VIDEO SIGNAL TRANSMISSION

• US 20150288911A1
• Filed: 04/01/2015
• Published: 10/08/2015
• Est. Priority Date: 04/04/2014
• Status: Active Grant

• Current Assignee: Adder Technology Limited
• Original Assignee: Adder Technology Limited, Nexus Electronics Ltd. (Nexus 4 Holdings Ltd.)
• Inventors: DICKENS, Nigel, FIELD, Anthony
• Granted Patent: US 9,549,141 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G09G 2340/02 Handling of images in compressed format, e.g. JPEG, MPEG
• CPC Class Codes: G09G 2340/0407 Resolution change, inclusive of the use of different resolutions for different screen areas
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 2350/00 Solving problems of bandwidth in display systems
• CPC Class Codes: G09G 2370/12 Use of DVI or HDMI protocol in interfaces along the display data pipeline
• CPC Class Codes: G09G 5/00 Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators image data processing or generation, in general G06T
• CPC Class Codes: G09G 5/006 Details of the interface to the display terminal specific for a display terminal using a CRT G09G1/167; using a flat panel G09G3/2096; circuits for interfacing with colour displays G09G5/04
• CPC Class Codes: H04N 19/127 Prioritisation of hardware or computational resources
• CPC Class Codes: H04N 19/136 Incoming video signal characteristics or properties
• CPC Class Codes: H04N 19/587 involving temporal sub-sampling or interpolation, e.g. decimation or subsequent interpolation of pictures in a video sequence
• CPC Class Codes: H04N 19/59 involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution
• CPC Class Codes: H04N 5/38 Transmitter circuitry for the transmission of television signals according to analogue transmission standards H04N5/14 takes precedence
• CPC Class Codes: H04N 7/12 Systems in which the television signal is transmitted via one channel or a plurality of parallel channels, the bandwidth of each channel being less than the bandwidth of the television signal H04N7/24 takes precedence

Abstract

A digital video signal has a frame rate and a resolution within a range of resolutions. If the resolution of the received digital video signal is in a lower resolution range then it is not compressed or if in a higher resolution range the video colour data is compressed by a constant compression ratio. Frames of digital colour samples are transmitted and frames of digital colour samples are received at the same frame rate. The received compressed digital colour samples are expanded by a constant expansion ratio when transmitted in a compressed format and not expanded if transmitted in the uncompressed video format. A digital video signal is output with a resolution the same as the resolution of the original digital video signal.

Claims

1. A video transmission system, comprising:

a transmitter having;

an input arranged to receive a digital video signal having a frame rate and wherein the digital video signal has a resolution within a range of resolutions;

a detector configured to detect whether the resolution of the received digital video signal is in a lower resolution range or a higher resolution range;

a compressor configured to compress video colour data of the received digital video signal by a constant compression ratio when the detector detects that the resolution of the received digital video signal is in the higher resolution range and wherein no compression is applied to video colour data of the received digital video signal when the detector detects that the resolution of the received digital video signal is in the lower resolution range; and

an output arranged to transmit frames of digital colour samples at the same frame rate as the frame rate of the received digital video signal; and

a receiver having;

an input arranged to receive frames of digital colour samples from the transmitter;

a detector configured to detect whether the received digital colour samples were transmitted in a compressed format or an uncompressed format;

an expander configured to expand the received compressed digital colour samples by a constant expansion ratio when the detector detects that the received digital colour samples were transmitted in a compressed format, and wherein no expansion is applied to the received digital colour samples when the detector determines that the received digital colour samples were transmitted in the uncompressed video format; and

an output arranged to output a digital video signal with a resolution the same as the resolution of the digital video signal received at the input of the transmitter.

2. The video transmission system of claim 1, wherein the constant compression ratio is one half and the constant expansion ratio is two.

3. The video transmission system of claim 1, wherein the lower resolution range corresponds to single link DVI and the higher resolution range corresponds to dual link DVI.

4. The video transmission system of claim 1, wherein the lower resolution range corresponds to HDMI signal with a pixel clock frequency less than 165 MHz and the higher resolution range corresponds to HDMI signal with a pixel clock frequency greater than 165 MHz.

5. The video transmission system of claim 1, wherein the lower resolution range corresponds to a DisplayPort signal with an aggregate negotiated data rate less than 5.4 Gb/s and the higher resolution range corresponds to a DisplayPort signal with an aggregate negotiated data rate more than 5.4 Gb/s.

6. The video transmission system of claim 1, wherein the transmitter further includes a colour space converter configured to convert RGB video data into luminance video data and chrominance video data and wherein the receiver further includes a colour space converter configured to convert luminance video data and chrominance video data into RGB video data.

7. The video transmission system of claim 6, wherein the compressor of the transmitter comprises a chroma sub-sampler arranged to operate on the chrominance video data and the expander of the receiver comprises a chroma up-sampler arranged to operate on the chrominance video data.

