Wikipedia

Uncompressed video

Uncompressed videoisdigital videothat either has never beencompressedor 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 asHDMI,DVI,DisplayPortandSDI.Standards also exist for the carriage of uncompressed video overcomputer networks.

SomeHD videocameras output uncompressed video, whereas others compress the video using a lossy compression method such asMPEGorH.264.In any lossy compression process, some of the video information is removed, which createscompression artifactsand reduces the quality of the resulting decompressed video. When editing video, it is preferred to work with video that has never been compressed (or was losslessly compressed) as this maintains the best possible quality, with compression performed after completion of editing.[1]

Uncompressed video should not be confused withraw video.Raw video represents largely unprocessed data (e.g. withoutdemosaicing) captured by an imaging device.

Recording

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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 that 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 is a relatively inexpensive alternative to implementing 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 beHD videoor multiple video sources, or both. Due to the extreme computational and storage system performance demands of real-time video processing, other unnecessaryprogramactivity (e.g.,background processes,virus scanners) and asynchronous hardware interfaces (e.g.,computer networks) may be disabled, and theprocess priorityof the recordingrealtime processmay be increased, to avoid disruption of the recording process.

HDMI, DVI and HD-SDI inputs are available asPCI Express(partly multi-channel) orExpressCard,USB 3.0[2]andThunderboltinterface[3][4][5]also for2160p(4K resolution).[6][7]

Software for recording uncompressed video is often supplied with suitable hardware or available for free e.g.Ingex.[8]

Network transmission

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SMPTE 2022and2110are standards for professional digital video overIP networks.SMPTE 2022 includes provisions for both compressed and uncompressed video formats. SMPTE 2110 carries uncompressed video, audio, andancillary dataas separatestreams.

Wireless interfacessuch asWireless LAN(WLAN,Wi-Fi),WiDi,andWireless Home Digital Interfacecan 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 asWirelessHDandWiGig.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

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Uncompressed video has aconstant bitratethat is based on pixel representation, image resolution, and frame rate:

data rate=color depth[a]× verticalresolution× horizontal resolution ×refresh frequency[citation needed]

For example:

  • 16-bit, 480i @ 24fps:16 ×640 × 240[b]× 24 = 58.9Mbit/s
  • 24-bit, 480p @ 30 fps: 24 ×640 × 480× 30 = 221 Mbit/s.
  • 24-bit, 720p @ 30 fps: 24 ×1280 × 720× 30 = 663 Mbit/s.
  • 24-bit, 720p @ 60 fps: 24 ×1280 × 720× 60 = 1.32Gbit/s
  • 24-bit, 1080i @ 60 fps: 24 ×1920 × 540× 60 = 1.49 Gbit/s.
  • 24-bit, 1080p @ 60 fps: 24 ×1920 × 1080× 60 = 2.98 Gbit/s.
  • 24-bit,4K UHD@ 60 fps: 24 ×3840 × 2160× 60 = 11.9 Gbit/s.
  • 24-bit, 4K UHD @ 120 fps: 24 ×3840 × 2160× 120 = 23.8 Gbit/s.
  • 48-bit,DCI 4K@ 144 fps: 48 ×4096 × 2160× 144 = 61.1 Gbit/s.

The actual data rate may be higher because some transmission media for uncompressed video require definedblanking intervals,which effectively add unused pixels around the visible image.

See also

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Notes

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  1. ^Most of the time color depth can be calculated as 3 × single color depth. For example, values of a single color can be represented with a range from 0 to 255 (8 bits) which gives a total color depth as 3 × 8 = 24.
  2. ^Interlaced videoformats transmit every other line, half the picture content, per field period. Two fields are required for a full frame so the vertical resolution is halved in this calculation.

References

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  1. ^Using Uncompressed Audio and Video StreamsMicrosoft
  2. ^Compare USB Video GrabbersEpiphan
  3. ^Intensity modelsBlackmagic
  4. ^HD-SDI Express/34Imperx
  5. ^OEM video card for 8-10-12-bit HD-SD SDI digital video to PCI ExpressDeltacast
  6. ^Capture Card SeriesMagewell
  7. ^DeckLink modelsBlackmagic
  8. ^Ingex Studio - Multi-camera Tapeless Recording
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