A method for preventing tearing effect

Abstract

A method for preventing tearing effect, which is applied to a display driver chip. The display driver chip includes a frame memory, a display channel, and a synchronization signal generator that provides synchronization signals to the frame memory and the display channel. The method for preventing tearing effect includes: when detecting the power-on timing, adding a WAIT state to the synchronization signals generated by the synchronization signal generator. The WAIT state starts when the VACTIVE state ends and terminates when receiving the VSYNC from an external application processor. The power-on timing is when receiving a sleep command from an external application processor. For display purposes, the display driver chip internally adjusts the power-on timing of the power state. This method can eliminate the tearing effect generated when using a display driver chip with a built-in frame memory in video mode.

Description

Technical Field

[0001] The present invention relates to the field of display driver chips, and specifically to a method for preventing tearing effect (TE). Background Art

[0002] In the conventional display systems in the past, display driver chips are divided into: display driver chips without built-in frame memory and operating in video mode, and display driver chips with built-in frame memory and operating in command mode.

[0003] However, in the face of the increasingly complex and diverse requirements for display conditions and functions in reality, even display driver chips operating in command mode may need to operate in video mode in a specific system, and in a system operating in video mode, there may also be a situation where the built-in frame memory of the display driver chip needs to be used for display.

[0004] For example, in a system operating in video mode, when the display driver chip needs to use an internal up-scaler, or although it is in video mode, in order to reduce the overall power consumption of the system, when the image does not change, the application processor (AP) sends the image at a low frame rate, and the display driver chip needs to first store it in the internal memory and then display it at a frame rate higher than that sent by the application processor.

[0005] In this way, in a system operating in video mode, when the display driver chip needs to use the built-in frame memory for display, since there is no TE pin required for synchronization between the application processor and the display driver chip, a tearing effect will occur.

[0006] In order to eliminate the tearing effect occurring in a system operating in video mode, it is necessary to implement a function in the display driver chip to synchronize with the image sent by the application processor.

[0007] In view of the above research, the present invention application is proposed. Summary of the Invention

[0008] The object of the present invention is to provide a method for preventing tearing effect. By adding a WAIT state, the time difference d between the synchronization signal from the application processor and the synchronization signal generated inside the display driver chip is always kept constant, thereby avoiding the occurrence of tearing effect.

[0009] The technical solution adopted by the present invention is as follows:

[0010] A method for preventing tearing effect, which is applied to a display driver chip. The display driver chip includes a frame memory, a display channel, and a synchronization signal generator that provides synchronization signals to the frame memory and the display channel. The method for preventing tearing effect includes: when detecting the power-on timing, adding a WAIT state to the synchronization signals generated by the synchronization signal generator. The WAIT state starts when the VACTIVE state ends and terminates when receiving the VSYNC (Vertical Synchronization) from an external application processor. The power-on timing is when receiving a sleep command from the external application processor, and the display driver chip adjusts the power state internally for display during the power-on timing.

[0011] As a solution, add the WAIT state only to the first frame after the power-on timing.

[0012] As another solution, add the WAIT state only within the frame during the power-on timing.

[0013] There is also a solution to add the WAIT state to each frame after the power-on timing.

[0014] Preferably, the method for preventing tearing effect further includes, during the WAIT state, sending image data for generating a black image to the display panel.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects:

[0016] It can eliminate the tearing effect generated when using a display driver chip with a built-in frame memory in video mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Shows the external interface and internal frame synchronization signals when using a display driver chip with a built-in frame memory in a system operating in video mode;

[0018] Figure 2 Shows the normal operation of the video mode interface and the internal synchronization signals of the display driver chip;

[0019] Figure 3 Shows the timing relationship between the frame synchronization signals generated in the display driver chip after sleep and the frame synchronization input through MIPI (Mobile Industry Processor Interface);

[0020] Figure 4 Shows the timing diagram included in the function proposed to prevent the tearing effect. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0022] Figure 1 It shows how frame synchronization is configured and operates when the display driver chip uses the built-in frame memory in a system operating in video mode. Generally, since the video mode operating system does not use the frame memory, the frame synchronization signal entering through the external interface is directly used.

[0023] However, due to certain special reasons, when the display driver chip must use the frame memory internally, the display driver chip needs to generate and use the frame synchronization signal internally for display operation. In the figure, 101 represents the video mode interface signal of MIPI, including PCLK, VSYNC (Vertical Synchronization), HSYNC (horizontal synchronization), DE (valid data strobe), and RGB_DATA. Among them, VSYNC, HSYNC, and DE are used as frame synchronization signals. 102 represents the frame synchronization signal generated internally by the display driver chip for display, including VSYNC, HSYNC, and DE.

[0024] Figure 2 It shows the operation timing of the conventional synchronization signal for transmitting display data.

[0025] 201 represents the timing from VSYNC to the transmission of the actual display image data, denoted by VBP (Vertical BackPorch).

[0026] 202 represents the ACTIVE interval for transmitting image data between each HYSNC, denoted by VACTIVE. The DE signal is in an active state during the timing of actual image data transmission.

[0027] 203 represents the timing between the transmission of image data and the next VSYNC, denoted by VFP (Vertical FrontPorch).

