Zynq UltraScale+ MPSoC VCU TRD 2019.1 - PCIe Transcode

Zynq UltraScale+ MPSoC VCU TRD 2019.1 - PCIe Transcode




Table of Contents

1 Overview

The primary goal of this Design is to demonstrate the file based VCU transcode capabilities over PCIe present in Zynq UltraScale+ EV devices.


This design supports the following interfaces:

VCU Codec:

  • Video Encode/Decode capability using VCU hard block in PL 
    • AVC/HEVC encoding.
    • Encoder/decoder parameter configuration.

Communication Interface:

  • PCIe

Video format:

  • NV12
  • NV16

Supported Resolution:

The table below provides the supported resolution from command line app only in this design.

Resolution
Command Line
Single Stream
4kp60
4kp30
1080p60
1080p30
720p30


√ - Supported
NA – Not applicable
x – Not supported


Hardware Overview

This Design uses the PCI Express (PCIe®) Endpoint block in an x4 Gen3 configuration along with DMA/Bridge Subsystem for PCI Express for data transfers between the host system memory and the Endpoint.

The DMA/Bridge Subsystem for PCI Express provides protocol conversion between PCIe transaction layer packets (TLPs) and AXI transactions. The hardware scatter-gather list (SGL) DMA interface is exercised to handle buffer management at the Endpoint to enable the memory mapped interface.

The downstream AXI4-Lite slaves include userspace registers, responsible for hand-shaking mechanism between host and the endpoint.

In the system to card direction, the DMA block moves data from the host memory to the PL-side through PCIe and then writes the data to PS-DDR via AXI-MM interface. Then VCU IP reads data from PS-DDR, performs Video encoding/decoding and writes it back to the same memory. Lastly, in card to system direction, DMA reads PS-DDR via AXI-MM interface and writes to host system memory through PCIe.

Figure 1: VCU PCIe Hardware Block Diagram

Components, Features, and Functions

4-lane integrated PCIe block with a maximum link speed of 8 GT/s (GT/s is Giga transfers per second)

  • 128-bit at 250 MHz

 DMA/Bridge subsystem for PCIe

  • AXI Memory mapped enabled
  • One of each DMA Read (H2C) & DMA write (C2H) channels

Apart from PCIe related IPs, the design contains VCU IP.


Software 

The below figure shows the PCIe software block diagram

1.1 Board Setup

Refer below link for Board Setup


1.2 Run Flow

The TRD package is released with the source code, Vivado project, Petalinux BSP, host software required for PCIe and SD card image that enables the user to run the demonstration. It also includes the binaries necessary to configure and boot the ZCU106 board. Prior to running the steps mentioned in this wiki page, download the TRD package and extract its contents to a directory referred to as ‘TRD_HOME' which is the home directory.

Refer below link to download all TRD contents.

TRD package contents are placed in the following directory structure. 

The user needs to copy all the files from the $TRD_HOME/images/vcu_pcie/ to FAT32 formatted SD card directory. 

Insert the board into the PCIe slot of the HOST machine and switch on board. Board bootup will take around 15-secs. 

HOST PACKAGE

The PCIe HOST application(pcie_host_app) will read <input .mp4 file> file data from the HOST machine and send's it to zcu106 board which is connected to HOST machine PCIe slot as endpoint device. The data received from the HOST will be decoded and encoded using VCU hardware and writes the data to the HOST machine in .ts file format. 

The files in host_package directory provides Xilinx PCIe DMA drivers, example software, to be used to exercise file transfer over the Xilinx PCIe DMA IP and perform the transcode use case using Xilinx VCU IP on zcu106 board.

Directory and file description:
===============================
- xdma/: This directory contains the Xilinx PCIe DMA kernel module driver files.

- libxdma/: This directory contains support files for the kernel driver module, which interfaces directly with the XDMA IP.

- include/: This directory contains all include files that are needed for compiling driver.

- etc/: This directory contains rules for the Xilinx PCIe DMA kernel module and software. The files in this directory should be copied to the /etc/directory on your Linux system.

- tools/: This directory contains example application software to exercise the provided kernel module driver and Xilinx PCIe DMA IP. 


Copy the hosting package on to UBUNTU-14.04 machine and run the below commands to Install the XDMA driver and compile the host transcode application.

NOTE: Root permissions will be required to install xdma driver.

The Host software consists of XDMA module with the following user access devices. 

 xdma0_control : to access XDMA registers

 xdma0_xvc : to access userspace registers from HOST

 xdma0_user : to access AXI-Lite Master interface

 xdma0_bypass : to access DMA-Bypass interface

 xdma0_h2c_0, xdma0_c2h_0: to access each channel


HOST APPLICATION

Run the below command to initiate a file transfer from the HOST machine and transcode it from the ZCU106 device. After running the application on HOST user need to start device application(pcie_transcode) on the zcu106 target to initiate the transfer.


The user was given with the below options for transcoding the file : 

DEVICE APPLICATION

After booting the ZCU106 board with the SD images, to run the transcode use case first run the host side application mentioned as above and run the device application on the zcu106 device with the mentioned commands below. The host application will send file data to the device for transcoding it on the ZCU106 device and receives the transcoded data and saves it on to the host machine.


1.3 Build Flow

Refer below link for Build Flow

Zynq UltraScale+ MPSoC VCU TRD 2019.1 - Run and Build Flow


2 Other Information

2.1 Known Issues

2.2 Limitations

  • For playback in DP, video input resolution should match to DP's native resolution. This constraint is due to support of GUI. In GUI case if we allow video source other than native resolution(by setting fullscreen overlay) then graphics layer will disappear. To recover back GUI user need to kill and relaunch the GUI app. To avoid such condition TRD only supports video input resolution which is equal to DP's native resolution.
  • For VCU related limitations please refer AR# 72293: PetaLinux 2019.1 - Product Update Release Notes and Known Issues and PG252 link.

2.3 Optimum VCU Encoder parameters for use-cases:

Quality: Low bitrate AVC encoding:

  • Enable profile=high and use qp-mode=auto for low-bitrate encoding use-cases.
  • The high profile enables 8x8 transform which results in better video quality at low bitrates.