Audio in mind as DPP introduces QC document3 April 2014
The Digital Production Partnership (DPP), the UK broadcast industry body set up to oversee technical specifications for the delivery of TV programmes, published its Guidelines for quality control (QC) at the beginning of this week.
The document comes six months ahead of the transition to full digital delivery by UK broadcasters on 1 October. It includes what is described as a minimum set of tests and tolerances, which have been taken from the ongoing work of the EBU’s Strategic Programme for QC, which is still working on definitions of “all possible QC criteria”, plus guidance for implementation.
The aim of both the DPP and EBU is for comprehensive, automated QC (AQC) checks, supported by manual appraisal, to be carried out at the post-production houses where programme material is prepared. Spot checks on audio and video will be carried out by broadcasters on the beginning, middle and end of programmes prior to broadcast, as well as checking accompanying metadata.
The QC Requirements fall into five groups: DPP AS-11 compliance checks, automated audio checks, automated video checks, eyeball [sic] audio checks and eyeball video checks. Tests will be either mandatory, which must be passed to meet basic delivery standards; technical warnings, which should be reviewed in an edit suite and fixed if possible; and editorial warnings, covering sequences where the quality is not fully to spec but which can be justified in the context of the programme.
Audio is included in the DPP AS-11 tests as well as its own categories, including audio bit depth, audio channel count, audio encoding format, audio sampling rate and audio track duration matches (all of which are mandatory). Sound AQC covers audio clipping and drop out (editorial warnings), integrated programme loudness to -23 LUFS, phase reversal and maximum true peak (all mandatory) and dial norm to loudness mismatch (technical warning).
Kevin Burrows (pictured), DPP technical standards lead and chief technical officer for broadcast and distribution at Channel 4, comments, “The DPP’s QC guidelines offer a standardised set of checks expected prior to the digital delivery of broadcast programmes to the UK broadcasters. They are designed to streamline the QC process and help minimise the issues that can arise in programme delivery.”
Among those from the post-production sector responding to the new Guidelines was Crispin Black, data manager at Evolutions: “This impacts in various forms and everyone needs to watch out for the tracks and channels confusion that is currently plaguing file writers. The DPP spec is for one channel per track. With regards to QC of multi-track files it means we will be relying very heavily on tools that will allow us to set different parameters for different groups of tracks. For many post houses now we will often deliver two or three versions for the final product, each having to conform to similar but sufficiently different dynamic requirements. Planning that ahead of our mixing sessions is crucial for making the delivery go smoothly.”