QC Items apply to one or more layers:
Tests the structure/integrity of the file wrapper, or of the metadata within the wrapper.
Tests the structure/integrity of the encoded bitstream, or of the metadata within the bitstream.
A test applied to the decoded essence – the video frames or audio samples.
A verification that the values agree between multiple layers. For example, if a baseband test of video frame size has been completed, and the video frame size metadata in the format and wrapper have been examined, the X-check will verify that all values match.
Programme layout Items look for specific audio, video or audio-visual patterns or types that are located at specific time intervals. For example a programme may be required to contain 10 seconds of colour bars and tone followed by black and silence, then the programme content, followed by 5 seconds of black and silence.