Understanding the example with appsrc

[Wudo Balmus]

Hello,
I'm trying to understand the example for appsrc element described in the
official tutorial:

https://gstreamer.freedesktop.org/documentation/application-development/advanced/pipeline-manipulation.html

We specify caps like that:

 g_object_set (G_OBJECT (appsrc), "caps",
        gst_caps_new_simple ("video/x-raw",
                     "format", G_TYPE_STRING, "RGB16",
                     "width", G_TYPE_INT, 384,
                     "height", G_TYPE_INT, 288,
                     "framerate", GST_TYPE_FRACTION, 0, 1,
                     NULL), NULL);

Then, when need-data function is called, there is created a GstBuffer of
size:

size = 385 * 288 * 2;

filled with some color and pushed to appsrc.

Two questions:

1. Why there is component 385, not 384 in the size of the buffer? In caps
there was specified that the width is 384, but in the size of the buffer
385 appeared.
2. Why the size is multiplied by 2? Cannot we just send 1 frame? I tried to
remove the *2 component, but then the background becomes a different colour
than expected.
I tried also to modify duration, to make it 1fps, but still doesn't work.

Best regards,
Wudo
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