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Low Latency, Highly Reliable Wireless Video Transmission to iPad

Institute of Embedded Systems, a research institute of Zurich University of Applied Sciences generated a reference design for a low latency, highly reliable wireless video transmission from a battery operated camera to an iPad or iPhone. The design is suitable for everything that requires a robust low latency video link such as vehicle remote control, industrial applications, automotive applications and others. Since the transmission is Wi-Fi based, no extra hardware to receive the video stream on an iPad or iPhone is required.
The camera module consists of an Intel SoC-FPGA with integrated single core ARM-A9 with flexible interface to various types of cameras and SDIO interface to the Wi-Fi module. Optional LCD interfaces or an SD-card slot allow monitoring and recording of the video at the camera module.


The low latency video compression algorithm is nearly lossless and always transmits full frames. While the compression is implemented in the FPGA fabric, control is accomplished by a Linux operating system in the ARM-A9.
Error correction avoids pixel and frame drops even if Wi-Fi transmission is problematic, like in busy areas or in difficult topography. The Wi-Fi standard includes automatic retransmission of lost packets. However, there still remains a chance that packets are lost. To increase reliability even further, we add redundant packets. This slightly increases the bandwidth however does not add significant latency.
To receive the video stream, it is enough to install a viewer app, no extra hardware is required. Video decompression and error correction are solely handled in the GPU and the CPU of the iPad.
The FPGA IP requires only 2.9k logic cells, which is 18% of a 15k logic cell Intel Cyclone-V SoC.
The transmitter IP controls an 802.11n Wi-Fi module like the Texas Instruments WL1835MOD, however other TI modules are supported as well.
The measured glass to glass latency can be as low as 65 ms (2 video frames at 30 fps). However, dependent on the selected compression rate and the Wi-Fi channel quality, the latency might be higher.
For more information, contact

Audio Video Regression Test System

For our test driven way of development we build up a regression test system for our high performance video and audio transmission. The system is used to schedule and run tests and monitor the results in real time. For this, it provides a wide range of interfaces to interact with the system under test. This includes interfaces to monitor and manipulate the network traffic as well as interfaces to generate and analyse video and audio signals.



The system is based on a Linux OS and can therefore be used on many different hardware platforms. The tests to be run are written in Python and can be run automatically or manually. An interface to Jenkins allows to combine the test system with the build flow.

The regression test system provides following advantages:

 – Improved quality due to regression testing

 – Automation of the testing process

 – Simplification of the test implementation

 – Individual adaptions depending on the test dependencies

Improved quality due to regression testing

With regression tests is the system tested with a large number of test cases. Some of the cases are based on the expected behavior of the system. Some cases are based on reports from customers and partners. Before a new software is released it has to pass all this test cases. Like this, each release provides at least as good as the last one and the software will continuously improve with each release.


Automation of the testing process

The InES regression test system provides an interface to Jenkins. This allows to include the tests directly into the build flow. The newest software can be built and downloaded to the target system. Which is then tested with all the regression test cases. The Jenkins web interface allows the user always to see the current progress as well as to change or interrupt some steps if required.

Simplification of the test implementation

The InES regression test systems provides the required interfaces to the device under test as well as the tools to schedule and execute the tests. The user just has to describe the test cases in Python. The test system can be set up on a PC or embedded system. It is also possible to split the test system over multiple platforms.

Individual adaptions depending on the test dependencies

The regression test system is built up modular. It’s possible to deactivate unused interfaces to reduce the requirements for the platform. It is also possible to add new interfaces specifically adapted to the device under test. Like this, it’s possible to adapt the test system perfectly to the device under test as well as to the platform it runs on.

HDMI Real-Time Analyzer and Tester

The High-Performance Multimedia Group has developed an HDMI Real-Time Analyzer and Tester which allows logging and real-time modifications of the HDMI stream between source and sink.


