TagSetter

class TagSetter(*args, **kwargs)

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);

Methods

class TagSetter

add_tag_value(mode: TagMergeMode, tag: str, value: Any) → None

Adds the given tag / GValue pair on the setter using the given merge mode.

Parameters:

• mode – the mode to use

• tag – tag to set

• value – GValue to set for the tag

get_tag_list() → TagList | None

Returns the current list of tags the setter uses. The list should not be modified or freed.

This function is not thread-safe.

get_tag_merge_mode() → TagMergeMode

Queries the mode by which tags inside the setter are overwritten by tags from events

merge_tags(list: TagList, mode: TagMergeMode) → None

Merges the given list into the setter’s list using the given mode.

Parameters:

• list – a tag list to merge from

• mode – the mode to merge with

reset_tags() → None

Reset the internal taglist. Elements should call this from within the state-change handler.

set_tag_merge_mode(mode: TagMergeMode) → None

Sets the given merge mode that is used for adding tags from events to tags specified by this interface. The default is GST_TAG_MERGE_KEEP, which keeps the tags set with this interface and discards tags from events.

Parameters:

mode – The mode with which tags are added