Gst.Check.Harness – gstreamer-check-1.0 Reference Manual

Harness

Object Hierarchy:

Object hierarchy for Harness

Description:

[ CCode ( cname = "GstHarness" , has_type_id = false ) ]
[ GIR ( name = "Harness" ) ]
[ Version ( since = "1.6" ) ]
public struct Harness

Harness is meant to make writing unit test for GStreamer much easier.

It can be thought of as a way of treating a Element as a black box, deterministically feeding it data, and controlling what data it outputs.

The basic structure of Harness is two "floating" Pad s that connect to the harnessed Element src and sink Pads like so:

          __________________________
 _____   |  _____            _____  |   _____
|     |  | |     |          |     | |  |     |
| src |--+-| sink|  Element | src |-+--| sink|
|_____|  | |_____|          |_____| |  |_____|
         |__________________________|

With this, you can now simulate any environment the Element might find itself in. By specifying the Caps of the harness Pads, using functions like set_src_caps or set_sink_caps_str, you can test how the Element interacts with different caps sets.

Your harnessed Element can of course also be a bin, and using gst_harness_new_parse supporting standard gst-launch syntax, you can easily test a whole pipeline instead of just one element.

You can then go on to push Buffers and Events on to the srcpad, using functions like push and push_event , and then pull them out to examine them with pull and pull_event.

A simple buffer-in buffer-out example

  #include <gst/gst.h>
  #include <gst/check/gstharness.h>
  GstHarness *h;
  GstBuffer *in_buf;
  GstBuffer *out_buf;

  // attach the harness to the src and sink pad of GstQueue
  h = gst_harness_new ("queue");

  // we must specify a caps before pushing buffers
  gst_harness_set_src_caps_str (h, "mycaps");

  // create a buffer of size 42
  in_buf = gst_harness_create_buffer (h, 42);

  // push the buffer into the queue
  gst_harness_push (h, in_buf);

  // pull the buffer from the queue
  out_buf = gst_harness_pull (h);

  // validate the buffer in is the same as buffer out
  fail_unless (in_buf == out_buf);

  // cleanup
  gst_buffer_unref (out_buf);
  gst_harness_teardown (h);

Another main feature of the Harness is its integration with the TestClock. Operating the TestClock can be very challenging, but Harness simplifies some of the most desired actions a lot, like wanting to manually advance the clock while at the same time releasing a ClockID that is waiting, with functions like crank_single_clock_wait.

Harness also supports sub-harnesses, as a way of generating and validating data. A sub-harness is another Harness that is managed by the "parent" harness, and can either be created by using the standard gst_harness_new type functions directly on the (GstHarness *)->src_harness, or using the much more convenient add_src or add_sink_parse. If you have a decoder-element you want to test, (like vp8dec) it can be very useful to add a src-harness with both a src-element (videotestsrc) and an encoder (vp8enc) to feed the decoder data with different configurations, by simply doing:

  GstHarness * h = gst_harness_new ("vp8dec");
  gst_harness_add_src_parse (h, "videotestsrc is-live=1 ! vp8enc", TRUE);

and then feeding it data with:

gst_harness_push_from_src (h);


Namespace: Gst.Check
Package: gstreamer-check-1.0

Content:

Static methods:

Methods:

Fields:


Generated by valadoc