GstTag.TagDemux

Subclasses:

None

Methods

Inherited:

Gst.Element (82), Gst.Object (27), GObject.Object (37)

Structs:

Gst.ElementClass (10), GObject.ObjectClass (5)

Virtual Methods

Inherited:

Gst.Element (16), Gst.Object (1), GObject.Object (7)

	do_identify_tag (buffer, start_tag, tag_size)
	do_merge_tags (start_tags, end_tags)
	do_parse_tag (buffer, start_tag, tag_size, tags)

Properties

Inherited:

Gst.Object (2)

Signals

Inherited:

Gst.Element (3), Gst.Object (1), GObject.Object (1)

Fields

Inherited:

Gst.Element (3), Gst.Object (1), GObject.Object (1)

Name	Type	Access	Description
element	Gst.Element	r	parent element
reserved	[object]	r

Class Details

class GstTag.TagDemux(**kwargs)

Bases:

Gst.Element

Abstract:

Yes

Structure:

GstTag.TagDemuxClass

Provides a base class for demuxing tags at the beginning or end of a stream and handles things like typefinding, querying, seeking, and different modes of operation (chain-based, pull_range-based, and providing downstream elements with random access if upstream supports that). The tag is stripped from the output, and all offsets are adjusted for the tag sizes, so that to the downstream element the stream will appear as if there was no tag at all. Also, once the tag has been parsed, GstTag.TagDemux will try to determine the media type of the resulting stream and add a source pad with the appropriate caps in order to facilitate auto-plugging.

Deriving from GstTag.TagDemux

Subclasses have to do four things:

• In their base init function, they must add a pad template for the sink pad to the element class, describing the media type they can parse in the caps of the pad template.

• In their class init function, they must override GST_TAG_DEMUX_CLASS(demux_klass)->identify_tag with their own identify function.

• In their class init function, they must override GST_TAG_DEMUX_CLASS(demux_klass)->parse_tag with their own parse function.

• In their class init function, they must also set GST_TAG_DEMUX_CLASS(demux_klass)->min_start_size and/or GST_TAG_DEMUX_CLASS(demux_klass)->min_end_size to the minimum size required for the identify function to decide whether the stream has a supported tag or not. A class parsing ID3v1 tags, for example, would set min_end_size to 128 bytes.

do_identify_tag(buffer, start_tag, tag_size) virtual

Parameters:

• buffer (Gst.Buffer) –

• start_tag (bool) –

• tag_size (int) –

Return type:

bool

identify tag and determine the size required to parse the tag. Buffer may be larger than the specified minimum size. Subclassed MUST override this vfunc in their class_init function.

do_merge_tags(start_tags, end_tags) virtual

Parameters:

• start_tags (Gst.TagList) –

• end_tags (Gst.TagList) –

Return type:

Gst.TagList

merge start and end tags. Subclasses may want to override this vfunc to allow prioritising of start or end tag according to user preference. Note that both start_tags and end_tags may be None. By default start tags are preferred over end tags.

do_parse_tag(buffer, start_tag, tag_size, tags) virtual

Parameters:

• buffer (Gst.Buffer) –

• start_tag (bool) –

• tag_size (int) –

• tags (Gst.TagList) –

Return type:

GstTag.TagDemuxResult

parse the tag. Buffer will be exactly of the size determined by the identify_tag vfunc before. The parse_tag vfunc may change the size stored in *tag_size and return GstTag.TagDemuxResult.AGAIN to request a larger or smaller buffer. It is also permitted to adjust the tag_size to a smaller value and then return GstTag.TagDemuxResult.OK in one go. Subclassed MUST override the parse_tag vfunc in their class_init function.