VESA 时序标准 CVT V1.2.pdf

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39899 Balentine Drive, Suite 125 Newark, CA 94560 Phone: 510 651 5122 Fax: 510 651 5127 VESA Coordinated Video Timings (CVT) Standard Version 1.2 February 8, 2013 Purpose The VESA Coordinated Video Timings (CVT) Standard is a method for generating a consistent and coordinated set of standard formats, display refresh rates and timing specifications for computer display products, both those employing CRT and those using other display technologies. The intention of this standard is to give source and display manufacturers a common set of tools to enable new timings to be developed in a consistent manner that ensures greater compatibility. Summary CVT defines rules and methods by which new and existing formats can be defined. Based primarily on the VESA GTF Standard, CVT defines restrictions to pixel clock modularity, refresh rate and aspect ratio. The standard also specifies a new equation-based method for developing Reduced Blanking timings designed for use with non-CRT displays that can accept Reduced Horizontal Blanking times. VESA Coordinated Video Timings Standard Version 1.2 ©Copyright 2003-2013 Video Electronics Standards Association Version 1.2 Page 1 of 26

Preface Intellectual Property Copyright © 2003-2013 Video Electronics Standards Association. All rights reserved. While every precaution has been taken in the preparation of this standard, the Video Electronics Standards Association and its contributors assume no responsibility for errors or omissions, and make no warranties, expressed or implied, of functionality or suitability for any purpose. Trademarks All trademarks used within this document are the property of their respective owners. EDID, E-EDID, DDC, and VESA are trademarks of the Video Electronics Standards Association. I2C is a trademark owned by Philips. Patents VESA draws attention to the fact that it is claimed that compliance with this standard may involve the use of a patent or other intellectual property right (collectively, “IPR”) concerning CVT. VESA takes no position concerning the evidence, validity, and scope of this IPR. Attention is drawn to the possibility that some of the elements of this VESA Standard may be the subject of IPR other than any identified above. VESA must not be held responsible for identifying any or all such IPR, and has made no inquiry into the possible existence of any such IPR. THIS STANDARD IS BEING OFFERED WITHOUT ANY WARRANTY WHATSOEVER, AND IN PARTICULAR, ANY WARRANTY OF NON-INFRINGEMENT IS EXPRESSLY DISCLAIMED. ANY IMPLEMENTATION OF THIS STANDARD MUST BE MADE ENTIRELY AT THE IMPLEMENTER’S OWN RISK, AND NEITHER VESA, NOR ANY OF ITS MEMBERS OR SUBMITTERS, MUST HAVE ANY LIABILITY WHATSOEVER TO ANY IMPLEMENTER OR THIRD PARTY FOR ANY DAMAGES OF ANY NATURE WHATSOEVER DIRECTLY OR INDIRECTLY ARISING FROM THE IMPLEMENTATION OF THIS STANDARD. VESA Coordinated Video Timings Standard Version 1.2 ©Copyright 2003-2013 Video Electronics Standards Association Version 1.2 Page 2 of 26

Support for this Standard Clarifications and application notes to support this standard may be written. To obtain the latest standard and any support documentation, contact VESA. If you have a product, which incorporates CVT, you should ask the company that manufactured your product for assistance. If you are a manufacturer, VESA can assist you with any clarification you may require. All comments or reported errors should be submitted in writing to VESA using one of the following methods. • Fax : • • mail: Technical Support Video Electronics Standards Association 39899 Balentine Drive, Suite 125 Newark, CA 94560 510 651 5127, direct this note to Technical Support at VESA e-mail: support@vesa.org VESA Coordinated Video Timings Standard Version 1.2 ©Copyright 2003-2013 Video Electronics Standards Association Version 1.2 Page 3 of 26

September 10, 2003 Revision History Version 1.1 Section 3.4.1, points 6 & 7 revised to correct mistake (minimum Vertical Sync and Vertical Back Porch time is 550us not 500us). Rounding errors in VESA Standard Names corrected in Table 3 and 7. Missing Constants and Variables added to Table 9 and 10. Version 1 Initial release of the standard Version 1.2, Added section defining the timing generation rules for reduced blanking v2 rules. Updated sections 3.3.1, 3.4.3 and 5.4 to clarify the refresh rate error calculation and timing generation for video optimized vs. non-video optimized refresh rate February 8, 2013 March 26, 2003 VESA Coordinated Video Timings Standard Version 1.2 ©Copyright 2003-2013 Video Electronics Standards Association Version 1.2 Page 4 of 26

Acknowledgements This document would not have been possible without the efforts of the VESA DisplayPort Task Group. In particular, the following individuals and their companies contributed significant time and knowledge to this version of the CVT Standard. Table 1-0: Contributors to Version 1.2 Name Syed Athar Hussain David Glen Quinn Carter Greg Stewart Colin Whitby-Strevens Jamie Johnston Mrinalini Attaluri Jean-Jacques Ostiguy David Stears Craig Wiley Mark Stockfisch Alan Kobayashi Prashant Shamarao Company AMD AMD AMD Analogix Semiconductor Apple Intel Intel Matrox Graphics, Inc. Nvidia Parade Technologies Quantum Data, Inc. STMicroelectronics Synaptics Contribution Document Editor Task Group Chair VESA Coordinated Video Timings Standard Version 1.2 ©Copyright 2003-2013 Video Electronics Standards Association Version 1.2 Page 5 of 26

