整理一些显示系统相关名词
Charles Chan @ 2017-07-12 #Graphic #Terminology @Linux
Contents:
显示系统相关名词
| Long | Long[CN] | Short | Description | Notes[CN] | Others |
|---|---|---|---|---|---|
| Generic Buffer Management | GBM | Generic Buffer Management (GBM) is an API which provides a mechanism for allocating buffers for graphics rendering tied to Mesa. GBM is intended to be used as a native platform for EGL on drm or openwfd. The handle it creates can be used to initialize EGL and to create render target buffers. | Refer | ||
| Graphics Execution Manager | GEM | Due to the increasing size of video memory and the growing complexity of graphics APIs such as OpenGL, the strategy of reinitializing the graphics card state at each context switch was too expensive, performance-wise. GEM provides an API with explicit memory management primitives. Through GEM, a user space program can create, handle and destroy memory objects living in the GPU’s video memory. These objects, called “GEM objects”, are persistent from the user space program’s perspective, and don’t need to be reloaded every time the program regains control of the GPU. | Refer | ||
| Direct Rendering Manager | DRM | a subsystem of the Linux kernel, interfaces with the GPUs of modern video cards. DRM exposes an API that user-space programs can use to send commands and data to the GPU, and to perform operations such as configuring the mode setting of the display. | Refer | ||
| Cathode Ray Tube Controller | CRTC | A CRTC, or cathode ray tube controller, generates the video timings and reads video data from RAM attached to the CRTC to output it via an external character generator ROM (for text modes) or directly to the video output shift register (for high resolution graphics modes). | Refer | ||
| Connector | - | A connector represents where the display controller sends the video signal from a scanout operation to be displayed. Usually, the KMS concept of a connector corresponds to a physical connector (VGA, DVI, FPD-Link, HDMI, DisplayPort, S-Video …) in the hardware where an output device (monitor, laptop panel, …) is permanently or can temporarily be attached. | Refer | ||
| Overlay | In computing, hardware overlay, a type of video overlay, provides a method of rendering an image to a display screen with a dedicated memory buffer inside computer video hardware.The overlay is a dedicated buffer into which one app can render (typically video), without incurring the significant performance cost of checking for clipping and overlapping rendering by other apps. The framebuffer has hardware support for importing and rendering the buffer contents without going through the GPU. | 看起来，Overlay更像是一个硬件算法的概念，或者说是经过一个算法才会呈现。而Framebuffer是硬件本身，是直接呈现的，没有计算过程。 | Refer | ||
| Planes | A plane is not a hardware block but a memory object containing a buffer from which a scanout engine (a CRTC) is fed. The plane that holds the framebuffer is called the primary plane, and each CRTC must have one associated, since it’s the source for the CRTC to determine the video mode —display resolution (width and height), pixel size, pixel format, refresh rate, etc. | Refer | |||
| Sprite | In computer graphics, a sprite is a two-dimensional bitmap that is integrated into a larger scene. Originally sprites referred to independent objects that are composited together, by hardware, with other elements such as a background. | “精灵”一词首次作为图形术语出现，是在德州仪器的9918（A）视频显示处理器上。使用“精灵”作为术语，是因为精灵并不是帧缓冲中位图数据的一部分，而是“悬浮”于帧缓冲中的数据之上，没有对其中的数据产生影响，就像幽灵和精灵一样。 | Refer 1 2 | ||
| page-flip | In the page-flip method, instead of copying the data, both buffers are capable of being displayed (both are in VRAM). At any one time, one buffer is actively being displayed by the monitor, while the other, background buffer is being drawn. When the background buffer is complete, the roles of the two are switched. The page-flip is typically accomplished by modifying the value of a pointer to the beginning of the display data in the video memory. | Refer | |||
| front buffer/back buffer | The page-flip is much faster than copying the data and can guarantee that tearing will not be seen as long as the pages are switched over during the monitor’s vertical blanking interval—the blank period when no video data is being drawn. The currently active and visible buffer is called the front buffer, while the background page is called the “back buffer”. | Refer | |||
