Zynq UltraScale+ MPSoC VCU TRD 2022.2 - Xilinx Low Latency PL DDR HDMI Video Capture and Display

This page provides all the information related to Design Module 12 - VCU TRD Xilinx low latency (LLP2) PL DDR HDMI Video Capture and Display design.

Table of Contents

1 Overview

This module enables capture of video from an HDMI-Rx subsystem implemented in the PL. The video can be displayed through the HDMI-Tx subsystem implemented in the PL. The module can stream-out and stream-in live captured video frames through an Ethernet interface at ultra-low latencies using Sync IP. This module supports four video streams using AXI broadcaster at capture side and mixer at display side for NV16 and XV20 pixel format. In this design PL_DDR is used for decoding and PS_DDR for encoding so that DDR bandwidth would be enough to support high bandwidth VCU applications requiring simultaneous encoder and decoder operations and transcoding at 4k @60 FPS.

The VCU encoder and decoder operate in slice mode. An input frame is divided into multiple slices (8 or 16) horizontally. The encoder generates a slice_done interrupt at every end of the slice. Generated NAL unit data can be passed to a downstream element immediately without waiting for the frame_done interrupt. The VCU decoder also starts processing data as soon as one slice of data is ready in its circular buffer instead of waiting for complete frame data. The Sync IP does an AXI transaction-level tracking so that the producer and consumer can be synchronized at the granularity of AXI transactions instead of granularity at the video buffer level. Sync IP is responsible for synchronizing buffers between Capture DMA and VCU encoder as both work on same buffer.

The capture element (FB write DMA) writes video buffers in raster-scan order. SyncIP monitors the buffer level while the capture element is writing into DRAM and allows the encoder to read input buffer data if the requested data is already written by DMA, otherwise it blocks the encoder until DMA completes its writes. On the decoder side, the VCU decoder writes decoded video buffer data into DRAM in block-raster scan order and displays reads data in raster-scan order. To avoid display under-run problems, software ensures a phase difference of "~frame_period/2", so that decoder is ahead compare to display.

This design supports the following video interfaces:

Sources:

  • HDMI-Rx capture pipeline implemented in the PL.

  • Stream-In from network or internet.

Sinks:

  • HDMI-Tx display pipeline implemented in the PL.

VCU Codec:

  • Video Encode/Decode capability using VCU hard block in PL.

    • AVC/HEVC encoding

    • Encoder/decoder parameter configuration.

Video formats:

  • NV16

  • XV20

Supported Resolutions:

The table below provides the supported resolutions for this design.

Resolution

Command Line

Single Stream

Multi-stream

4kp60

NA

4kp30

√ (Max 2)

1080p60

√ (Max 4 for encoder) (Max 2 for decoder)

√ - Supported
NA – Not applicable
x – Not supported

When using Low Latency mode (LLP1/LLP2), The encoder and decoder are limited by the number of internal cores. The encoder has a maximum of four streams and the decoder has a maximum of two streams.

The below table gives information about the features supported in this design.

Pipeline

Input source

Format

Output Type

Resolution

VCU codec

Pipeline

Input source

Format

Output Type

Resolution

VCU codec

Serial pipeline (Capture -> Encode -> Decode -> Display)

HDMI-Rx

NV16/XV20

HDMI-Tx

4kp60/4kp30/1080p60

HEVC/AVC

Stream-Out pipeline (Capture -> Encode -> Stream-out)

HDMI-Rx

NV16/XV20

Stream-Out

4kp60/4kp30/1080p60

HEVC/AVC

Stream-in pipeline (Stream-in -> Decode -> Display)

Stream-In

NV16/XV20

HDMI-Tx

4kp60/4kp30/1080p60

HEVC/AVC

The below figure shows the Xilinx Low Latency PL DDR HDMI Video Capture and Display design hardware block diagram.

The below figure shows the Xilinx Low Latency PL DDR PLDDR HDMI Video Capture and Display design software block diagram.

1.1 Board Setup

Refer to the below link for Board Setup

1.2 Run Flow

The TRD package is released with the source code, Vivado project, PetaLinux BSP, 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.

