How does buffering with HTTP and HTTPS work?

When playing a file fia HTTP or HTTPS, how far ahead the filter will buffer the stream, does the filter continue downloading the whole file at full speed until it is entirely downloaded or does it only read a short way ahead of the current playback location? How would the filter handle seeking?

The filter will try to download the largest available segment (i.e. progressive download) - like QuickTime Player would do. Seeking is available within the segment that has been downloaded to this moment. If seeking is outside of the already available segment, the playback will be stopped until the required segment is loaded. After the whole movie is loaded, your can make seeking like with normal file.