[FFmpeg-devel] [PATCH] get the right value for the dac3 atom

vmrsss vmrsss
Fri Sep 5 01:42:44 CEST 2008


On 4 Sep 2008, at 19:43, Baptiste Coudurier wrote:
>> The are different ways of muxing ac-3 in mov, all valid. The dac3  
>> atom
>> inside mov has been used only by apple in QuickTime 7.5 when they
>> introduced an ac3 importer.
> It's standardized by ETSI now, so there is only one way to mux ac-3 in
> mp4. .mov is another story of course, but the official way will always
> be apple's one. I could not generate .mov containing ac-3 yet, samples
> welcome.

Well, my experience is that with current ffmpeg, x264 + ac3 works well  
in QT 7.5 if the extension is .mov and does not ("An invalid sample  
description was found in the movie") if the extension is mp4 (all the  
rest being equal). (for information, mplayer can't find the audio  
stream in any of the files, while ffplay plays them just fine.)  
Perhaps I can help with testing.

>> I think it's more important to test ac-3 in mp4. QuickTime can open  
>> it
>> only if the extension is m4v or m4a, and in this case it reads the
>> channels count and the sample rate from the dac3 atom.
> .m4v I could generate seems to use specs from ETSI.
>> Btw, on OS X and with an ac-3 component installed QuickTime is able  
>> to
>> play the files generated by ffmpeg without problems.
> Well, it must works "out of the box" without any other component I
> think, at least it did on my leopard with compressor 3, quicktime
> recognizes the track.

More information about the ffmpeg-devel mailing list