Streaming support for video and metadata in GStreamer
GstExtractor is a GStreamer plug-in that extracts data embedded at the end of a video frame and allows the user to do customized parsing to send the embedded data downstream as KLV, H264/5 SEI metadata, or expose the data as a readable GstExtractor parameter, thus allowing the controlling application to retrieve the values of interest.
GstExtractor takes care of separating the embedded data from the actual video frame and output them to different pads, so that downstream video-processing elements will not know about the incoming extra data region. This separation is performed in a way that the video frame isn't copied so processing time is mainly due to the customized data parsing.
You can learn more about it in the following link:
GstExtractor uses GstSEIMetadata underneath, so the product is actually a bundle containing both, GstExtractor and GstSEIMetadata plugins.