[Mp4-tech] mp4v content in 3gp files

[Magnus Hoem]

Hi Girish,
mp4 and 3gpp are basically the same format, but there are minor  
diifferences. In mp4 the iods-box is mandatory (if I remember  
correctly), and it is not in 3gp. It is however not surprising that  
QT can play both (they claim to support both, and can create both  
types correctly). Mp4 supports mpeg4 and H264 video along with AAC  
audio. 3gpp can also contain H263 video and AMR audio, (which is not  
supported in mp4).
About the mp4v-file. Since the release of the video-enabled iPod  
there is some confusion about this extension. It used to be a 14496-2  
(mpeg4) elementary stream, but now Apple uses it for a more or less  
regular mov/3gpp-file with mpeg4 or h264 content (along with AAC  
audio) to be played on the iPod. Which one are you refering to? I  
think QT will have a problem playing the elementary stream, but if  
you insert it correctly into a mov, 3gp or mp4 container it should  
not be a problem at all. The iPod file should of course not cause a  
problem in QT.
Best regards,
Magnus
On 28 nov 2005, at 15.21, Girish Shenoy wrote:
> Hi All,
>
> First, I note that Quicktime (and also RealPlayer) plays .mp4 files  
> (i played some mp4 files successfully).
> Also both these are able to play .3gp files with non-mp4 content (I  
> played some files successfully here too).
> In fact the 3gp file format uses the format defined my mp4 to store  
> the mpeg-4 content.
>
> I noticed that I am not able to play 3gp files with mp4v content  
> using either of the players. Quicktime gives me an error -2010  
> "movie contains some invalid data" (quicktime player 7.0.3).
>
> Certain other open source (linux based) players are however able to  
> play the same files. Theoretically any player able to play 3gp file  
> and mp4 files should be able to play mp4v content from a 3gp  
> file.Since both 3gp and mp4 files are essentially the same base  
> format, I examined the mp4 file that was played successfully. The  
> only difference I found was that this mp4 file had an additional  
> "iods" box/atom.
>
> But the "iods" box/atom is not a mandatory box and in fact the 3gpp  
> file format spec mentions that these mpeg-4 architectural elements  
> need not be present and shall be ignored.
>
> Am I wrong in saying that iods is not required, is this the problem?
> Has anyone else faced this problem? Anybody know any answers?
>
> I would be grateful to any information on the above.
>
> Thanks in advance,
> Girish
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Magnus Hoem
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