3.3 3.4.1 3.4.2 3.4.3 Table of Contents Revision History ............................................................................................................................................4 1. Overview .................................................................................................................................................8 1.1 Summary .............................................................................................................................................8 1.2 Background .........................................................................................................................................8 1.3 Standard Objectives ............................................................................................................................8 1.4 Reference Documents .........................................................................................................................9 2. Format & Timing Selection ..................................................................................................................10 2.1 Format Selection ...............................................................................................................................10 3. Timing Generation ................................................................................................................................11 3.1 Aspect Ratio ......................................................................................................................................11 3.2 Pixel Clock Selection ........................................................................................................................11 3.2.1 Minimum Clock Rate for Transmission .....................................................................................11 The Standard Vertical Refresh Rate Set ............................................................................................11 3.3.1 Determination of Vertical Refresh Rate Error ...........................................................................12 3.4 Rules for Timing Generation ............................................................................................................12 Standard CRT-based Timing .....................................................................................................12 Reduced Blanking Timing Version 1 ..........................................................................................13 Reduced Blanking Timing Version 2 ..........................................................................................14 Locking to External Timing Sources ................................................................................................15 3.5 3.6 Sync Polarities ...................................................................................................................................15 4. VESA Standard Display Formats .........................................................................................................17 4.1 Overview ...........................................................................................................................................17 4.2 VESA Format Naming Convention ..................................................................................................17 4.3 VESA Standard 4:3 Formats .............................................................................................................18 4.4 VESA Standard 5:4 Formats .............................................................................................................18 4.5 VESA Standard 15:9 Formats ...........................................................................................................18 4.6 VESA Standard 16:9 Formats ................................................................................................................19 4.7 VESA Standard 16:10 Formats .........................................................................................................19 5. Computation of Timing Parameters ......................................................................................................20 5.1 Explanation of Terms ........................................................................................................................20 5.2 Computation of Common Parameters ...............................................................................................20 5.3 Computation of "CRT" Timing Parameters ......................................................................................21 5.4 Computation of Reduced Blanking Timing Parameters ...................................................................21 5.5 Definition of Constants & Variables .................................................................................................22 6 Appendix A: Contributors to Previous Versions ....................................................................................26 VESA Coordinated Video Timings Standard Version 1.2 ©Copyright 2003-2013 Video Electronics Standards Association Version 1.2 Page 6 of 26

Tables Table 3-1: Sync Polarities ............................................................................................................................15 Table 3-2: Vertical Sync Duration ...............................................................................................................16 Table 4-1: Examples of 4:3 Formats ............................................................................................................18 Table 4-2: Standard 5:4 Formats ..................................................................................................................18 Table 4-3: Standard 15:9 Formats ................................................................................................................18 Table4-4: Examples of 16:9 Formats ...........................................................................................................19 Table 4-5: Examples of 16:10 Formats ........................................................................................................19 Table 5-1: Expression Terms & Operator ....................................................................................................20 Table 5-2: Definition of Constants ...............................................................................................................22 Table 5-3: Definition of Variables ...............................................................................................................23 Table 5-4: Delta between Reduced Blank Timing and Reduced Blank Timing V2 ....................................24 VESA Coordinated Video Timings Standard Version 1.2 ©Copyright 2003-2013 Video Electronics Standards Association Version 1.2 Page 7 of 26

1. Overview 1.1 Summary This document details an equation-based method of creating timings. Rules for timing generation are also specified so as to control the number of possible formats in existence. Additionally, this document also specifies a way of creating Reduced Blanking timings for new display devices such as LCDs that don’t require as much Horizontal Blanking timing as traditional CRTs. 1.2 Background The computer industry has, primarily due to the high degree of flexibility provided by continuous frequency CRT displays, traditionally employed a very wide range of display formats and timings even within a given individual system. This permits the system to adapt the display “on the fly” to the requirements of various applications, and also permits the user to adapt the system to a wide range of display-device formats, sizes, and technologies. However, to date, the development of timing standards for these various combinations of formats and rates has not been done in any sort of coordinated manner – and so we have a number of various standard formats which do not interoperate well, and timings which cannot all be precisely produced by any given graphics system. VESA first attempted to address this problem through the release of the Generalized Timing Formula (GTF) Standard in 1996. GTF defined a process whereby a given display device and host system could algorithmically determine a timing which would permit both to work together, reducing the need for explicit timing specifications to cover all possible cases. The GTF method works well on paper since it relies on being able to create a pixel frequency of infinite resolution. This, however, is not practical for real world applications where clock generators have a finite resolution. It also does not cater for an increasing market segment, such as “video in a window”, which requires the video timing to be precisely locked to an external image source. Also, due to the increasing number of non-CRT, fixed-format display types in the market, there is a need for timing standards that specifically address the requirements of these technologies. CRT-compatible timings require higher pixel rates than would be required by these other display technologies due to large amount of blanking which is required for retrace. This, in most cases, represents wasted bandwidth and results in higher-than-needed clock rates. In addressing these needs, though, it is important to keep in mind the fact that the computer graphics systems, which must produce video outputs to these specifications, are not infinitely flexible. In general, they cannot produce any arbitrary number of pixels per line, synthesize any given pixel clock exactly, and so forth. In addition, the problem of scaling information between different formats and rates says that we should not simply generate timings and formats as independent entities. Some thought should be given to the interoperability and compatibility within the chosen set, as well as to the ability of the graphics hardware to produce the specified timing. This standard represents an attempt to address these needs in a single, coordinated effort by developing a set of rules for generating timing. The goal was to create a method by which display manufacturers and graphic hardware vendors can develop new products with enhanced compatibility and interoperability. 1.3 Standard Objectives Previously the generation of new timing and formats has been done by hand and lagged the industry’s needs. This has caused confusion as new display devices or formats are introduced into the market with several different timings. The purpose of CVT is to define a method of creating timings so that new timings can be created simply and easily. CVT provides a coordinated approach so that timing source generators and display VESA Coordinated Video Timings Standard Version 1.2 Version 1.2 ©Copyright 2003-2013 Video Electronics Standards Association Page 8 of 26

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