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, GstTagDemux 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 GstTagDemux

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.

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