Adding upstream version 0.3.65.upstream/0.3.65upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+/** \page page_tutorial5 Tutorial - Part 5: Capturing Video Frames
+
+\ref page_tutorial4 | \ref page_tutorial "Index" | \ref page_tutorial6
+
+In this tutorial we show how to use a stream to capture a
+stream of video frames.
+
+Even though we are now working with a different media type and
+we are capturing instead of playback, you will see that this
+example is very similar to \ref page_tutorial4.
+
+Let's take a look at the code before we break it down:
+
+\snippet tutorial5.c code
+
+Save as tutorial5.c and compile with:
+
+    gcc -Wall tutorial5.c -o tutorial5 -lm $(pkg-config --cflags --libs libpipewire-0.3)
+
+Most of the application is structured like \ref page_tutorial4.
+
+We create a stream object with different properties to make it a Camera
+Video Capture stream.
+
+\code{.c}
+	props = pw_properties_new(PW_KEY_MEDIA_TYPE, "Video",
+			PW_KEY_MEDIA_CATEGORY, "Capture",
+			PW_KEY_MEDIA_ROLE, "Camera",
+			NULL);
+	if (argc > 1)
+		pw_properties_set(props, PW_KEY_TARGET_OBJECT, argv[1]);
+
+	data.stream = pw_stream_new_simple(
+			pw_main_loop_get_loop(data.loop),
+			"video-capture",
+			props,
+			&stream_events,
+			&data);
+\endcode
+
+We also optionally allow the user to pass the name of the target node where the session
+manager is supposed to connect the node. The user may also give the value of the
+unique target node serial (`PW_KEY_OBJECT_SERIAL`) as the value.
+
+In addition to the `process` event, we are also going to listen to a new event,
+`param_changed`:
+
+\code{.c}
+static const struct pw_stream_events stream_events = {
+	PW_VERSION_STREAM_EVENTS,
+	.param_changed = on_param_changed,
+	.process = on_process,
+};
+\endcode
+
+Because we capture a stream of a wide range of different
+video formats and resolutions, we have to describe our accepted formats in
+a different way:
+
+\code{.c}
+	const struct spa_pod *params[1];
+	uint8_t buffer[1024];
+	struct spa_pod_builder b = SPA_POD_BUILDER_INIT(buffer, sizeof(buffer));
+
+	params[0] = spa_pod_builder_add_object(&b,
+		SPA_TYPE_OBJECT_Format, SPA_PARAM_EnumFormat,
+		SPA_FORMAT_mediaType,       SPA_POD_Id(SPA_MEDIA_TYPE_video),
+		SPA_FORMAT_mediaSubtype,    SPA_POD_Id(SPA_MEDIA_SUBTYPE_raw),
+		SPA_FORMAT_VIDEO_format,    SPA_POD_CHOICE_ENUM_Id(7,
+						SPA_VIDEO_FORMAT_RGB,
+						SPA_VIDEO_FORMAT_RGB,
+						SPA_VIDEO_FORMAT_RGBA,
+						SPA_VIDEO_FORMAT_RGBx,
+						SPA_VIDEO_FORMAT_BGRx,
+						SPA_VIDEO_FORMAT_YUY2,
+						SPA_VIDEO_FORMAT_I420),
+		SPA_FORMAT_VIDEO_size,      SPA_POD_CHOICE_RANGE_Rectangle(
+						&SPA_RECTANGLE(320, 240),
+						&SPA_RECTANGLE(1, 1),
+						&SPA_RECTANGLE(4096, 4096)),
+		SPA_FORMAT_VIDEO_framerate, SPA_POD_CHOICE_RANGE_Fraction(
+						&SPA_FRACTION(25, 1),
+						&SPA_FRACTION(0, 1),
+						&SPA_FRACTION(1000, 1)));
+\endcode
+
+This is using a `struct spa_pod_builder` to make a `struct spa_pod *` object
+in the buffer array on the stack. The parameter is of type `SPA_PARAM_EnumFormat`
+which means that it enumerates the possible formats for this stream.
+
+In this example we use the builder to create some `CHOICE` entries for
+the format properties.
