Overview
IEC 62375:2004 defines a standardized method for embedding video-related metadata into the vertical blanking interval (VBI) of the luminance (baseband analogue) signal for the 625-line / 50‑frame progressive scan video system. The standard covers the analogue interface used to transfer aspect-ratio codes, copy-control (CGMS‑A) and other companion data between digital and analogue video equipment.
Key topics and technical requirements
- Signal location and timing
- Data burst transmitted on line 43 of each frame; start at 5.5 μs ± 0.125 μs from horizontal sync.
- Electrical and timing parameters
- Clock: 10 MHz ± 1 kHz (sampling period T = 100 ns).
- Signal amplitude: 500 mV ± 25 mV (relative to 700 mV max video).
- Modulation and coding
- Uses bi‑phase-L (bi‑phase) coding; one data bit = 6 clock elements (T = 6·Ts).
- Preamble (run‑in + start code) precedes data.
- Data structure
- Total: 14 bits (13 data bits + 1 error/parity bit).
- Organized into 4 groups:
- Group 1 (4 bits): Aspect‑ratio label, letterbox/full format and parity.
- Group 2 (4 bits): Reserved.
- Group 3 (3 bits): Subtitles (in/out of active image area + reserved).
- Group 4 (3 bits): Surround sound / CGMS‑A / copy control and other flags.
- Aspect ratio encoding
- Encodes ranges (4:3, 14:9, 16:9, >16:9) and position (centre/top), with mapping to active line counts.
- Interoperability note
- Intended for systems complying with ITU‑R BT.1358 (625/50 progressive studio parameters).
Applications and who uses it
IEC 62375 is practical for:
- Broadcast and studio engineers embedding metadata into analogue progressive video signals.
- Video equipment manufacturers (analogue/digital converters, recorders, players) implementing CGMS‑A and aspect‑ratio signalling.
- Post‑production and transcoding facilities ensuring correct display (letterbox/full‑format) and subtitle placement.
- Test labs and compliance teams validating analogue interface behaviour and signal timing.
Embedding metadata in the VBI enables downstream devices to correctly display aspect ratio, honor copy‑protection flags, and place subtitles - improving compatibility between analogue and digital video systems.
Related standards and notes
- Normative reference: ITU‑R BT.1358 (studio parameters for 625 and 525 line progressive systems).
- The IEC foreword notes potential patent claims (Sony listed); manufacturers should verify licensing implications when implementing CGMS‑A.
Keywords: IEC 62375:2004, vertical blanking interval, 625/50 progressive, analogue interface, aspect ratio, CGMS‑A, copy control, VBI, bi‑phase coding.