8. The video transmission system of claim 7, wherein the chroma sub-sampler includes a first video line delay elements arranged to provide chrominance averaging over pixels of different video lines.

9. The video transmission system of claim 7 wherein the chroma sub-sampler includes a second video line delay element arranged to allow selection of a video line of an averaged first type of chrominance data and a video line of an averaged second type of chrominance data.

10. The video transmission system of claim 7, wherein the chroma up-sampler includes a first video line delay element arranged to allow selection of a first type of chrominance data and a second type of chrominance data for output on the same video line.

11. The video transmission system of claim 1, wherein the transmitter includes a switch operable by the detector either to supply the digital colour samples in the uncompressed format to the output of the transmitter or to supply the digital colour samples in the compressed format to the output of the transmitter and wherein the receiver includes a switch operable by the detector to supply the digital video signal including digital colour data obtained from the digital colour samples received in the uncompressed format to the output or to supply the digital video signal including digital colour data obtained from the digital colour samples transmitted in the compressed format.

12. The video transmission system of claim 1, and further comprising a cable connected between the transmitter and receiver and wherein the cable includes a plurality of twisted wire pairs.

13. The video transmission system of claim 12, wherein the cable includes only four twisted wire pairs and wherein the digital colour samples are can be transmitted over three of the twisted wire pairs and peripheral data can be transmitted over a fourth of the twisted wire pairs.

14. The video transmission system of claim 1, wherein the cable is at least 10 m long.

15. The video transmission system of claim 1 wherein the video transmission system comprises a KVM extender.

16. A video transmission method, comprising:

receiving a digital video signal having a frame rate at an input of a transmitter and wherein the digital video signal has a resolution within a range of resolutions;

detecting whether the resolution of the received digital video signal is in a lower resolution range or a higher resolution range;

compressing video colour data of the received digital video signal by a constant compression ratio when the resolution of the received digital video signal is detected to be in the higher resolution range and not compressing the video colour data of the received digital video signal when the resolution of the received digital video signal is detected to be in the lower resolution range;

transmitting frames of digital colour samples from an output of the transmitter to an input of a receiver;

receiving frames of digital colour samples at the input of the receiver at the same frame rate as the video signal were transmitted by the transmitter;

detecting whether the received digital colour samples were transmitted in a compressed format or an uncompressed format;

expanding the received compressed digital colour samples by a constant expansion ratio when it is detected that the received digital colour samples were transmitted in a compressed format and not expanding the received digital colour samples when it is detected that the received digital colour samples were transmitted in the uncompressed video format; and

outputting a digital video signal at an output of the receiver with a resolution the same as the resolution of the digital video signal received at the input of the transmitter.

17. The method of claim 16, wherein the constant compression ratio is one half and the constant expansion ratio is two.

18. The method of claim 16, wherein the lower resolution range corresponds to single link DVI and the higher resolution range corresponds to dual link DVI.

19. The method of claim 16, wherein the lower resolution range corresponds to a HDMI signal with a pixel clock frequency less than 165 MHz and the higher resolution range corresponds to a HDMI signal with a pixel clock frequency greater than 165 MHz.

20. The method of claim 16, wherein the lower resolution range corresponds to a DisplayPort signal with an aggregate negotiated data rate less than 5.4 Gb/s and the higher resolution range corresponds to a DisplayPort signal with an aggregate negotiated data rate more than 5.4 Gb/s.

21. The method of claim 16, further comprising the transmitter converting RGB video data into luminance and chrominance video data and wherein the receiver converting luminance and chrominance video data into RGB video data.

22. The method of claim 21, wherein compressing comprises sub-sampling the chrominance video data and expanding comprises up-sampling the chrominance video data.

23. The method of claim 22, wherein sub-sampling the chrominance video data includes introducing a first video line delay to average chrominance over pixels of different video lines.

24. The method of claim 22 wherein sub-sampling the chrominance video data includes introducing a second video line delay and selecting a video line of an averaged first type of chrominance data or a video line of an averaged second type of chrominance data.

25. The method of claim 22, wherein up-sampling the chrominance video data includes introducing a first video line delay and selecting a first type of chrominance data and a second type of chrominance data for output on the same video line.

26. The method of claim 16, further comprising:

operating a switch in the transmitter to supply digital colour samples in the uncompressed format or to supply digital colour samples in the compressed format to the output of the transmitter; and

operating a switch in the receiver to supply the digital video signal including digital colour data obtained from the digital colour samples in the uncompressed format or the digital video signal including digital colour data obtained from the digital colour samples in the compressed format to the output of the receiver.

27. The method of claim 16, wherein the digital colour samples are transmitted over a cable including a plurality of twisted wire pairs.

28. The method of claim 27, wherein the cable includes only four twisted wire pairs and wherein the digital colour samples are transmitted over three of the twisted wire pairs.

29. The method of claim 16, wherein the digital video signal is transmitted over a distance of at least 10 m.

30. The method of claim 16 and further comprising transmitting peripheral data from the receiver to the transmitter.