Information technology — Advanced image coding and evaluation — Part 2: Evaluation procedure for nearly lossless coding — Amendment 1: Evaluation procedure parameters for nearly lossless coding of high dynamic range media and image sequences
Technologies de l'information — Codage d'image avancé et évaluation — Partie 2: Mode opératoire d'évaluation pour codage presque sans perte — Amendement 1: Titre manque
Standards Content (Sample)
Information technology — Advanced
image coding and evaluation —
Evaluation procedure for nearly
AMENDMENT 1: Evaluation procedure
parameters for nearly lossless coding
of high dynamic range media and image
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Information technology — Advanced image coding and
Evaluation procedure for nearly lossless coding
AMENDMENT 1: Evaluation procedure parameters for nearly
lossless coding of high dynamic range media and image
Replace the text with:
This document normalizes evaluation and grading of a light coding system used for displays and display
systems but is independent of the display technology. The procedure measures whether an observer
can distinguish between an uncompressed reference and the reconstructed image or image sequence
to a pre-determined, statistically meaningful level.
The procedure compares individual images or image sequences with two possible forced choice
comparison test methods. The procedure relies on subjective evaluation methods designed to discern
coding imperfections on electronic colour displays of any technology or size.
Selections for testing a specific coding system has bearing on the results this procedure will yield, but
specific images or image sequences required for testing are not within scope, excluding an informative
annex describing self-test certification. Content categories may vary between end-usage products. For
example, content relevant to television manufacturers may or may not be relevant to computer display
manufacturers. Due to the nature of this procedure as a visual psychophysical test, the observer’s age is
considered a meaningful parameter of the results.
After 3.18 add 3.19 to 3.23:
high dynamic range
image or image sequence format range conveying a larger range of perceptible shadow and highlight
detail than in a standard dynamic range image or image sequence, with sufficient precision and
sufficient separation of diffuse white and specular highlights
plurality of images, either reference images or reconstructed test images, shown in progression
audial, visual or haptic signal indicating the correctness of an observer's response
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standard dynamic range
image or image sequence format conveying typical colour volume and rendering characteristics similar
to those specified in Recommendations ITU-R BT.709 or ITU-R BT.1886 or IEC 61966-2-1 (sRGB)
wide colour gamut
image or image sequence format rendered a colour range larger than standard dynamic range systems,
typically >75 % of the human visible spectrum
After AQL, add:
EOTF electro-optical transfer function
HDR high dynamic range
After RGB, add:
SDR standard dynamic range
WCG wide colour gamut
Add a new row at the end of Table 1:
Annex H forced choice paradigm with image side-by-side, cropped image
sequences (no interleaving) sequence comparison
Add a new paragraph at the end of 5.2:
Media mastered in high dynamic range should be processed following guidance in Annex G. If an HDR
display capable of rendering the media colour and brightness is available, experimenters should opt
for the procedure in an HDR display hardware processed workflow, see G.5. If an appropriate HDR
display is not available, this document provides an HDR software processed workflow that is display-
independent, see G.4.
Replace list item a) with:
a) Explain the use of the software to record image or image sequence assessments.
Replace list item e) with:
e) Explain if sensory feedback is provided (see 5.9), and which signal is correct or incorrect.
Replace list item a) with:
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a) Use the control images or sequences from the experiment as test images or image sequences.
Replace list item d) with:
d) Prompt the observer when a correct or incorrect response is entered. If incorrect, continue by
repeating the test image or image sequence until a correct response is entered.
Replace the subclause heading with:
5.4.1 Standard dynamic range lighting and display calibration
Replace list item c) with:
c) The surrounding walls and ceilings do not require a specific colour but shall not cause distracting
reflections that may affect the vision of the observer. An appropriate viewing booth is optionally
Replace Table 2 with:
Table 2 — Viewing distance versus display size and resolution
Table condition PPD
Viewing distance for SDR D equals the larger of the values
evaluation in the following formula or 12 cm
Viewing distance for SDR or D=
H ×tan( )
The experiment requires a consistent display orientation to be maintained and a mobile display may have a different
width and pixel resolution in landscape versus portrait orientation. PPD is calculated for each orientation. Detailed work
on computer displays and mobile devices tends to be closer than for general entertainment, e.g., television, and requires
evaluation with a more aggressive PPD than would be the case for Snellen acuity (30 cycles/degree or PPD = 60).
W is the screen width (cm) and H is the number of pixels across the display horizontally as viewed by the observer.
The minimum focusing distance for normal vision is predetermined as 12 cm by this document.
