ISF Video Standards & Signal Processing 3 — Questions and Answers
Question 1: What is a key characteristic of the Hybrid Log-Gamma (HLG) HDR transfer function?
- It is backward-compatible with standard dynamic range displays without metadata (Correct answer)
- It requires static HDR metadata in the signal
- It uses an absolute luminance scale anchored to 10,000 nits peak
- It requires a dedicated decoding chip unavailable in standard TVs
Correct answer: It is backward-compatible with standard dynamic range displays without metadata
HLG was designed to be backward-compatible: SDR displays can render the signal acceptably without HDR metadata because the lower portion of the curve is a standard gamma function.
Question 2: In a progressive scan system, frames are sent at what rate compared to interlaced fields?
- Progressive frames are sent at half the field rate of the equivalent interlaced format (Correct answer)
- Progressive frames are sent at twice the field rate of the equivalent interlaced format
- Progressive and interlaced formats always share the same frame rate
- Progressive scan always operates at 60 frames per second regardless of format
Correct answer: Progressive frames are sent at half the field rate of the equivalent interlaced format
A 1080p/30 signal sends 30 complete frames per second, while 1080i/60 sends 60 fields (30 complete frames) per second—the same frame rate but delivered differently.
Question 3: What is quantization error in digital video?
- The difference between the true analog value and the nearest available digital code (Correct answer)
- Noise introduced by cable crosstalk during transmission
- Error caused by incorrect gamma encoding
- Distortion from overdriving the signal above white level
Correct answer: The difference between the true analog value and the nearest available digital code
Quantization error is the rounding difference between a continuous analog signal value and the discrete digital code assigned to represent it.
Question 4: Which of the following best describes 'legal' video levels in broadcast?
- Luma values constrained to 16–235 and chroma values to 16–240 in an 8-bit system (Correct answer)
- Luma values constrained to 0–255 with no chroma restrictions
- Any signal level that does not cause visible clipping on a consumer display
- Levels defined by HDMI licensing that prevent copy protection violations
Correct answer: Luma values constrained to 16–235 and chroma values to 16–240 in an 8-bit system
Broadcast-legal levels limit luma to codes 16–235 and chroma to 16–240 in 8-bit encoding, reserving headroom and footroom for sync and setup.
Question 5: What does the term 'metamerism' mean in the context of color science and display calibration?
- Two colors that appear identical under one light source but differ under another (Correct answer)
- The process of matching a display's white point to D65
- Color banding caused by insufficient bit depth
- The shift in perceived hue when luminance changes (Bezold-Brücke effect)
Correct answer: Two colors that appear identical under one light source but differ under another
Metamerism describes a pair of colors with different spectral compositions that appear identical under a specific illuminant but diverge under a different light source.
Question 6: In SMPTE ST 425, what does the quad-link 3G-SDI configuration allow?
- Transport of 4K/UHD video by combining four 3G-SDI signals (Correct answer)
- Redundant transmission of a single 1080p signal for reliability
- Embedding of Dolby Atmos audio within an SDI stream
- Conversion of SDI to IP using four parallel Ethernet ports
Correct answer: Transport of 4K/UHD video by combining four 3G-SDI signals
Quad-link 3G-SDI uses four 3 Gb/s SDI links simultaneously to transport 4K/UHD (3840×2160) content that exceeds the bandwidth of a single link.
Question 7: What is the relationship between the Nyquist frequency and sampling rate in digital video?
- The Nyquist frequency is half the sampling rate and sets the maximum frequency that can be accurately captured (Correct answer)
- The Nyquist frequency equals the sampling rate and determines pixel count
- The Nyquist frequency is twice the sampling rate, setting the minimum sampling needed
- The Nyquist frequency defines the bit depth required at a given sampling rate
Correct answer: The Nyquist frequency is half the sampling rate and sets the maximum frequency that can be accurately captured
The Nyquist theorem states that a signal must be sampled at least twice its highest frequency component, so the Nyquist limit is half the sampling rate.
ISF Video Standards & Signal Processing 3
What is a key characteristic of the Hybrid Log-Gamma (HLG) HDR transfer function?