Analog and Digital Video Interfaces

Analog and Digital Video Interfaces

Analog and digital video signals may be connected by a variety of physical interfaces, largely depending on the signal type and application. All analog video signals are assumed to have a characteristic impedance of 75 Ohms.

Analog Interfaces

BNC

• Conforms to IEC 60169-8 Appendix A
• Adapters exist for connection from BNC to RCA and vice versa
• Equipment has female connectors (sockets)
• Cable is unbalanced coaxial
• Used in professional video products for CVBS, analog component video, and for serial digital component interfaces (SDI and HD-SDI)

RCA

• Also called Phono
• Adapters exist for connection from BNC to RCA and vice versa
• Equipment has female connectors (sockets)
• Cable is unbalanced coaxial
• Used in consumer video products for CVBS and component video

S-Video

• Uses a 4-pin miniature DIN connector
• Equipment has female connectors (sockets)
• Cable is two sets of unbalanced twisted pairs
• Typically used in consumer products
• The 4 pins are:
  1. Y ground
  2. C ground
  3. Ys (luminance + sync)
  4. C (chrominance)

VGA D-Sub

• Uses a 15-pin high-density D-Sub connector (3 rows in standard 9-pin D-Sub size)
• Equipment has female connectors (sockets)
• A common break-out cable converts to 5 x BNC male connectors for RGBHV signals
• Typically used by traditional computer graphics cards and where low form-factor component outputs are required
• The 15 pins are:
  1. R (Red video)
  2. G (Green video)
  3. B (Blue video)
  4. Sense 2
  5. Self test
  6. Red video ground
  7. Green video ground
  8. Blue video ground
  9. no pin
  10. Logic ground
  11. Sense 0
  12. Sense 1
  13. H (Horizontal sync)
  14. V (Vertical sync)
  15. Sense 3

SCART

• Uses a 21-pin Peritel SCART connector (also called Euro Connector) (BS EN 50049-1, IEC 933-1)
• Equipment has female connectors (sockets)
• Typically used on European products
• S-Video may replace composite and component signals on some pins (but must be supported by the product)
• Break-out cables can be used to connect to RCA and/or S-Video
• The pin connections defined by IEC 933-1 + amendment 1 are:
  1. Audio out R/mono
  2. Audio in R/mono
  3. Audio out L/mono
  4. Audio common return
  5. Blue video signal return
  6. Audio in L/mono
  7. Blue video signal (in/out)
  8. Function switching
  9. Green video signal return
  10. No connection
  11. Green video signal (in/out)
  12. No connection
  13. Red video signal return
  14. Blanking return
  15. Red video signal (in/out) or S-Video C (in/out)
  16. Blanking (in/out)
  17. Composite video out return
  18. Composite video in return
  19. Composite video out
  20. Composite video in or S-Video Y (in/out)
  21. Ground/shield
• The pin connections defined by IEC 933-2 are:
  1. Audio in L/mono
  2. Audio out L/mono
  3. Audio in common return
  4. Audio out common return
  5. Audio in R/mono
  6. Audio out R/mono
  7. Video in/sync in return
  8. Video out/sync out return
  9. Video in/sync in
  10. Video out/sync out
  11. Function switching
  12. S-Video Y control (in/out)
  13. Red video signal return
  14. S-Video Y/blanking common return
  15. Red video signal (in/out)
  16. Blanking (in/out)
  17. Green video signal return
  18. Blue video signal return
  19. Green video signal (in/out)
  20. Blue video signal (in/out)
  21. Ground/shield

Digital Interfaces

DVI-I

• Stands for Digital Visual Interface—Integrated (Digital/Analog)
• DVI-I accommodates digital and analog video signals
• Uses a special 24 + 5 pin D connector
• Adapters exist for connection from DVI-I to VGA and vice versa
• Equipment has female connectors (sockets)
• Analog video uses only the 5 separated pins (the center pin is a flat blade)
• Typically used by new-generation computer graphics cards
• The analog pins are:
  • 8. Vertical sync
  • 15. Sync ground
  • C1. Red
  • C2. Green
  • C3. Blue
  • C4. Horizontal sync
  • C5. Video ground

HDMI

• Is an abbreviation of High-Definition Multimedia Interface
• Is an all-digital interface capable of transmitting uncompressed streams of audiovisual content in high resolution
• Unlike DVI, the HDMI may also carry audio
• Utilizes TMDS signaling on 3 balanced signal pairs, plus one balanced clock pair
• The connector comes in three variants: Type A (normal 19-pin), type B (with additional link) and type C (for eg. cameras)
• HDMI is backward-compatible with a single-link DVI carrying digital video.
• You may connect an HDMI interface to a DVI-D or DVI-I interface through a suitable DVI-HDMI adaptor or cable.
• The features defined by the HDMI specification may or may not be utilized by product suppliers
• Refer to Digital Hardware for information about which devices are compliant with HDMI and DVI.
• The HDCP content protection scheme has been designed for HDMI
• The pin-out of the type A connector is:
  1. TMDS Data2 +
  2. TMDS Data2 shield
  3. TMDS Data2 -
  4. TMDS Data1 +
  5. TMDS Data1 shield
  6. TMDS Data1 -
  7. TMDS Data0 +
  8. TMDS Data0 shield
  9. TMDS Data0 -
  10. TMDS Clock +
  11. TMDS Clock shield
  12. TMDS Clock -
  13. CEC
  14. Reserved
  15. SCL
  16. SDA
  17. DDC/CEC ground
  18. +5 V power
  19. Hot plug detect

BT-656

This digital video signal format (525- and 625-lines interlaced BT-656) is acquired directly by NI VMS using the NI PXI-654x. To use this signal format, connect the clock from the source to the STROBE/PFI 5 pin on the NI PXI-654x Digital Data & Control connector.

BT-656 is always 4:2:2 coded. NI VMS supports from 1 bit to 16 bits of pixel depth, but in most cases the pixel depth is 8, 10, or 12 bits. BT-656 transfers all of the data bits for one color component in parallel at one clock pulse. For example, at one clock pulse, the data lines contain the red chrominance (Cr), then at the next they contain luminance (Y), blue chrominance (Cb) at the next, Y at the next, and so on.

Pixel clock is normally for 525-line video or for 625-line video, as illustrated in the following equations.

525-line video:

2 × 525 lines × 858 samples/line × (30/1.001 frames/second) = 27 MHz

625-line video:

2 × 625 lines × 864 samples/line × 25 frames/second = 27 MHz

Make the connections shown in the following table between the source and the NI PXI-654x, depending on pixel resolution, to acquire the BT-656 signal using NI VMS. Use the NI SCH68-H1X38 flying lead cable to make signal connections.