What is implicit for all QC Items
The following general rules should be kept in mind when looking at the Input and Output Parameters of the QC Items, unless specified differently for specific Parameters.
The system shall report deviation from the defined thresholds/tolerances
Note that the thresholds/tolerances may include user-defined expected, required or allowed values. These are defined as singular parameters, but it is implicit that lists of expected values may be used too. Example: an aspect ratio QC Item may have a user-defined expected value list of 4:3 and 14:9. The system shall report when the aspect ratio is 16:9.
The system shall report the relevant location(s) for each result.
For reporting of QC events, timecode, relative to the start timecode value of the container or bitstream is preferred for identifying the location(s) of an event. When the timecode track is discontinuous or not present, QC events could be reported relative to a start timecode of zero (0). Note that this may include timecode intervals. Example: an audio peak QC Item reports a crossing of -1dBTP for audio channel 1 from 10:01:01:22 to 10:02:03:13.
While systems should strive to report audio errors in relation to the relative video time (frames), it is understood that this may not always be possible, and in some cases, audio errors could be reported in HRS:MIN:SEC.MSC relative to a start time of zero. Framecount can be used as an additional time reference.
The system should report changes in measured values.
If the system will not report changes, this should be made clear to the user. Example: a system reports the aspect ratio is 4:3 from 10:00:02:00 to 10:02:02:00 and 16:9 from 10:02:02:00 to 10:03:00:00.
Service references
Multichannel audio services (programmes) that are embedded in a single track should reference the audio channels as mapped in the bitstream. For multichannel audio services (programmes) that are a collection of tracks (i.e., an EBU R123 map of AES channels or a Dolby E program in an AES stream), the audio channels should be referenced by the externally defined map for these tracks (i.e., EBU R 123 or the Dolby E program). For audio and/or video services in programme/transport streams, PIDs should be used for unique stream identification.
References
References in the v1.0 (and higher) versions of the QC Test Items refer to the latest version of a specification, unless they are explicitly dated. E.g. SMPTE ST 377-1:2009
Types of specs to reference
We are using a practical approach to referencing specs; which means we do not only reference formal standards, but also industry specs where relevant (e.g. Dolby-E specifics). This also is relevant in the video codecs domain (e.g. XDCAM, IMX, RDD-9, ...). The criterion is that the spec should be published.
Supported wrapper formats
Some QC Items are focussed on MXF, but can be relevant for other wrapper formats too. Due to resource constraints we do not include detail on the other wrappers (at least for now). Example: Quicktime.
Note that MXF-only tests are signalled using an ‘MXF’ logo in the QC Test card’s image and the 'MXF-only' tag.
Calculated values vs reported values
Any value that is calculated and not read out, should be clearly marked ‘calculated’. Example: duration calculated as (# of frames / frame-rate) should be reported as 'calculated'.
Checks on specific channels
We do not preclude systems to offer users the option to limit checks to certain channels. E.g. perform a silence check only on audio track 1 instead of on all channels. To limit the amount of generic text, we do not repeat this option for each QC Item, but regard it to be implicit, where relevant.
When tests cannot be done...
If information is not available, e.g. audio bit depth is not defined in the wrapper format used by a particular file, than a Test Item (and any related x-check) does not apply. For some QC Items we do not define wrapper tests, as we know the information typically is not available at the wrapper level.
Programme vs. non-programme content testing
System shall be able to apply test criteria between specified timecodes, e.g. from the start to the end of a programme, allowing line-up and non-relevant content (such as clean backgrounds for international markets) to be excluded.