Re: GStreamermm: Gst::Taglist can not get Gst::TAG_DURATION?

[Ian Martin <martin_id vodafone co nz>]

On 08/12/11 08:53, Phong Cao wrote:

I went through the Gst::TagList reference and it is said that Gst::TagList::get_value(Gst::TAG_DURATION, Glib::ValueBase& value) required the variable "value" to be unsigned 64 bit integer (http://developer.gnome.org/gstreamermm/0.10/namespaceGst.html#ad14290dfbf163092d7a5c64b1cd76aee). So this is part of what I tried:

--
Phong V. Cao

phngcv gmail com

Hi Phong,
I don't know the gstreamer library at all, but I've had to play with GValues.
GValue is used as a type for any unknown data type in Gtk.  The tag list is an enum of labels which can be associated with any data type; they don't play nicely with the usual wrapping procedure.  For example, a  GST_TAG_ARTIST will be a string type; GST_TAG_TRACK_NUMBER is likely an int.  The GValue is a nice trick to work around that, but it appears to be a pain to wrap, and the C++ compiler doesn't like the absence of type safety.

If you're desperate, you could try modifying the gstreamermm source to fix it.  I've had to do this with another library, and managed to get it working with a template ( I am getting out of my depth here and can't guarantee this doesn't fall into the "ugly hack" namespace).
The taglist.h file in gstreamermm source declares 3 versions of get_value:
    bool get_value(Tag tag, Glib::ValueBase& dest) const;
    bool get_value(const Glib::ustring& tag, Glib::ValueBase& dest) const;
     bool get_value(const Glib::ustring& tag, guint index, Glib::ValueBase& dest) const;

To make them work, you could try something like this ( for the first type) in taglist.cc:

template <class ValueType> bool TagList::get_value(Tag tag, ValueType& v)
{
    bool valid_result = get_value(_tag_strings[tag], v);

    if(valid_result) return true;
    return false;
}

appropriately declared in the .h file.

Ian.