TRD package contents are placed in the following directory structure. The user needs to copy all the files from the $TRD_HOME/images/vcu_llp2_plddr_hdmi/ to FAT32 formatted SD card directory.

rdf0428-zcu106-vcu-trd-2022-2/ ├── apu │   └── vcu_petalinux_bsp ├── images │   ├── vcu_audio │   ├── vcu_llp2_hdmi_nv12 │   ├── vcu_llp2_hlg_sdi │   ├── vcu_llp2_plddr_hdmi │   ├── vcu_multistream_nv12 │   ├── vcu_plddrv1_hdr10_hdmi │   ├── vcu_plddrv2_hdr10_hdmi │   └── vcu_yuv444 ├── pl │   ├── constrs │   ├── designs │   ├── prebuild │   ├── README.md │   └── srcs ├── README.txt └── zcu106_vcu_trd_sources_and_licenses.tar.gz 16 directories, 3 files

TRD package contents specific to VCU Xilinx Low Latency PL DDR HDMI design are placed in the following directory structure.

rdf0428-zcu106-vcu-trd-2022-2 ├── apu │   └── vcu_petalinux_bsp │   └── xilinx-vcu-zcu106-v2022.2-final.bsp ├── images │ ├── vcu_llp2_plddr_hdmi │ │ ├── autostart.sh │   │   ├── BOOT.BIN │   │   ├── bootfiles/ │   │   ├── boot.scr │   │   ├── config/ │   │   ├── Image │   │   ├── rootfs.cpio.gz.u-boot │   │   ├── system.dtb │   │   └── vcu/ ├── pl │ ├── constrs/ │ ├── designs │ │ ├── zcu106_llp2_xv20_nv16/ │ ├── prebuild │ │ ├── zcu106_llp2_xv20_nv16/ │ ├── README.md │ └── srcs └── README.txt └── zcu106_vcu_trd_sources_and_licenses.tar.gz

Configuration files(input.cfg) for various resolutions are placed in the following directory structure in /media/card.

  • As llp2 stream-in is not supported with vcu-gst-app, we have added sample shell scripts containing relevant GStreamer commands for all Stream-in use-cases. User can modify the scripts as per convenience, or can directly use GStreamer pipelines provided in this wiki page.

  • For 4x1080p60 display use-case, we have added sample shell scripts containing relevant GStreamer commands for all Display use-cases. User can modify the scripts as per convenience, or can directly use GStreamer pipelines provided in this wiki page.

config/ ├── 1-4kp60 │   ├── Display │   ├── Stream-in │   └── Stream-out ├── 2-1080p60 │   ├── Display │   ├── Stream-in │   └── Stream-out ├── 2-4kp30 │   ├── Display │   ├── Stream-in │   └── Stream-out ├── 4-1080p60 │   ├── Display │   ├── Stream-in │   └── Stream-out └── input.cfg

1.2.1 GStreamer Application (vcu_gst_app)

The vcu_gst_app is a command line multi-threaded Linux application. The command line application requires an input configuration file (input.cfg) to be provided in the plain text.

Run below modetest command to set CRTC configurations for 4kp60:

Run below modetest command to set CRTC configurations for 4kp30:

Execution of the application is shown below:

Example:

  • Make sure HDMI-Rx should be configured to 4kp60 mode, while running below example pipelines.

  • Low latency(LLP1/LLP2) stream-in pipelines are not supported in vcu_gst_app.

4kp60 XV20/NV16 HEVC_25Mbps ultra low-latency(LLP2) display pipeline execution.

4kp60 XV20/NV16 HEVC_25Mbps ultra low-latency(LLP2) stream-out pipeline execution.

4kp60 XV20/NV16 HEVC ultra low-latency(LLP2) stream-in pipeline execution.

OR

For LLP1/LLP2 Multi-stream HEVC serial and stream-out use-cases (2-4kp30, 2-1080p60, 4-1080p60), use ENC_EXTRA_OP_BUFFERS=10 variable before vcu_gst_app command. Below is the sample pipeline:

To measure the latency of the pipeline, run the below command. The latency data is huge, so dump it to a file.

Refer to the below link for detailed run flow steps:

1.3 Build Flow

Refer to the below link for detailed build flow steps:


2 Other Information

2.1 Known Issues

2.2 Limitations

2.3 Optimum VCU Encoder parameters for use-cases

Video streaming:

  • Video streaming use-case requires very stable bitrate graph for all pictures.

  • It is good to avoid periodic large Intra pictures during the encoding session

  • Low-latency rate control (hardware RC) is the preferred control-rate for video streaming, it tries to maintain equal amount frame sizes for all pictures.

  • Good to avoid periodic Intra frames instead use low-delay-p (IPPPPP…)

  • VBR is not a preferred mode of streaming.

Performance: AVC Encoder settings:

  • It is preferred to use 8 slices only for better AVC encoder performance.

  • AVC standard does not support Tile mode processing which results in the processing of MB rows sequentially for entropy coding.

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.


3 Appendix A - Input Configuration File (input.cfg)

The example configuration files are stored at /media/card/config/ folder.

Configuration Type

Configuration Name

Description

Available Options

Note

Configuration Type

Configuration Name

Description