A technical method for measuring the relative delay between DLP projector image and sound and its application

Abstract

The present invention discloses a technical method for measuring the relative delay between the picture and sound of a DLP projector. The basic idea of ​​the invention is to reflect the audio and picture signals simultaneously and in real time on the waveform of an oscilloscope, and to accurately measure the relative delay of the audio and picture by measuring the time difference between the respective channels of the audio and picture through the oscilloscope. The invention focuses on solving the problem of how to convert the video signal into a signal waveform that can be intuitively reflected in the oscilloscope. By measuring the electrical signal of the video signal processing process in the projector, it is obtained that there is a respective delay between each link, and the time point when the representative picture is actually displayed on the screen or projected can be obtained. Based on the above ideas, a projector of a DLP projection technology platform, utilizing the characteristics of DLP technology, can establish a connection between the content of a specific picture and the driving current of the optical machine LED; an application of the technology for measuring the relative delay between the picture and sound of a DLP projector is mainly used for measuring the relative delay of audio and picture, and can set the delayed output time of the picture accordingly.

Description

Technical Field

[0001] The present invention relates to the fields of DLP display technology projection and Bluetooth audio, and more specifically, to a method for measuring audio and video synchronization of this type of projector. Background Art

[0002] The widespread use of Bluetooth headsets, speakers, and other products has freed users from the constraints of wires. However, because the Bluetooth audio transmission process involves multiple steps and processes, including audio encoding, wireless transmission, wireless reception, audio decoding, and DAC, Bluetooth audio latency is significantly higher than that of wired headsets and speakers. The SBC codec, currently mandatory for the Bluetooth A2DP protocol, introduces a latency of approximately 100 to 300ms. Therefore, accurately measuring the relative delay between sound and video is crucial for improving this problem. Furthermore, by measuring the relative delay between audio and video, it is possible to set a corresponding delay in video output, ensuring synchronization between audio and video.

[0003] The current conventional method for evaluating the relative delay between sound and picture is as follows:

[0004] By playing a test video, the principle of the same type of video is similar. The yellow line of the original video moves from left to right, and when it overlaps with the white bar in the middle, a "beep" sound is emitted at the same time. When using a playback device for actual playback, since the sound and picture may not be synchronized, the observer may hear a "beep" sound when the yellow bar is in another position. Therefore, based on the relative position of the yellow bar, the delay time of the sound relative to the picture (for example, Figure 2 If a "beep" sound is heard between the 3rd and 4th blue bars on the left of the middle yellow bar, it is estimated that the sound is about 66ms ahead of the picture (one frame is about 33ms).

[0005] This method has certain flaws. It can only be used to roughly estimate a delay range. If the specific delay time needs to be accurately obtained, there is a large error range. In addition, the judgment is based on the perception of the human eye and ear, which is relatively subjective and subject to individual differences. Summary of the Invention

[0006] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a technical method for measuring the relative delay between the image and sound of a DLP projector and its application.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A technical method for measuring the relative delay between the image and sound of a DLP projector comprises the following steps:

[0009] S1, by connecting the audio signal acquisition module with the signal waveform display module, using the audio signal acquisition module to collect the audio sound signal of the Bluetooth speaker, and converting it into an analog signal to be displayed on the waveform of the signal waveform display module;

[0010] S2, create a test video, the test video playback will switch from black to white;

[0011] S3, by adding 1Khz sine wave audio at the switching time point, a "beep" sound is emitted to determine the exact switching time point;

[0012] S4, using the DLP module to establish a connection between the test video and the LED driving current of the optical machine module;

[0013] S5, obtain the change trend of the LED driving current of the optical-mechanical module on the DLP module through the pure black and pure white images, and detect the LED current or voltage waveform through the signal waveform display module;

[0014] S6, by comparing the LED current or voltage waveform and the sound waveform through the signal waveform display module, the accurate picture and audio delay time can be obtained.

[0015] Preferably, the audio signal acquisition module adopts a dedicated microphone probe, and the signal waveform display module is an oscilloscope.

[0016] Preferably, the entire screen of the first half of the test video is pure black, and the entire screen of the second half of the test video is pure white.

[0017] Preferably, the transition point of the LED current or voltage waveform represents the time point when the image switches from black to white.

[0018] Preferably, the video waveform of the video signal is an LED current or voltage waveform, and the LED current or voltage waveform is a blue waveform.

[0019] Preferably, the sound waveform is a time point of an audio sound signal, and the sound waveform is a purple waveform.

[0020] Preferably, it is applied to measure the relative delay between audio and video, and can be used to set the delayed output time of the picture.

[0021] The present invention has the following beneficial effects:

[0022] Compared with the existing technology, the basic idea of ​​the present invention is to reflect the audio and picture signals simultaneously and in real time on the waveform of the oscilloscope, and accurately measure the relative delay of the audio and picture by measuring the time difference between the respective channels of the audio and picture through the oscilloscope. The present invention focuses on how to convert the video signal into a signal waveform that can be intuitively reflected in the oscilloscope. By measuring the electrical signal of the video signal processing process in the projector, it is obtained that there is a delay between each link, and the time point when the representative picture is actually displayed on the screen or projected can be obtained. Based on the above ideas, the projector of the DLP projection technology platform uses the content adaptive brightness adjustment function of the DLP technology to establish a connection between the content of a specific picture and the optical machine LED driving current. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a measured case diagram of the technical method proposed by the present invention for measuring the relative delay between the image and sound of a DLP projector.

