Automated Quality Control


Thomas Dove TV-Bay Magazine
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by Thomas Dove
Issue 109 - January 2016
Automated quality control for file-based media has been available to broadcasters for over a decade. The Vidcheck team designed and produced the very first product in this area. We have been working on this type of software since 2003 and are probably the most experienced team anywhere in the world. Many existing users of other products have since adopted our solutions.

Like many other transitions, the one to tapeless workflows is taking longer than the hyperbole, largely due to the costs of transition and the confusion of the many different file types and formats that edit systems and broadcasters have been using. Consequently transfer to and from tape remained in wide use. A key date, at least in the UK, was the DPP requirement that all deliveries to major UK broadcasters from October 2014 2014 onward should be file-based and conform to the DPP specified file formats.

The ground covered by automated QC can be broadly divided into several areas. Firstly there are UK transmission requirements such as ensuring PSE and loudness compliance. Secondly there are typical UK broadcaster specifications including correct video levels and a DPP delivery certificate.

Finally there is usually a long list of delivery requirements specific to the company receiving the content. These could be file formats, video and audio codecs, video resolution, frame rates, bit rates, aspect ratio, time codes, file duration, video levels, sample rate, bit rate and so on ad nauseam.

Leaving QC until just before transmission is too late because no time is left to correct problems. The DPP Producers Guide to File Delivery recommends that QC starts during the production phase. It also advises that automatic QC be used to check and report key video and audio parameters at all stages though production, post-production and distribution before the files are even delivered to the broadcaster.

Automated error correction

The first QC software products only looked for problems. Second generation products like Vidchecker provide not only full QC testing but also perform automatic correction of key parameters. These include video black and chroma levels, colour gamut, audio levels and audio loudness. Also PSE (flashing) checks to ensure content conforms to OFCOM requirements. Vidchecker automatically re-encodes the corrected files, reducing the time and expense of putting material back through the edit process for manual correction and re-encode.

Our Vidfixer product provides additional auto correction of items such timecode, length of colour bars, and black sequences according to user specified requirements. If a corrected file is produced by Vidchecker/Vidfixer, it is a new file with a different filename (typically the original filename plus corr with the date and time, although other suffixes can be added).

PSE regulations are specified in ITU-R BT 1702 which limits changes in brightness, moving patterns, and red images that can be present within video transmitted on UK television. These requirements are mandatory: if your video goes out contravening ITU-R BT 1702, the penalties can be expensive.

Automated QC is far more accurate than the manual approach, not least because the software stays alert from start to finish of a file, without distraction and 'without blinking'. It doesn't need a constant supply of coffee, take breaks or spend time discussing last night's football with colleagues. The automated process also provides efficient and thorough logging of every incident that needed attention. For example, the PSE specification says that the limit is three flashes per second of ± 20 candelas/m luminance but only when the screen luminance of the darker image is below 160 candelas/m, covering at least 25% of the screen area (20% when the strict limit is applied). I am sure that all Kit-Plus readers can instantly spot when the luminance is below 160 candelas/m and has changed by ± 20 candelas/m within the given time. No? Nor me.

Cost-efficiency

A single Vidchecker licence can process and correct four files simultaneously. We also offer a special low cost version, Vidchecker-post, specially for post-production houses with fewer files to process each day. Vidchecker-post has the entire QC, PSE checking and auto correction features of Vidchecker but processes one file at a time instead of four. It comes with templates for testing to DPP, Netflix and Apple iTunes delivery requirements, making the job of conformance testing and reporting straightforward and affordable. By the way, if you enjoy reading specifications, the delivery requirements are perhaps the most difficult to deal with as they are often in long documents. The 'iTunes Video and Audio Asset Guide 5.0' is 37 pages long; the NetFlix equivalent is 31 pages long with numerous options. Many others are as large and complex.

Our Vidchecker, Vidchecker-post and Vidfixer are Windows software applications to provide automatic quality control and optional correction of file-based media. Vidchecker and Vidchecker-post have identical test and correction features except that Vidchecker will QC and correct four files concurrently using a single license. Vidchecker-post will QC and correct one file at a time (and is roughly half the price of Vidchecker). Vidfixer does everything Vidchecker does plus more corrections, and transcode.The Vidfixer design mindset is 'Where we find a problem, we will fix it if at all possible'.

* Thomas Dove developed the first product for auto QC of file-based content in 2003 and in 2010 founded VidCheck which supplies auto QC solutions for file-based digital content to many of the worlds top broadcast media companies


Tags: iss109 | vidcheck | vidchecker | vidfix | qc | pse | Thomas Dove
Contributing Author Thomas Dove

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