When using such a launch line:
fakesrc ! "audio/x-opus, channel-mapping=(int)<0, 1>" ! fakesink
the caps string, with spaces escaped but no quotes gets passed to
gst_caps_from_string(), which then fails to parse the array because it
contains spaces.
When using an explicit capsfilter instead:
fakesrc ! capsfilter caps="audio/x-opus, channel-mapping=(int)<0, 1>" ! fakesink
the caps string, with spaces escaped and quotes gets passed through
gst_value_deserialize, which first calls gst_str_unwrap() on it and only
then gst_caps_from_string() on the result.
This fixes the inconsistency by using a custom version of str_unwrap()
in the parser, which doesn't expect a quoted string.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4181>
e4a26238a0