  • Compliance testing of HDMI devices
  • Simulating non-compliant communication behavior to test your device’s robustness




  • User-defined insertion and simulation of Enhanced Extended Display Identification Data (E-EDID) communication
  • Automatic simulation of several HDMI devices in a batch testing-procedure
  • Real-time modification of HDMI communication-stream, such as corrupting or delaying the responses of HDMI devices.
  • Logging of DDC communication
  • Real-time image analysis for automated testing

The HDMI Real-Time Analyzer and Tester is implemented on an Altera FPGA with NIOS II softcore processor running Linux. The device taps into the DDC channel to allow logging and modifying the communication in real-time according to user-defined behavior rules.  

Open source driver for HDMI2CSI module released


The open source driver for the HDMI2CSI Interface (HDMI2CSI)  are now available at The driver was developed within the Video4Linux2 (V4L2) framework and consists of three main components:

  • A host driver for controlling the Video Interface (VI2) on the Nvidia Jetson TX1 host processor
  • A subdevice driver that interacts with the Toshiba TC358840 CSI-HDMI bridge IC
  • A video buffer driver

The driver supports standard device tree and currently runs on the Linux4Tegra (L4T) R24.1 operating system.  The video stream can be accessed from user space using GStreamer, the versatile multimedia framework.

Fig.1: Hardware and software components for using HDMI2CSI with a Nvidia Jetson TX1 host processor

Documentation containing instructions about how to employ the drivers for the HDMI2CSI module are available at

Embedded Computing Conference


Embedded Computing Conference

Meet us at the Embedded Computing Conference on May 31st on the Campus of  ZHAW School of Engineering, Technikumstrasse 9, 8401 Winterthur. We are presenting new technology highlights based on embedded processors with integrated GPU.

4K HDMI to CSI Interface for TX1 Evalboard

The High-Performance Multimedia Group has developed a High Definition Multimedia Interface (HDMI®) to MIPI®Camera Serial Interface Type 2 (CSI-2) converter module (HDMI2CSI) as a plug in to the NVIDIA Jetson TX1 development kit.
The HDMI2CSI module supports 4K video resolution for next-generation embedded Ultra High Definition video applications. The HDMI2CSI module offers two 4K/2K HDMI video and audio streams to be simultaneously converted in MIPI CSI-2 video and TDM audio format that can be processed by the Jetson TX1 processor.
The Jetson TX1 board is equipped with 3 four-lanes MIPI high-speed camera serial interfaces (CSI-2) which are used by the HDMI2CSI board to input HDMI video. The module utilizes two MIPI CSI-2 ports of the Jetson TX1 board (8 lanes) to input a 4K HDMI video stream. For a second 2K HDMI video stream, the remaining MIPI CSI-2 port is used (4 lanes).
Eight channels of HDMI audio streams per HDMI input are also supported and can be transmitted over TDM or I2S.
4K capable drivers for the HDMI2CSI are available as open source.



Fig. 1: The HDMI2CSI Board




Fig. 2:  The HDMI2CSI Board attached to the NVidia TX1 Evaluation Board


Technical Data:

  • Based on Toshiba TC358840 Camera Serial Interface converter ICs
  • HDMI 1.4b
  • 4096 x 2160 (4Kx2K) @ 24 fps
  • 3840 x 2160, @ 30 fps
  • 4 x I2S Audio Interface with 16, 18, 20 or 24-bit
  • 8 Channel TDM (Time Division Multiplexed Audio Interface) with 16, 18, 20 or 24-bit
  • HDCP 1.4 support
  • EDID support via I2C

For purchasing orders please contact Pender Electronic Design


(c) ZHAW Institute of Embedded Systems

Blog is online

Welcome to the new High-Performance Multimedia Blog. Our research group is part of the Institute of Embedded Systems (InES)  at the Zurich University of Applied Sciences (ZHAW). Our main activities are Audio/Video processing and data acquisition systems. We are involved in a number of different projects with industry partners in medical, professional video and audio, high-speed signal analysis as well as other research domains.

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