camera_unit_sample (capture with libv4l2_nvargus)

• Overview
• Building and Running
• Flow
• Key Structure and Classes

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Overview

The camera_sample application is a unit level implementation to demonstrate the use of libv4l2_nvargus interface for streaming.

The application reads the captured buffers for either EGL renderer to preview or dump the raw buffers into a file without any extra memory copy.

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Building and Running

Prerequisites

• You have followed steps 1-3 in Building and Running.
• If you are building from your host Linux PC (x86), you have followed step 4 in Building and Running.
• You have a camera.

To build

• Enter:

   $ cd /usr/src/jetson_multimedia_api/samples/unittest_samples/camera_unit_sample
   $ make
  

To run

• Enter:

  $ ./camera_sample [OPTIONS]
  

The captured preview stream can display over HDMI.

Example

   $ ./camera_sample -r 1920 1080 -fps 30 1

To view supported options

   $ ./camera_sample -h

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Flow

The following diagram shows the flow through this sample.

• The v4l2 libargus instance is created.
• Capture Plane is set up.
• External controls are set.
• Buffers are allocated.
• Empty buffers are queued on Capture Plane.
• The Capture Plane transfers the frames to the application in raw YUV format.
• The buffers are rendered and can also be written to a file.
• For the Capture Plane the application supports MMAP and DMABUF memory type.

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Key Structure and Classes

The sample uses the following key class and structures:

Element	Description
Buffer	Class modeled on v4l2_buffer structure.

Classes	Description
class NvEGLRender	The class contains elements and functions to render frames to EGL window.

NvEGLRender is the class that packages all the functions for video rendering. Key members used in the sample are as follows:

NvEGLRender	Description
NvEglRenderer::render	Render the FD to an EGL window.

The key structures and functions used in the sample are:

Function	Description
dq_buffer	Dequeues a buffer from the plane.
capture_plane_callback	DQ Callback function.
q_buffer	Queues a buffer on the plane.
req_buffers_on_capture_plane	Request buffers on the encoder capture plane.
set_plane_format	Set format on the encoder capture plane.
set_controls	Set values of Argus properties and controls.