35 lines
2.5 KiB
ReStructuredText
35 lines
2.5 KiB
ReStructuredText
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UVC Camera Introduction
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=======================
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:link_to_translation:`zh_CN:[中文]`
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1 Introduction to UVC
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--------------------------
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USB Video Control (UVC) is a USB device class specification in the USB industry specification, and a unified data exchange specification for video devices with USB interfaces.
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In the UVC specification, it is clearly required to have two interfaces: VC Interface (video control class Interface) and the VS Interface (video stream interface).
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The VC interface is responsible for the configuration of UVC equipment, and the VS interface is responsible for the transmission of video stream data,
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and the two cooperate with each other to complete the functions of UVC equipment. The current hardware supports USB2.0, including Full-speed and High-speed.
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In addition to the 1.5Mbps and 12Mbps transmission modes specified in USB1.1, USB2.0 also adds a high-speed transmission mode of 480Mbps.
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The USB1.1 unit data transfer time is 1 millisecond, while the USB2.0 unit data transfer time is 125 microseconds.
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The UVC output data format is determined by its own firmware, which may support H264, MJPEG, H265, etc.
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2 Types and specifications supported by UVC
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---------------------------------------------
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+-------------------+-------------------+--------------+--------------------+-----------------+------------------+-------------+--------------------+
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| USB specification | UVC specification | Transmission | transmission speed | MaxPacketSize | resolution | fps | output format |
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+===================+===================+==============+====================+=================+==================+=============+====================+
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| USB2.0 | UVC1.5/UVC1.1 | ISO/BULK | High(Full)-speed | 1024 and below |1280X720 and below| 30 and below| JPEG/H264/H265 |
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+-------------------+-------------------+--------------+--------------------+-----------------+------------------+-------------+--------------------+
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3 UVC Usage process
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------------------------
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- 1.initialize the USB hardware module, that is, initialize the host, and start its work usb_task;
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- 2.host Detects whether the device is connected and enumerates.
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- 3.After detecting that the connection is successful, the upper layer reads the device descriptor and sets UVC parameters based on it
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- 4.Start the UVC
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- 5.Process UVC packets
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- 6.Pause UVC transmission
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- 7.restore UVC transmission, etc., do a good job of state machine switching
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