[0028] Figure 3 It shows the timing difference between the VSYNC signal 305 input through MIPI and the VSYNC signal 304 generated internally by the display driver chip after the application processor sends the sleep command SLPOUT 301 to the display driver chip.

[0029] Since there is no signal to synchronize the time between the VSYNC signal 305 input through MIPI and the VSYNC signal 304 generated internally by the display driver chip, the time difference 306 between the two signals is random, resulting in a tearing effect.

[0030] When the application processor sends a sleep command to the display driver chip, in order to perform display, the display driver chip makes various power - on sequence adjustments for power state internally. 302 represents the power - on sequence state at this time. After this state ends, the actual display runs in the subsequent SLEEP_OUT state 303.

[0031] Figure 4 It shows the method for preventing the tearing effect in this embodiment.

[0032] In the figure, 401 represents the period of the frame sent by the application processor through the MIPI video mode interface, and 402 represents the period of a frame inside the display driver chip.

[0033] Since multiple parameter values can be adjusted for the frame rate inside the display driver chip and can be set to be the same as the frame rate of the application processor, the same p is used to represent them. Figure 4 Assume that the frame rate inside the display driver chip is the same as the frame rate sent by the application processor. However, just making the frame rates match like this cannot prevent the tearing effect. Therefore, this embodiment proposes the following method for preventing the tearing effect.

[0034] As shown in 403, after the display driver chip enters the sleep state, after the VACTIVE of the first frame ends, it does not enter the VFP state but enters the WAIT state. This WAIT state keeps waiting until it receives the VSYNC coming in from MIPI, that is, it terminates when receiving the VSYNC from the external application processor. Therefore, the duration of the WAIT state is not fixed but variable.

[0035] As shown in 404, in the WAIT state, if it receives the VSYNC coming in from MIPI, it will enter the VFP state.

[0036] As shown in 405, in this way, the period of this frame is not p but p + WAIT, which is longer than other frames.

[0037] Using this method, the frame synchronization signal input through MIPI and the frame synchronization signal generated inside the display driver chip can maintain a certain time difference.

[0038] The application processor is the same as the display driver chip. Since it repeats the VBP - VACTIVE - VFP states and transmits data through MIPI, as shown in 406, in the MIPI interface, after the VBP state passes, it enters the VACTIVE state and inputs image data. At this time, the input data starts to be stored in the frame memory inside the display driver chip.

[0039] Since the display driver chip reads the data in the frame memory for display in the VACTIVE state of the internal synchronization signal, as shown in 407, the time difference d represents the difference between the time when the frame memory starts writing data and the time when the frame memory starts reading data.

[0040] Adjust the parameter value for adjusting the frame rate inside the display driver chip to determine the difference d between the MIPI frame synchronization and the internal frame synchronization value, and keep the d value of each frame unchanged all the time, then the tearing effect can be avoided.

[0041] Although the above-mentioned tearing effect can be prevented, the periods of other frames are all p, and the period of the frame with the added WAIT state is p + WAIT. Since the increased period may affect the operation of the panel, it is better to add a function to send the image data for generating a black image to the display panel in the WAIT state, so that the panel displays a black image to replace the image input by MIPI for this frame.

[0042] In the above embodiment, starting from the end of the power-on timing, and adding the WAIT state only to the first frame after the power-on timing is the best solution.

[0043] As a sub-optimal solution, adding the WAIT state to the frame during the power-on timing can also keep the d value of each frame unchanged all the time, thereby avoiding the occurrence of the tearing effect.

[0044] As an extended solution, the WAIT state can be added to each frame after the power-on timing. By adding the WAIT state to each frame, the d value of each frame can be kept unchanged all the time, thereby avoiding the occurrence of the tearing effect.

[0045] It should be understood that in the above embodiment, taking the MIPI interface as the video mode interface is only a specific example, and this method is equally applicable to the general RGB interface system with a non-MIPI interface.

[0046] The present invention has been described in detail through specific embodiments. These detailed descriptions are only limited to helping those skilled in the art understand the content of the present invention, and should not be construed as a limitation on the protection scope of the present invention. All kinds of modifications, equivalent transformations, etc. made by those skilled in the art under the concept of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preventing tearing effect, which is applied to a display driver chip. The display driver chip includes a frame memory, a display channel, and a synchronization signal generator that provides synchronization signals to the frame memory and the display channel. Characterized in that, The method for preventing tearing effect includes: when detecting the power-on timing, adding a WAIT state to the synchronization signal generated by the synchronization signal generator. The WAIT state starts when the VACTIVE state ends and terminates when receiving the VSYNC from an external application processor. The power-on timing is when receiving a sleep command from an external application processor, and the display driver chip adjusts the power state internally for display during the power-on timing.

2. The method for preventing tearing effect according to claim 1, Characterized in that, Adding the WAIT state only to the first frame after the power-on timing.

3. The method for preventing tearing effect according to claim 1, Characterized in that, Adding the WAIT state only to the frame during the power-on timing.

4. The method for preventing tearing effect according to claim 1, Characterized in that, Adding the WAIT state to each frame after the power-on timing.

5. The method for preventing tearing effect according to claim 1, Characterized in that, The method for preventing tearing effect further includes, during the WAIT state, sending image data for generating a black image to the display panel.

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