+
+We have an enumeration of formats, we need to first give the amount of enumerations
+that follow, then the default (preferred) value, followed by alternatives in order
+of preference:
+
+\code{.c}
+	SPA_FORMAT_VIDEO_format,    SPA_POD_CHOICE_ENUM_Id(7,
+					SPA_VIDEO_FORMAT_RGB,	/* default */
+					SPA_VIDEO_FORMAT_RGB,	/* alternative 1 */
+					SPA_VIDEO_FORMAT_RGBA,	/* alternative 2 */
+					SPA_VIDEO_FORMAT_RGBx,	/* .. etc.. */
+					SPA_VIDEO_FORMAT_BGRx,
+					SPA_VIDEO_FORMAT_YUY2,
+					SPA_VIDEO_FORMAT_I420),
+\endcode
+
+We also have a `RANGE` of values for the size. We need to give a default (preferred)
+size and then a min and max value:
+
+\code{.c}
+	SPA_FORMAT_VIDEO_size,      SPA_POD_CHOICE_RANGE_Rectangle(
+					&SPA_RECTANGLE(320, 240),	/* default */
+					&SPA_RECTANGLE(1, 1),		/* min */
+					&SPA_RECTANGLE(4096, 4096)),	/* max */
+\endcode
+
+We have something similar for the framerate.
+
+Note that there are other video parameters that we don't specify here. This
+means that we don't have any restrictions for their values.
+
+See \ref page_spa_pod for more information about how to make these
+POD objects.
+
+Now we're ready to connect the stream and run the main loop:
+
+\code{.c}
+	pw_stream_connect(data.stream,
+			  PW_DIRECTION_INPUT,
+			  PW_ID_ANY,
+			  PW_STREAM_FLAG_AUTOCONNECT |
+			  PW_STREAM_FLAG_MAP_BUFFERS,
+			  params, 1);
+
+	pw_main_loop_run(data.loop);
+\endcode
+
+To connect we specify that we have a `PW_DIRECTION_INPUT` stream. The third
+argument is always `PW_ID_ANY`.
+
+We're setting the `PW_STREAM_FLAG_AUTOCONNECT` flag to make an automatic
+connection to a suitable camera and `PW_STREAM_FLAG_MAP_BUFFERS` to let the
+stream mmap the data for us.
+
+And last we pass the extra parameters for our stream. Here we only have the
+allowed formats (`SPA_PARAM_EnumFormat`).
+
+Running the mainloop will start the connection and negotiation process.
+First our `param_changed` event will be called with the format that was
+negotiated between our stream and the camera. This is always something that
+is compatible with what we enumerated in the EnumFormat param when we
+connected.
+
+Let's take a look at how we can parse the format in the `param_changed`
+event:
+
+\code{.c}
+static void on_param_changed(void *userdata, uint32_t id, const struct spa_pod *param)
+{
+	struct data *data = userdata;
+
+	if (param == NULL || id != SPA_PARAM_Format)
+		return;
+\endcode
+
+First check if there is a param. A NULL param means that it is cleared. The ID
+of the param tells you what param it is. We are only interested in Format
+param (`SPA_PARAM_Format`).
+
+We can parse the media type and subtype as below and ensure that it is
+of the right type. In our example this will always be true but when your
+EnumFormat contains different media types or subtypes, this is how you can
+parse them:
+
+\code{.c}
+	if (spa_format_parse(param,
+			&data->format.media_type,
+			&data->format.media_subtype) < 0)
+		return;
+
+	if (data->format.media_type != SPA_MEDIA_TYPE_video ||
+	    data->format.media_subtype != SPA_MEDIA_SUBTYPE_raw)
+		return;
+\endcode
+
+For the `video/raw` media type/subtype there is a utility function to
+parse out the values into a `struct spa_video_info`. This makes it easier
+to deal with.
+
+\code{.c}
+	if (spa_format_video_raw_parse(param, &data->format.info.raw) < 0)
+		return;
+
+	printf("got video format:\n");
+	printf("  format: %d (%s)\n", data->format.info.raw.format,
+			spa_debug_type_find_name(spa_type_video_format,
+				data->format.info.raw.format));
+	printf("  size: %dx%d\n", data->format.info.raw.size.width,
+			data->format.info.raw.size.height);
+	printf("  framerate: %d/%d\n", data->format.info.raw.framerate.num,
+			data->format.info.raw.framerate.denom);
+
+	/** prepare to render video of this size */
+}
+\endcode
+
+In this example we dump the video size and parameters but in a real playback
+or capture application you might want to set up the screen or encoder to
+deal with the format.
+
+After negotiation, the process function is called for each new frame. Check out
+\ref page_tutorial4 for another example.
+
+\snippet tutorial5.c on_process
+
+In a real playback application, one would do something with the data, like
+copy it to the screen or encode it into a file.
+
+\ref page_tutorial4 | \ref page_tutorial "Index" | \ref page_tutorial6
+
+*/