Uncompressed video is digital video that either has never been compressed or was generated by decompressing previously compressed digital video. It is commonly used by video cameras, video monitors, video recording devices (including general purpose computers), and in video processors that perform functions such as image resizing, image rotation, deinterlacing, and text and graphics overlay. It is conveyed over various types of baseband digital video interfaces, such as HDMI, DVI, DisplayPort and SDI.
Contents
- Standalone recorders
- Recording to a computer
- Video capture interface
- Software
- Wireless transmission
- Data rates
- 422 format
- References
Some HD video cameras output uncompressed video, whereas others compress the video using a lossy compression method such as MPEG or H.264. In the compression process, some of the video information is removed, which creates compression artifacts and reduces the quality of the video when decompressed. When editing video, it is preferred to work with video that has never been compressed (or only losslessly compressed) as this maintains the best possible quality, with compression performed after completion of editing.
Standalone recorders
A standalone video recorder is a device that receives uncompressed video and stores it in either uncompressed or compressed form. These devices typically have a video output which can be used to monitor or playback recorded video. When playing back compressed video, the compressed video is uncompressed by the device before being output. Such devices may also have a communication interface, such as Ethernet or USB, which can used to exchange video files with an external computer, and in some cases control the recorder from an external computer as well.
Recording to a computer
Recording to a computer is a relatively inexpensive way to implement a digital video recorder, but the computer and its video storage device (e.g., solid-state drive, RAID) must be fast enough to keep up with the high video data rate, which in some cases may be HD video or multiple video sources, or both. Due to the extreme computational and storage system performance demands of real-time video processing, other unnecessary program activity (e.g., background processes, virus scanners) and asynchronous hardware interfaces (e.g., computer networks) may be disabled, and the process priority of the recording realtime process may be increased, to avoid disruption of the recording process.
Video capture interface
HDMI, DVI and HD-SDI inputs are available as PCI Express (partly multi-channel) or ExpressCard, USB 3.0 and Thunderbolt interface also for 2160p (4K resolution).
Software
Software for uncompressed video is often supplied with suitable hardware or available for free: Ingex (open source).
Wireless transmission
Wireless interfaces such as Wireless LAN (WLAN, Wi-Fi), WiDi, and Wireless Home Digital Interface can be used to transmit uncompressed standard definition (SD) video but not HD video because the HD bit rates would exceed the network bandwidth. HD can be transmitted using higher speed interfaces such as WirelessHD and that of the Wireless Gigabit Alliance. In all cases, when video is conveyed over a network, communication disruptions or diminished bandwidth can corrupt the video or prevent its transmission.
Data rates
Uncompressed video has a constant bitrate that is based on pixel representation, image resolution, and frame rate:
data rate = color depth * vertical resolution * horizontal resolution * refresh frequencyFor example:
4:2:2 format
The data rates and storage requirements for the widely used YCbCr 4:2:2 chroma subsampling format are listed below:
1080i and 1080p RGB (4:4:4)