{"id":21,"date":"2019-05-14T14:13:28","date_gmt":"2019-05-14T14:13:28","guid":{"rendered":"http:\/\/blogs.igalia.com\/aboya\/?p=21"},"modified":"2019-05-14T14:33:40","modified_gmt":"2019-05-14T14:33:40","slug":"validateflow-a-new-tool-to-test-gstreamer-pipelines","status":"publish","type":"post","link":"https:\/\/blogs.igalia.com\/aboya\/2019\/05\/14\/validateflow-a-new-tool-to-test-gstreamer-pipelines\/","title":{"rendered":"validateflow: A new tool to test GStreamer pipelines"},"content":{"rendered":"

It has been a while since GstValidate<\/a> has been available. GstValidate has made it easier to write integration tests that check that playback and transcoding executing actions (like seeking, changing subtitle tracks, etc…) work as expected; testing at a high level rather than fine exact\/fine grained data flow.<\/p>\n

As GStreamer is applied to an ever wider variety of cases, testing often becomes cumbersome for those cases that resemble less typical playback. On one hand there is the C testing framework intended for unit tests, which is admittedly low level. Even when using something like GstHarness<\/a>, checking an element outputs the correct buffers and events requires a lot of manual coding. On the other hand gst-validate so far has focused mostly on assets that can be played with a typical playbin, requiring extra effort and coding for the less straightforward cases.<\/p>\n

This has historically left many specific test cases within that middle ground without an effective way to be tested. validateflow attempts to fill this gap by allowing gst-validate to test that custom pipelines acted in a certain way produce the expected result.<\/p>\n

validateflow itself is a GstValidate plugin that records buffers and events flowing through a given pad and records them in a log file. The first time a test is run, this log becomes the expectation log. Further executions of the test still create a new log file, but this time it’s compared against the expectation log. Any difference is reported as an error. The user can rebaseline the tests by removing the expectation log file and running it again. This is very similar to how many web browser tests work (e.g. Web Platform Tests).<\/p>\n

How to get it<\/h2>\n

validateflow has been landed recently on the development versions of GStreamer. Before 1.16 is released you’ll be able to use it by checking out the latest master branches of GStreamer subprojects, preferably with something like gst-build<\/a>.<\/p>\n

Make sure to update both gst-devtools<\/a>. Then update gst-integration-testsuites<\/a> by running the following command, that will update the repo and fetch media files. Otherwise you will get errors.<\/p>\n

gst-validate-launcher --sync -L\n<\/code><\/pre>\n
Writing tests<\/h2>\n
The usual way to use validateflow is through pipelines.json<\/code>, a file parsed by the validate<\/code> test suite (the one run by default by gst-validate-launcher<\/code>) where all the necessary elements of a validateflow tests can be placed together.<\/p>\n
For instance:<\/p>\n
\"qtdemux_change_edit_list\":\n{\n    \"pipeline\": \"appsrc ! qtdemux ! fakesink async=false\",\n    \"config\": [\n        \"%(validateflow)s, pad=fakesink0:sink, record-buffers=false\"\n    ],\n    \"scenarios\": [\n        {\n            \"name\": \"default\",\n            \"actions\": [\n                \"description, seek=false, handles-states=false\",\n                \"appsrc-push, target-element-name=appsrc0, file-name=\\\"%(medias)s\/fragments\/car-20120827-85.mp4\/init.mp4\\\"\",\n                \"appsrc-push, target-element-name=appsrc0, file-name=\\\"%(medias)s\/fragments\/car-20120827-85.mp4\/media1.mp4\\\"\",\n                \"checkpoint, text=\\\"A moov with a different edit list is now pushed\\\"\",\n                \"appsrc-push, target-element-name=appsrc0, file-name=\\\"%(medias)s\/fragments\/car-20120827-86.mp4\/init.mp4\\\"\",\n                \"appsrc-push, target-element-name=appsrc0, file-name=\\\"%(medias)s\/fragments\/car-20120827-86.mp4\/media2.mp4\\\"\",\n                \"stop\"\n            ]\n        }\n    ]\n},\n<\/code><\/pre>\n
These are:<\/p>\n