Autor: Alexander Eichhorn

Input and Output (I/O)

High-performance I/O is a key component for an efficient media production workflow.

There are multiple competing industry standards for connecting professional and consumer hardware to general purpose computers.

An I/O standard defines physical connector dimensions, electrical signals and digital protocols to exchange data. As standards evolve, higher data rates are added and new connector types may be defined. Today, all digital standards are designed to be future-proof, that means devices are forward-compatible across at least two generations (i.e. running a new device on a previous-generation host).

I/O terminology talks about hosts and devices, where computers are referred to as hosts and all externally connected I/O components are devices. Some I/O standards allow daisy-chaining of devices and support hubs to attach multiple devices to a single host connector. In some standards the host can also deliver power (e.g. USB, Thunderbolt) .


Universal serial bus (USB) is a bi-directional hot-pluggable I/O standard for connecting and powering low-speed computer peripherals such as keyboards, pointing devices, and printers and high-speed devices such as digital cameras, disk drives, audio and video signal converters, network adapters and more. Introduced in 1996, USB has gone through major revisions and supports very high-speed connections up to 10 Gbit/s full-duplex (USB3) today. A characteristic of USB used to be that connector cables have two distinct connectors, a host-facing and a device-facing connector. The most recent USB Type-C changed this by introducing a smaller reversible plug connector and also made the cables active, meaning they now contain an ID chip signalling the cable configuration to the host.


Thunderbolt is a novel I/O standard developed by Intel in 2011 which combines PCI Express and DisplayPort for external computer peripherals (mainly displays and hard disks). Thunderbolt is bi-directional, provides power and lets you connect up to 6 devices to one host connector in different topologies (hubs and daisy-chaining). Thunderbolt 1 and 2 used the same connector as Mini DisplayPort, while Thunderbolt 3 started using the same connector as USB Type-C. Thunderbolt is interoperable with DisplayPort, which means when you connect a DP enabled device a Thunderbolt host will provide a native DP signal.


DisplayPort is the first digital display interface that uses packetized data transmission for a greater flexibility and image quality. DisplayPort can carry video, audio and auxilliary data signals. The video signal can consist of a single or multiple video streams with 6 to 16bit per component in multiple color spaces (e.g. sRGB, BT.601, BT.709, DCI-P3) and unlimited resolution up to bandwidth capacity. Audio is supported with up to 8 channels, 16 or 24-bit linear PCM at 32 to 192 kHz sampling rate. DisplayPort is mainly uni-directional, with the exception of a bi-directional, half-duplex auxiliary data channel with up to 720 Mbit/s (DP1.2) which can be used for device management and control (a bi-directional USB channel is available too). Most DP graphics cards support dual-mode DisplayPort (DP++) which can also emit single-link DVI and HDMI 1.4 signals through passive adapters. Starting with DP 1.3 HDMI 2.0 is supported as well. The data rate of DP 1.3 is sufficient for a 4K UHD display (3840×2160) at 120Hz, a 5K display (5120×2880) at 60Hz, or an 8K UHD display (7680×4320) at 30Hz, with 24-bit RGB color.


High-Definition Multimedia Interface (HDMI) is a consumer-oriented I/O interface for uni-directionally transmitting uncompressed digital video and digital audio to displays and audio devices. More recent versions add return and device control channels. HDMI is based on the EIA/CEA-861 standard family and signals are backwards-compatible with single-link DVI. sRGB color space at 8 bits per component is mandatory for HDMI devices, while other color spaces (xvYCC, YCbCr) and higher color depths (10-16bit) are optional. HDMI allows up to 8 channels digital audio either PCM stereo up to 24bit 192kHz (mandatory) or compressed Dolby Digital, DTS, DVD Audio and Super Audio CD. HDMI 2.0 supports 4K UHD at 60Hz and optionally Rec.2020 the color space, HDMI 2.0a adds HDR support.

I/O Performances Overview

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