Technical Requirements - Video
NOTE - This section is applicable to both file and tape deliveries. Specific requirements which are different for file and for tape are covered in separate sections 4 and 5.
1 High Definition Format
All material delivered for HD TV transmission must be:
1920 x 1080 pixels in an aspect ratio of 16:9
25 frames per second (50 fields) interlaced - now known as 1080i/25.
25 frames per second progressive, known as 1080psf/25 (“film mode”).
colour sub-sampled at a ratio of 4:2:2
The HD format is fully specified in ITU-R BT.709-5 Part 2.
Note: 1920 x 1080p/50 can not at the moment be accepted.
Material may be originated with either interlaced or progressive scan.
Interlaced and progressive scan material may be mixed within a programme if it is required for editorial reasons or the nature of the programme requires material from varied sources.
Electronically generated moving graphics and effects (such as rollers, DVE moves, wipes, fades and dissolves) must be generated and added as interlaced to prevent unacceptable judder.
1.3 Film motion or ‘film effect’
It is not acceptable to shoot in 1080i/25 and add a film motion effect in post-production. Most High Definition cameras can capture in either 1080i/25 or 1080p/25. Where film motion is a requirement, progressive capture is the only acceptable method.
1.4 Field dominance
Cuts in material must happen on frame boundaries (i.e. between field 2 and field 1). Motion on psf material must always occur between field 2 and field 1 (i.e. field 1 dominance).
Note - It is possible to shoot material at 1080p/50. If this is done, the correct 2-frame marker phasing must be maintained when down-converting to 1080i/25 or 1080psf/25 (SMPTE ST 2051).
2 Video Line-Up
Programme video levels must be accurately related to their associated line-up signals. Video line-up must be 100% colour bars (100/0/100/0) and filling the 16:9 raster. SMPTE pattern bars are not acceptable. For required durations, see Delivery Requirements below for Tape or File as appropriate.
2.3 Video Levels and Gamut (illegal signals)
High Definition digital signals will be assessed according to the recommendation ITU-R BT709-5 Part 2.
Video levels must be received within the specified limits so that the programme material can be used without adjustment. Any signal outside the specified limits is described as a gamut error.
2.3.1 Measuring signal levels
Digital video levels are usually measured with a device which displays a trace like a traditional waveform monitor. This gives readings in mV (emulating an analogue signal), or as a percentage of the allowable levels.
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The limits of signal levels are defined by reference to a nominal black level and a nominal white level. Black level comprises R, G and B all at zero (or 0% or 0mV) and white level is all three components at 100 % or 700mV.
In a picture signal, each component is allowed to range between 0 and 100% (or 0mV and 700mV). This equates to digital sample levels 16 and 235 (8-bit systems) or 64 and 940 (10 bit systems).
2.3.2 Tolerance of out of gamut signals
In practice it is difficult to avoid generating signals slightly outside this range, and it is considered reasonable to allow a small tolerance, which has been defined as follows under EBU Rec103:
RGB components must be between -5 % and 105% (-35 and 735mV) and
Luminance (Y) must be between -1% and 103% (-7mV and 721mV)
Slight transient overshoots and undershoots may be filtered out before measuring, and an error will only be registered where the out of gamut signals total at least 1% of picture area. Many monitoring devices are designed to detect errors to this specification.
HD images must fill the active picture area (1920 x 1080 pixels). No ‘blanking errors’ are permitted on new, up-converted, or archive material.
However a two-pixel tolerance will be permitted during CG or complex overlay sequences where key signals, graphic overlays or other effects do not fully cover the background image. Where animated key signals or overlays cause moving highlights at the edge of the active image it is preferable to blank these pixels completely. A note of the timecodes and reasons for these errors should accompany the delivered programme.
2.5 Aspect Ratio
All high definition programmes (except as below) must be delivered in 16:9 Widescreen. This means that the active picture must fill a 16:9 screen vertically and horizontally without geometric distortion.
2.5.1 ‘Cinemascope ratio’ letterbox
For delivery to dedicated movie channels or at the discretion of the broadcaster, programmes may be delivered with an active picture in the cinema ratios of 2.35:1 (21:9) or 1.85:1, centred vertically between black bars in a 16:9 frame, filling the width of the frame, and with no geometric distortion.
2.5.2 Floating images
Short sequences of images surrounded by black borders, (floating images), may be used for artistic effect. Note however, that widescreen consumer TV sets operating in Auto Zoom / Auto mode often interpret large black borders at the top and bottom of the screen as letterbox, so are likely to enlarge the picture. The resulting unpredictable zooming can be annoying for the viewer and undermine the artistic intent. If used, the black space around floating images must be consistent across sequences of images.
2.5.3 ‘Pillarboxed’ HD material
Some ‘pillar-boxed’ material is acceptable at the discretion of the broadcaster where it has been acquired on a medium that has the capability to be transferred to a legitimate HD resolution, for example, 35mm film shot using 4 perf at an aspect ratio narrower than 16:9. The pictures must be centrally framed in a 16:9 raster with no geometrical distortion.
2.6 Archive Material
Archive material must meet all the requirements in this document, including those for up-converted SD video where relevant.
2.6.1 General quality - archive
Archive material must be taken from the best available source, and any improvement or restoration work which could reasonably be expected must be done (for example grading, dropout repair or audio equalisation.)
2.6.2 Aspect ratio - archive
Archive material should be zoomed to fill the 16:9 raster where possible without compromising the image quality or composition, otherwise it may be presented in a pillar-box format, which:
may be of an intermediate ratio between 4:3 and 16:9, but must be of consistent width across sequences,
must be centrally framed in the 16:9 raster,
must show no geometrical distortion,
must have clean and sharp pillar-box edges (i.e. any video or film edge artefacts may need to be blanked.)
must be black outside the active picture, unless otherwise specified by the broadcaster.
Note however, that consumer TV sets operating in Auto Zoom / Auto mode may enlarge the picture to fill the screen horizontally. The resulting unpredictable zooming can be annoying for the viewer and undermine the artistic intent.
2.6.3 Safe areas - archive
Any captions or text already in the archive material should be kept within the caption safe area if possible, but if not, should be noted in the accompanying documents.
2.7 Use of Non-HD material
Some high definition programmes will contain some material from standard definition originals, and sources which are not considered to meet HD broadcast standards, such as domestic camcorders. This material is all called ‘non-HD’ in this document.
To maintain a high standard and meet audience expectations the amount of non-HD material is limited to 25% of the programme’s total duration. Non-HD material must not be used for large uninterrupted sections of the programme, unless agreed by the broadcaster. This includes archive material.
2.7.1 Non-HD material
Material acquired using the following methods or formats is considered to be below the high definition standard and will therefore be treated as non-HD:
HDV from all manufactures
Most cameras with image sensors under 1⁄2”
Frame based (intra-frame) recording formats below 100Mb/s
Inter-frame based recording formats below 50Mb/s
Material generated or processed on 720 line equipment
Film not meeting the requirement for HD in section 2.8 below
2.7.2 Up-converted SD video material
Particular care must be taken to deliver the best possible quality of up-converted material. In general standard definition pictures must look no worse than the original after being up converted, post processed and down converted. Only high quality up-conversion processes will achieve this.
Standard definition video contains a half-line at top and bottom on alternate fields. This must be removed on up-conversion to HD, or it will be visible flickering at top and bottom of the HD frame.
Any VITC or switching signals visible at the top of SD material must be removed.
Any line blanking from SD signals must not appear in the HD conversion.
For these reasons it is necessary that all SD material is zoomed in by a small amount on up-conversion.