[gst-devel] Getting *fixed* caps information for streams in a file?
sastraxi at gmail.com
Tue Nov 18 20:30:57 CET 2008
I'm trying to get specific information on the media streams attached to a
file. To do this I'm using decodebin2 (I have tried decodebin, as well).
My problem is that it seems to be dependent on the file whether or not media
streams are fixated after coming in through the new-decoded-pad callback.
I have tried:
- adding an async block on the pads and querying data later;
- adding a notify::caps callback and querying for the caps later (in this
- just checking inside new-decoded-pad; and
- iterating over the pads after they have all been found.
I have also attempted to attach the pads to sinkpads and see what
negotiation happens, but that didn't work. I tried that using
gstreamer-java, so I'm not 100% sure, but I messed around with it long
enough that it makes me think it's not the right way to go about things.
Finally, I was directed to this on the IRC channel:
This iteration method works exactly as my code did before -- I have three
video files, one of which results in "x-video-raw/rgb; x-video-raw/yuv" and
a fixated audio (8000hz, 8-bit, 1 channel, PCM), one of which results in a
fixated video and a basically-generic audio caps (as in, 1 to some high
number hz, 1 or 2 channels, ...), and the third video results in both being
I was also directed to
However, either I have implemented the idea here and it did not work in the
way I expected, or I did not implement it correctly for lack of
documentation. I think I did implement it correctly using async blocker
callbacks on the srcpads, though. Feel free to correct me.
Basically, I'm looking to query *all* information about a file, kind of like
how you can right-click on a file in Gnome's Nautilus and get properties
like frame size, framerate, codec, ...
I need all the pertinent information for the uncompressed format of each
stream, and the length (though the length calculation is working just fine
right now), enough information to know exactly how much space each frame
will need, and how to access the information in these frames in my
Finally, I'm looking to do this decoding a minimal amount of the bitstreams
(as there will be thousands of files to load at the start). Can anyone help
out with some code that is doing what I want?
Thanks a ton!
P.S. Apologies if this gets posted twice; I have cancelled my original
unauthorized posting, but you never know...
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