Quality control: automated and manual QC

Quality control is the gate every streaming delivery must pass. Before a title goes live, the service or an approved vendor checks the picture, sound, timed text and metadata against the specification. Some problems are found by software in minutes; others need trained operators watching the whole programme on reference monitors. A failed QC report can mean redelivery, extra costs and a missed launch date. Many of the most common picture faults trace back to the shoot: dead pixels on a sensor, flickering lights, banding from weak capture, focus problems and unnoticed boom shadows. This lesson explains how QC works, which problems it looks for, how reports are written and what the cinematographer can do to prevent failures.

Who does QC and when

QC happens at several stages.

• On set and in dailies: the DIT and dailies lab check every clip for technical problems, such as dead pixels, flicker, focus and exposure issues, and report them quickly so they can be fixed or reshot.
• In finishing: the post facility runs internal QC on the master before delivery, using automated tools and manual review.
• At delivery: the service or its QC vendor checks the delivered package, often with both automated and full manual passes.
• After launch: viewer reports and the service's own monitoring can reveal problems that were missed.

The earlier a fault is found, the cheaper it is to fix. A dead pixel noticed in dailies costs minutes to address; the same fault found in final QC may need fixes across hundreds of shots.

Automated QC

Automated QC software decodes the files and checks them against rules. It is fast and consistent, and it catches problems people might miss.

• File and package checks: correct formats, frame rate, resolution, timecode, IMF structure, hashes and metadata.
• Signal checks: video levels outside legal or full range, out-of-gamut colours, peaks above the mastering display's limit and incorrect HDR metadata.
• Picture artefacts: black frames, frozen frames, digital dropouts, compression blockiness and some kinds of flicker.
• Audio checks: loudness, true peak, phase problems, silence, clipping and channel layout.
• Timed text checks: timing, overlaps, reading speed and formatting rules.

Automated tools can produce false positives, such as a creative black frame or an intentionally clipped highlight. Operators review flagged items and decide whether they are real faults.

Manual QC

Manual QC means a trained operator watches the full programme, often in real time, on a calibrated reference display with good audio monitoring. Some services require separate manual passes for HDR and SDR. Operators look for problems software finds hard to judge:

• Focus and softness that is not intentional.
• Boom microphones, crew, equipment or reflections in frame.
• Dead, stuck or hot pixels, sensor spots and dust.
• Banding, posterization and noise that looks wrong.
• Visual effects errors, such as missing objects, edges and tracking slips.
• Continuity and editorial errors, such as flash frames or wrong shots.
• Sync problems between picture and sound.
• Subtitle, caption and forced narrative errors.

Operators log each issue with a timecode, a description, a severity and sometimes a still frame.

Severity levels and reports

QC reports usually classify each issue by severity. Names vary, but a common pattern is:

A report typically lists the title, episode, version, file names, QC date, tool versions, operator, monitoring setup and each issue with timecode, description, severity and status. When the creative team believes a flagged item is intentional, such as grain, lens flare or a deliberately soft dream sequence, the post supervisor asks for it to be marked as creative intent. Some services ask productions to declare such choices in advance.

Common picture faults and their causes

Many picture QC failures have predictable causes.

Photosensitive content

Rapid flashing lights and certain patterns can trigger seizures in people with photosensitive epilepsy. Broadcasters in some countries must test content against guidelines such as ITU-R BT.1702, which limits flashes and regular patterns, commonly to no more than three harmful flashes in any one-second period. Many streaming services and QC vendors run automated photosensitivity tests and either flag sequences, ask for changes or add warnings to the title page. Sequences with strobe effects, lightning, gunfire muzzle flashes, club lighting or flashing police lights deserve attention in the grade and edit.

What the cinematographer can do

Most picture QC failures can be prevented on set and in the grade.

• Test cameras for dead pixels and run pixel calibration routines before and during the shoot.
• Test practical lights and LED fixtures for flicker at the planned frame rate and shutter.
• Watch HDR highlights, saturated lights and fine patterns on set and in dailies.
• Shoot clean plates and keep notes for paint-outs of rigs and reflections.
• Ask dailies and the DIT to report technical issues every day.
• Declare intentional choices, such as heavy grain or flares, early with the post supervisor.
• Review the QC report and approve fixes that affect the look.

Waivers and redelivery

Sometimes a flagged issue cannot be fixed, or fixing it would harm the creative intent. In that case the post supervisor may ask the service for a waiver, a documented acceptance of the issue. A good waiver request explains what the issue is, why it occurs, why it cannot be fixed or why fixing it would change the intended look, and includes stills or clips. Services grant waivers sparingly, and some issues, such as file structure errors or incorrect metadata, are never waived. When fixes are needed, the facility usually redelivers only the affected material, often as an IMF supplemental package, and the service re-checks those parts. Keeping a clear log of every issue, its fix and its approval protects the production if questions come up later.