http://cornsyrup.org/~jason/gst-fakefilter.tar.gz

I'd like to see this plugin or at least the functionality included in gstreamer.
I use it for specialized applications which can't be or don't need to be their
own plugin such as audio fingerprinting and file hashing. I think it would also
be useful for prototyping plugins or testing algorithms before taking the time
to develop a full plugin.

Very over simplified example of usage:

pipeline = gst_parse_launch("filesrc ! fakefilter name=hash_filter ! asfdemux
name=tag ! fakesink");

hash_filter = gst_bin_get_by_name(GST_BIN(pipeline->pipeline), "hash_filter");

g_signal_connect(hash_filter, "chain", G_CALLBACK(filter_chain_cb), pipeline);

void filter_chain_cb(GstElement* filter, GstPad *srcpad, GstPad *sinkpad,
GstData *data, State *state)
{
    GstBuffer *buf = GST_BUFFER(data);
    sha1_update(&state->sha1_ctx, GST_BUFFER_DATA(buf), GST_BUFFER_SIZE(buf));
}