01_video_encode

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

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Overview

The video_encode sample application demonstrates how to encode H.264/H.265 video streams.

The application YUV reads input buffers from a file, performs H.264 or H.265 video encoding, and saves the encoded bitstream to an elementary .264 or .265 file.

The application runs on file source simulated input buffers, and so does not require a camera.

Supported video formats are:

• H.264
• H.265

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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.

To build

• Enter:

   $ cd $HOME/multimedia_api/samples/01_video_encode
   $ make
  

To run

• Enter:

  $ video_encode <in-file> <in-width> <in-height> <encoder-type> <out-file> [OPTIONS]
  

To view supported options

Enter:

   $ ./video_encode --help

Example

   $ ./video_encode ../../data/Video/sample_outdoor_car_1080p_10fps.yuv 1920 1080 H264 sample_outdoor_car_1080p_10fps.h264

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Flow

The following diagram shows the flow through this sample.

• The Output Plane receives input in YUV frame format and delivers it to the Encoder for encoding.
• The Capture Plane transfers encoded frames to the application in bitstream format.
• The encoded bitstream is written to a file.
• For the Output Plane the application supports MMAP, DMABUF, and USRPTR memory types. For the Capture Plane it supports MMAP memory type.

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Key Structure and Classes

The sample uses the following key structures and classes.

Element	Description
NvVideoEncoder	Contains all video encoding-related elements and functions.
Enc_pollthread	A pointer to the thread handler for the encoding capture loop.

The NvVideoEncoder class packages all video encoding-related elements and functions. Key members used in the sample are:

Member	Description
output_plane	Specifies the V4L2 output plane.
capture_plane	Specifies the V4L2 capture plane.
createVideoEncoder	Static function to create video encode object.
subscribeEvent	Subscribe event.
setOutputPlaneFormat	Set output plane format.
setCapturePlaneFormat	Set capture plane format.
dqEvent	Dqueue the event which reports by the V4L2 device.
isInError	Checks if under error state.

Class NvVideoEncoder contains two key elements: output_plane and capture_plane. These objects are derived from class type NvV4l2ElementPlane. The sample uses the following key members:

Element	Description
setupPlane	Sets up the plane of V4L2 element.
deinitPlane	Destroys the plane of the V4L2 element.
setStreamStatus	Starts/stops the stream.
setDQThreadCallback	Sets the callback function of the dqueue buffer thread.
startDQThread	Starts the thread of the dqueue buffer.
stopDQThread	Stops the thread of the dqueue buffer.
qBuffer	Queues the V4L2 buffer.
dqBuffer	Dequeues the V4L2 buffer.
getNumBuffers	Gets the number of V4L2 buffers.
getNumQueuedBuffers	Gets the number of buffers currently queued on the plane.