What is the gstreamer caps syntax?

Question

What is the syntax for caps, specifying media capabilities, in gstreamer? Caps are strings that specify the type of media allowed and look like "audio/x-raw-int,..." but I haven't been able to find good documentation on exactly what is allowed in a caps string.

Answer 1

The syntax is:

<type>[,<property>=<value>]...

Note that the type is not a MIME type, however much it may look like one.

You can find out which caps properties elements support by using gst-inspect. It will proviide "pad templates" for the element's pads, which will specify the ranges of caps supported.

The GStreamer plugin writer's guide also contains a list of defined types which describes properties for common audio, video and image formats.

Answer 2

Here is the format as far as I understand it:

caps = <caps_name>, <field_name>=<field_value>[; <caps>]
<caps_name> = image/jpeg etc
<field_name> = width etc
<field_value> = <fixed_field_value>|<ranged_field_value>|<multi_field_value>
<fixed_field_value> = 800 etc
<ranged_field_value> = [<lower_value>, <upper_value>]
<multi_field_value> = {<fixed_field_value>, <fixed_field_value>, <fixed_field_value>, ...}