[0024] Figure 2 Schematic diagram of the current conventional method for evaluating the relative delay between sound and picture. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0026] Reference Figure 1-Figure 2 A technical method for measuring the relative delay between the image and sound of a DLP projector comprises the following steps:

[0027] S1, by connecting the audio signal acquisition module with the signal waveform display module, using the audio signal acquisition module to collect the audio sound signal of the Bluetooth speaker, and converting it into an analog signal to be displayed on the waveform of the signal waveform display module;

[0028] S2, create a test video, the test video playback will switch from black to white;

[0029] S3, by adding 1Khz sine wave audio at the switching time point, a "beep" sound is emitted to determine the exact switching time point;

[0030] S4, using the DLP module to establish a connection between the test video and the LED driving current of the optical machine module;

[0031] S5, obtain the change trend of the LED driving current of the optical-mechanical module on the DLP module through the pure black and pure white images, and detect the LED current or voltage waveform through the signal waveform display module;

[0032] S6, by comparing the LED current or voltage waveform and the sound waveform through the signal waveform display module, the accurate picture and audio delay time can be obtained.

[0033] In the present invention, the audio signal acquisition module adopts a special microphone probe, the signal waveform display module is an oscilloscope, the first half of the test video is pure black, the second half of the test video is pure white, the jump point of the LED current or voltage waveform represents the time point when the picture switches from black to white, the video waveform of the video signal is the LED current or voltage waveform, the LED current or voltage waveform is a blue waveform, the sound waveform is the time point of the audio sound signal, and the sound waveform is a purple waveform.

[0034] The invention discloses an application of a technology for measuring the relative delay between the image and sound of a DLP projector. The technology is used to measure the relative delay between the image and sound, and can be used to set the delayed output time of the image accordingly.

[0035] The present invention can be explained through the following operation mode:

[0036] By creating a specific test video, the first half of the test video is pure black, and the second half of the test video is pure white. The video playback will switch from black to white, and 1Khz sine wave audio (a "beeping" sound) is added at the switching time.

[0037] The DLP module's content-adaptive brightness control triggers changes in the LED drive current when the screen transitions from black to white. The Signal Waveform Display Module monitors the LED current or voltage waveform during these transitions, and the transitions represent the time when the screen transitions from black to white. Simultaneously, the Audio Signal Acquisition Module captures the audio waveform from Bluetooth headphones / speakers, simultaneously obtaining the audio timing. Finally, the Signal Waveform Display Module measures the audio delay between the screen and the audio. Figure 1 This is a case measured using this method:

[0038] Figure 1 In the example, the blue waveform represents the monitored LED drive voltage waveform, and the purple waveform represents the sound waveform captured by the microphone from the Bluetooth speaker. As can be seen, when the screen switches from a full-screen black to a full-screen white, the LED voltage waveform changes (the same effect is observed for current measurement). Simultaneously, after a period of time, the sound waveform from the Bluetooth speaker is captured. This directly indicates that the audio delay relative to the image in this case is 260ms.

[0039] The above is the measurement method of the present invention. At the same time, this method is not only used for testing and evaluation, but through appropriate improvements, it can be implemented as an audio-visual synchronization function for DLP projectors. For example, after the projector is connected to a new Bluetooth headset or speaker, the system can turn on the audio-visual synchronization function, play a calibration video as described above internally (usually about 5 seconds), and then calculate the audio-visual delay through current sampling and projector microphone sampling. Then, based on the calculation result, the picture display is actively delayed to achieve the synchronization effect.

[0040] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A technical method for measuring the relative delay between the image and sound of a DLP projector, characterized in that: The following steps are involved: S1, by connecting the audio signal acquisition module with the signal waveform display module, using the audio signal acquisition module to collect the audio sound signal of the Bluetooth speaker, and converting it into an analog signal to be displayed on the waveform of the signal waveform display module; S2, create a test video, the test video playback will switch from black to white; S3, by adding 1Khz sine wave audio at the switching time, a "beep" sound is emitted to determine the exact switching time point; S4, using the DLP module to establish a connection between the test video and the LED driving current of the optical machine module; S5, obtain the change trend of the LED driving current of the optical-mechanical module on the DLP module through the pure black and pure white images, and detect the LED current or voltage waveform through the signal waveform display module; S6, compare the LED current or voltage waveform and the sound waveform through the signal waveform display module to obtain the accurate picture and audio delay time; The entire screen of the first half of the test video is pure black, and the entire screen of the second half of the test video is pure white; the DLP module includes a content-adaptive brightness adjustment function, and the jump point of the LED current or voltage waveform represents the time point when the screen switches from black to white; the video waveform of the video signal is an LED current or voltage waveform, and the content-adaptive brightness adjustment function of the DLP technology is used to establish a connection between the content of a specific screen and the optical machine LED driving current.

2. The method for measuring the relative delay between the image and sound of a DLP projector according to claim 1, characterized in that: The audio signal acquisition module adopts a dedicated microphone probe, and the signal waveform display module is an oscilloscope.

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