC player.
>    Can some one help me?

You've dumped the data without any kind of header into an MPEG-ES (or  
Elemental Stream) which can't be identified by the players because  
(this is my guess, a copy of the error message out of VLC would help,  
don't bother with WMP's as it tends to be far too cryptic or  
nondescript) they can't figure out what this thing is. An MPEG-ES has  
no header, no descriptor, nothing like that. Therefore, programs that  
don't use the file's extension to determine it's type and contents,  
but instead rely on the header (like VLC) get seriously confused.

Furthermore, use of the M4V container is generally discouraged since  
it's more commonly associated with Apple's DRM-armored videos, as  
opposed to the old style M2V and M2A extensions which denoted MPEG-2  
video and audio streams (respectively). It's possible that this is  
also confusing your programs, and programs that rely on file  
extensions to determine file content (like Windows Media Player) will  
simply esplode.

There's a chance that QuickTime might play it, but it's unlikely. If  
you force the use of the proper codec. This also brings up an issue:  
VC6 isn't a part of the MPEG-4 spec, so it shouldn't belong in any  
MP4, M4V, M4A, M4B or M4P files. Improper use of an extension would  
also cause trouble in some media players (like WMP).

The reason your MP3 file worked is probably a combination of all  
three of the above reasons, and possibly because MP3 files themselves  
are really quite simple.
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