Snellen viewing distance may be used for SDR evaluation when the evaluator determines the display (television) is
large enough to cause observer discomfort when at a close viewing distance based on 30 PPD.
Add a new subclause after 5.4.3:
5.4.4 High dynamic range lighting and display calibration
Viewing conditions shall be consistent with ISO 3664 viewing conditions for images displayed on a high
brightness display, such as an HDR-capable television or a wide colour gamut test monitor. Exceptions
a) The luminance of the peak brightness displayed on the monitor shall be >300 cd/m .
b) Displays that do not contain calibration tables should be avoided. However, if used, this document
recommends televisions and monitors with colour, contrast and tint adjustment controls so that
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the light output can be characterized with a spectrometer and colour calibration completed using
any of a number of procedures noted by the monitor or TV maker. Deviations shall be noted in the
test report. The maximum luminance of the display used in the procedure shall be recorded by
using a 2 % white centre on a black field.
c) The surrounding walls and ceilings do not need to be a specific colour but shall not cause distracting
reflections that may affect the vision of the observer. An appropriate viewing booth is optionally
d) The display monitor shall render at least the number of bits per component present in the
Replace the first paragraph with:
An observer shall view image paired stimuli on the display for no more than 4 s. An observer shall view
image sequence paired stimuli for no more than 10 s.
Add the following paragraph at the end of 5.5:
The image viewing time may be extended to 10 s if the evaluator finds that the test display shows
temporal dithering effects, which tend to distract observers from clearly identifying dithering from
scintillations caused by image interleaving employed by the protocol in Annex B.
Add a new subclause after 5.8:
5.9 Sensory feedback
An experiment may provide an observer with sensory feedback after a response that indicates a correct
or incorrect response to the last trial. Feedback should be immediately recognizable but an otherwise
subtle cue through an audial, haptic or visual signal.
The evaluator should take care to not mix sensory feedback and a retry method (see 5.6) where a retry
can be initiated after sensory feedback. Use of both sensory feedback and retries is not allowed during
an experiment unless the feedback mechanism disables the retry mechanism.
Add a new row at the end of Table B.1:
0,125 24 3 4
Add two new subclauses after C.3:
C.4 Image sequence search and cropping procedure
C.4.1 Image sequence processing
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The process of determining the image sequences to be used in the experiment is performed by the
evaluator. The process involves the steps from Figure C.1, which uses an image an example. The
evaluator compresses the full sequence of images and inspects the results for artefacts.
The goal of this search is to identify regions within the test sequence that exhibit a bit-wise difference
between the reference (original) and test image sequences and are thus potentially visually degraded.
As part of the selection, the evaluator may review many sequences and select only a small fraction of
the examples of artefacts for inclusion in the experiment to determine the point at which an image
sequence may be visually impaired.
Once a sequence of artefacts is found, the evaluator crops a region centred about the artefact for
inclusion in the test set. Typically testing should exhibit artefacts for a high percentage of the sequence
duration, rather than only one frame, unless the objective of the testing is to identify whether an
artefact type is visible even if the artefact is present for a short duration. The cropping of the region of
interest will greatly reduce the time needed for observers to view the image sequence before making a
Guidance for content categories (see C.2), for session duration and for image selection (see C.3) is
applicable to image sequence testing.
C.4.2 Stimulus orientation
Stimuli may be presented to the observer in either landscape or portrait orientation. The evaluator
shall ensure the viewing position requirements for the observer are met, see subclause 5.4.3.
C.5 Image panning in a sequence
C.5.1 Image panning processing
C.5.1.1 Panning setup, direction and sequence length
An alternative image sequence preparation method analyses a single image by panning the image either
horizontally, vertically or diagonally within the test crop one pixel shift at a time. This method tests a
coding system for sensitivity to the start and end of coding blocks. Use the side-by-side image sequence
procedure in Annex H for the subjective task.
Figure C.3 — Example image panned horizontally
The evaluator prepares the image sequence as follows:
1) Select one image and a cropping area using the image processing techniques in subclause C.1.1 that
will compose the first frame of the image sequence. Figure C.3 (top image) shows the crop area
overlaying the coded and decoded image.
2) The crop area becomes a window at a fixed location on the display for viewing the reference and
test image sequences as the image pans through the window for several frames.
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3) The evaluator determines the direction, panning rate and number of panned frames.
i) Figure C.3 shows an example panning horizontally and to the right. Panning may travel
horizontally, vertically, or diagonally. The direction does not need to be the same for each trial
in an experiment.
ii) The evaluator selects a panning rate less than or equal to 30 Hz, otherwise motion silencing
may render impai