[gst-devel] qtdemux source caps bad on .MP4 file with MP3 audio payload?

Tim Müller t.i.m at zen.co.uk
Thu Dec 6 20:23:18 CET 2007

On Thu, 2007-12-06 at 10:15 -0800, Edward Averill wrote:

> Ok, I'm seeing some really odd qtdemux behavior in my development
> here.

You're not saying which versions of things (core/base/good/bad) you're

> I have a .MP4 file that contains MP3 audio only.  It plays fine in
> VLC, which figures out it's MP3 audio.
> HOWEVER, when I run gst-launch using decodebin, it picks up qtdemux to
> to the parsing (which is the Right Thing), but the caps it sets for
> it's source pad say "mpegversion=(int)4" - which causes decodebin to
> load up an AAC decoder!  Things then go to heck in a handbasket,
> because the AAC decoder has no clue what it's being fed and errors
> out.
> This seems strange me.. I'd sure like to know why VLC understands that
> it's an MP3 audio payload but qtdemux seems to guess wrong.
> Anyone have any ideas what's going on here?  Could our MP3 decoder not
> be setting its typefind properly?
> All help appreciated!

The easiest thing would be to make a sample file available to us
somewhere and then file a bug against gst-plugins-good; then we can
check whether we can reproduce the problem with CVS of things or not
(see  http://gstreamer.freedesktop.org/bugs/ ).


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