| Framebuffer | Many systems attempt to emulate the function of a framebuffer device, often for reasons of compatibility. The Linux framebuffer device was developed to abstract the physical method for accessing the underlying framebuffer into a guaranteed memory map that is easy for programs to access. This increases portability, as programs are not required to deal with systems that have disjointed memory maps or require bank switching. | Framebuffer机制模仿显卡的功能，将显卡硬件结构抽象掉，可以通过 Framebuffer的读写直接对显存进行操作。用户可以将Framebuffer看成是显示内存的一个映像，将其映射到进程地址空间之后，就可以直接进行读写操作，而写操作可以立即反应在屏幕上。这种操作是抽象的，统一的。用户不必关心物理显存的位置、换页机制等等具体细节。这些都是由 Framebuffer设备驱动来完成的。 | Refer 1 2 | ||
| Mesa | - | Mesa is an open-source implementation of the OpenGL, Vulkan and other specifications. | Refer | ||
| Kernel Mode Setting | KMS | In order to work properly, a video card or graphics adapter must set a mode —a combination of screen resolution, color depth and refresh rate— that is within the range of values supported by itself and the attached display screen. This operation is called mode-setting,and it usually requires raw access to the graphics hardware —i.e. the ability to write to certain registers of the video card.A mode-setting operation must be performed prior to start using the framebuffer, and also when the mode is required to change by an application or the user. | Refer | ||
| X Desktop Group | XDG | freedesktop.org was formerly known as the X Desktop Group, and the abbreviation “XDG” remains common in their work. | Refer | ||
| VESA Display Power Management Signaling | DPMS | VESA Display Power Management Signaling (or DPMS) is a standard from the VESA consortium for managing the power supply of video monitors for computers through the graphics card. Example usage includes shutting off the monitor after a period of idle time to save power. Some commercial displays also incorporate this technology. | Refer | ||
| Video Electronics Standards Association | VESA | Is a technical standards organization for computer display standards. | Refer | ||
| Horizontal blanking interval | 水平消隐间隔 | hblank | CRT screens display images by moving beams of electrons very quickly across the screen. Once the beam of the monitor has reached the edge of the screen, the beam is switched off, and the deflection circuit voltages (or currents) are returned to the values they had for the other edge of the screen; this would have the effect of retracing the screen in the opposite direction, so the beam is turned off during this time. This part of the line display process is the Horizontal Blank. | 显示器的描画装置（如阴极射线电子枪）从当前行的最右侧移动到下一行的最左侧花费的时间。 | Refer |
| vertical blanking interval | 垂直消隐间隔 | vblank | Is the time between the end of the final line of a frame or field and the beginning of the first line of the next frame. | 显示器的描画装置（如阴极射线电子枪）从右下角移动到左上角花费的时间。 | Refer |
| Horizontal synchronization | 水平同步 | hsync | The horizontal synchronization pulse (horizontal sync HSYNC), separates the scan lines. The horizontal sync signal is a single short pulse which indicates the start of every line. | 水平同步以行为单位。 | Refer |
| Vertical synchronization | 垂直同步 | vsync | Vertical synchronization (also called vertical sync or VSync) separates the video fields. In PAL and NTSC, the vertical sync pulse occurs within the vertical blanking interval. The vertical sync pulses are made by prolonging the length of HSYNC pulses through almost the entire length of the scan line. | 一个垂直同步周期包含了一个页面下的所有水平同步周期的总和。 | Refer |
| modeline | A modeline is a configuration line in xorg.conf or the XFree86 configuration file (XF86Config) that provides information to the display server about a connected computer monitor or television and how to drive it at a specified display resolution. | Refer |
Weston内部名词：
| Long | Long[CN] | Short | Description | Notes[CN] | Others |
|---|---|---|---|---|---|
| presentation feedback | The main feature of this interface is accurate resentation timing feedback to ensure smooth video playback while maintaining audio/video synchronization. Some features use the concept of a presentation clock, which is defined in presentation.clock_id event. | weston-1.9.0 \ protocol \ presentation_timing.xml | |||
| buffer object | bo | - | |||
| media stream counter | msc |