Element interface that allows setting of media metadata.
Elements that support changing a stream's metadata will implement this interface. Examples of such elements are 'vorbisenc', 'theoraenc'
and 'id3v2mux'.
If you just want to retrieve metadata in your application then all you need to do is watch for tag messages on your pipeline's bus. This
interface is only for setting metadata, not for extracting it. To set tags from the application, find tagsetter elements and set tags
using e.g. merge_tags or
add_tags. Also consider setting the TagMergeMode that is used for tag events that
arrive at the tagsetter element (default mode is to keep existing tags). The application should do that before the element goes to
PAUSED.
Elements implementing the TagSetter interface often have to merge any tags received from upstream and the
tags set by the application via the interface. This can be done like this:
GstTagMergeMode merge_mode;
const GstTagList *application_tags;
const GstTagList *event_tags;
GstTagSetter *tagsetter;
GstTagList *result;
tagsetter = GST_TAG_SETTER (element);
merge_mode = gst_tag_setter_get_tag_merge_mode (tagsetter);
application_tags = gst_tag_setter_get_tag_list (tagsetter);
event_tags = (const GstTagList *) element->event_tags;
GST_LOG_OBJECT (tagsetter, "merging tags, merge mode = %d", merge_mode);
GST_LOG_OBJECT (tagsetter, "event tags: %" GST_PTR_FORMAT, event_tags);
GST_LOG_OBJECT (tagsetter, "set tags: %" GST_PTR_FORMAT, application_tags);
result = gst_tag_list_merge (application_tags, event_tags, merge_mode);
GST_LOG_OBJECT (tagsetter, "final tags: %" GST_PTR_FORMAT, result);