Jetson Linux API Reference
38.2 Release
14_multivideo_decode (multi video decode)

Overview

The multivideo_decode sample demonstrates decoding of multiple video streams in parallel. It provides options to "file write" (optional) or "video render" decoded data. Currently the application can decode a maximum of 128 streams in parallel.

Video rendering is currently disabled. You must specify the --disable-rendering command line option to avoid using this feature.

The command line option -o is optional. Use it if the user wants to dump the output file.

Supported video formats are:

  • H.264
  • H.265
  • VP8
  • VP9
  • MPEG4
  • MPEG2

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.
  • For CUDA functionality, ensure CUDA runtime is properly installed and configured.

To build

  • Enter: 
     $ cd /usr/src/jetson_multimedia_api/samples/14_multivideo_decode
 $ make

To run

  • Enter: 
     $ ./multivideo_decode num_files <number_of_files> <file_name1> <in-format1> -o <out_filename1> <file_name2> <in-format2> -o <out_filename2> --disable-rendering [options]

CUDA-specific Options

The application supports several CUDA-related command-line options:

  • -alloc_type_cplane <num>: Allocation memory type for output plane buffer
    • 0: Default (system-managed allocation)
    • 1: CUDA Pinned (host memory accessible by GPU)
    • 2: CUDA Device (GPU memory)

To view supported options

Enter: 

   $ ./multivideo_decode --help

Example

   $ ./multivideo_decode num_files 2 ../../data/Video/sample_outdoor_car_1080p_10fps.h264 H264 ../../data/Video/sample_outdoor_car_1080p_10fps.h264 H264 --disable-rendering

CUDA-enabled Example

   $ ./multivideo_decode num_files 2 ../../data/Video/sample_outdoor_car_1080p_10fps.h264 H264 ../../data/Video/sample_outdoor_car_1080p_10fps.h264 H264 --disable-rendering -alloc_type_cplane 2

This example uses CUDA Device memory for optimal GPU performance.

Flow

The following diagram shows the flow through this sample.

  • The Output Plane receives input in bitstream format and delivers it to the Decoder for decoding.
  • Decoded frames are transferred to the Capture Plane in YUV format.
  • The application transfers the decoded YUV frames to EglRenderer for rendering.
  • For the Output Plane the application supports MMAP and USRPTR memory types. For the Capture Plane it supports MMAP and DMABUF memory types.
  • The application can also dump files from the Capture Plane.
    Note
    Only MMAP is supported in output plane for Jetson Thor.

CUDA Processing Flow

It is similar to the video_decode sample , please refer to it for more details.

Key Structure and Classes

The sample uses the following key structures and classes.

Element Description
NvVideoDecoder Contains all video decoding-related elements and functions.
dec_capture_loop A pointer to the thread handler for the decoding capture loop.

The NvVideoDecoder class packages all video decoding-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.
createVideoDecoder Static function to create video decode 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 NvVideoDecoder 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.