TEKTRONIX 4K/UHD Monitoring and Measurement Guidelines

TEKTRONIX 4K/UHD Monitoring and Measurement Guidelines

Background and 4K/UHD basic specifications

Tektronix's "4K/UHD Content Creation Guide" aims to address the technical pain points throughout the entire process of 4K/UHD content acquisition, storage, post production, and transmission. The core focus is on "how to ensure signal compliance and content quality through professional monitoring tools", and it is recommended to use Tektronix 8000 series waveform monitors/rasterizers as the core equipment.

4K/UHD core specifications

Category Details Key Parameters

Resolution movie level 4096 × 2160 pixels

Home grade (UHDTV1) 3840 × 2160 pixels

Enhanced technology with dynamic range support for HDR (high dynamic range) to enhance light and dark details

Color gamut supports ITU-R BT.2020 wide color gamut (wider coverage than BT.709)

Signal transmission high frame rate (50p/59.94p/60p) four link 3G-SDI

Low frame rate (23.98p-30p) HD-SDI

6 Core Challenges in 4K/UHD Content Creation

Challenge 1: Inter channel timing synchronization of Quad Link signals

The four link 4K/UHD signal consists of four independent SDI physical links. Due to differences in transmission paths (cable length, equipment delay), timing deviations are prone to occur, resulting in signal splicing errors.

Standard requirements:

According to SMPTE ST 425-5 standard, the inter channel delay at the output end of the device should be ≤ 400ns (approximately 29 clock cycles);

There is no unified standard for the receiving end, and users need to control the delay difference themselves. Tek 8000 series devices can tolerate a maximum of 1024 clock differences.

Monitoring and investigation:

Using Tek 8000 series patented Timing Display, compare the horizontal/vertical offset of Link B/C/D with Link A as a reference;

If a "Video Format Mismatch" error occurs, switch to "Single Link" mode and check if the formats (resolution, frame rate) of each link are consistent;

Check the specific delay value through "MEAS>Timing Display" and adjust the transmission path (such as replacing equal length cables).

Challenge 2: Video Payload Identifier (VPID) Monitoring

VPID (based on SMPTE ST 352 standard) is stored in the auxiliary data area for devices to quickly identify video formats (resolution, sampling rate, number of links, etc.), and is key to 4K/UHD format compatibility.

VPID structure and key fields:

VPID data consists of 5 core components: Ancillary Data Flag（ADF）、Data Identifier（DID=41h）、Secondary Data Identifier（SDID=01h）、 4 user data words (UDW1-4), checksum (CS), where:

Example of UDW Byte Core Function Key Values

UDW1 identification standard and link type 89h=SMPTE ST 425-5 (four link 3G-SDI), C0h=ST 2081-10 (single link 6G-SDI)

UDW2 image frame rate 2h=24/1.001fps, 5h=25fps, Ah=60/1.001fps

UDW3 sampling rate and color gamut 0h=4:2:2 (YCbCr), 2h=4:4:4 (RGB); 0h=BT.709、2h=BT.2020

UDW4 link number 01h=Link A, 41h=Link B, 81h=Link C, C1h=Link D

Monitoring tools and troubleshooting:

Video Session Display: Directly view the UDW1-4 bytes of each link's VPID. Normal four links require UDW1-3 to be consistent, and UDW4 should be 01h/41h/81h/C1h in the order of A → D;

ANC Data Inspector: locates the field/line position of VPID packets (such as Field1/Line9), verifies the checksum (Exp/ACT Chksum must be consistent);

Common problem: Link sequence error (such as Link B/C switching), physical connection needs to be adjusted to make UDW4 conform to the order.

Challenge 3: Choosing the right color gamut

4K/UHD supports ITU-R BT.709 (traditional HD color gamut) and ITU-R BT.2020 (wide color gamut). Choosing the wrong color gamut can result in color distortion, which needs to be matched with content requirements and display devices.

Two major color gamut core differences (CIE 1931 coordinates):

|Color gamut standard | Red (x, y) | Green (x, y) | Blue (x, y) | Applicable scenarios|

|ITU-R BT.709 | (0.640, 0.330) | (0.300, 0.600) | (0.150, 0.060) | Traditional HD, 4K compatible HD content|

|ITU-R BT.2020 | (0.708, 0.292) | (0.170, 0.797) | (0.131, 0.046) | 4K wide color gamut content (such as HDR videos)|

Color gamut conversion and verification:

The difference between brightness (Y) and color difference (Pb/Pr) calculation: The Y formula for BT.2020 is Y=0.2627R '+0.6780G'+0.0593B ', and BT.709 is Y=0.2126R'+0.7152G '+0.0722B';

Verification method: Using 100% split field color bar signals (including BT.709 and BT.2020 dual color gamut), in RGB waveform display, the signal level should be stable at 0% (0mV) and 100% (700mV) under the correct color gamut, without significant fluctuations.

Challenge 4: Determine the aspect ratio of input 4K/UHD content

The aspect ratio of 4K/UHD content varies depending on the application scenario (movies, TV), and it is necessary to verify whether the image is scanned and cropped correctly to avoid stretching or cropping.

Common aspect ratios and corresponding resolutions:

|Aspect ratio | Application scenarios | Image size (pixels) | Effective pixels/line|

|16:9 (1.778:1) | UHDTV1 (Home) | 3840 × 2160 | 3840 pixels/2160 rows|