Way of storing images.

YCbCr is a component color space used by most digital video tape recorders to record video to tape. Unlike the RGB model, YCbCr breaks the visual information into black and white (luma) signal and two color components.

Practical implementations of YCbCr take into account that human eye is less sensitive to color stimulus than black and white stimulus reduce the amount of information contained by color components.

For example, D5 VTR utilizes 4:2:2 color subsampling which means there is only half as much color information as black and white information.

YCbCr is a color space related but not equivalent to YUV color space.

Synchronizing signal for HD equipment.

Similar to black burst in standard definition equipment, tri-level sync is the signal which provides heartbeat to high definition equipment. The purpose of the signal is to synchronize various pieces of video and audio equipment so they may work in concert with each other.

Tri-level sync is generated by a sync generator and distributed to various pieces of equipment throughout the facility. It is necessary to provide proper tri-level sync for each of HD standards. For example a single signal can not be fed to both equipment working in 1080 59.94i and 720 59.94p standards.

In certain situations it is possible to use the old fashioned black burst in place of tri-level sync.

You may not see much difference on a small size screen.

Have you ever wandered what’s the big deal about expensive digital cameras because your cheap point-and-shoot camera produces the same quality photos when viewed in an email attachment? If all you’re going to do is email small size photos, a cheap camera will do a decent job. However, if you decide to do an 8×10 enlargement of the same image you will see many shortcomings when compared to a 6 megapixel camera.

The exact same “science” applies to high def. When you compare SD originated image to HD image on a small size monitor you may not be able to appreciate the amount of information contained within the HD signal. The difference becomes more noticeable with increase in TV size. At about 28″ diagonal most people will react favorably to HD.

TV manufacturers have responded to the trend of larger screen size which has been particularly accelerated by the drop in prices of large screen LCD monitors and TVs. Average TV screen size in the U.S. is 38″.

Way of storing images.

RGB stands for Red, Green and Blue. The acronym can mean many thing but in context of high and standard definition television it almost exclusively addresses image storage and processing in digital format.

Storing images using the color primaries is as old as color photography and can be emulated digitally. In digital realm RGB takes advantage of a physical phenomenon called additive mixing. When color primaries such as red, green and blue are added in equal amounts white light is created. The white color coming off your computer screen is really a mixture of red, green and blue which can be easily verified with a magnifying glass. Varying the percentages of the three primaries creates other hues and values.

RGB is just one of color models used in TV and photographic imaging.

Just the way it is.

Why would anyone want NTSC video to run at 29.97 frames per second? What about HD video running not at 24 frames per second but at 23.98 frames per second?

It wasn’t intended that way. Before introduction of NTSC color North American television ran at true 30fps. The addition of color had to overcome a significant obstacle. No black and white TVs were to be left in the dark. The new color system had to be backwards compatible with the old black and white system.

This posed a significant challenge. For a set of very specific reasons that have to do with physics of radio transmission the frame rate of television had to be slowed down a minute amount to 29.97fps.

HDTV radio transmission is not bound by the same constraints that once necessitated slowing down of standard definition television rate. HD in North America runs at either 23.98fps, 29.97fps (also known as 59.94i) or 59.94fps for another reason.

HD non-integer frame rates have been devised in order to accommodate easy downconversion to SD. Downconverting from 30fps to 29.97fps is a tough proposition. It makes perfect sense for HD to run at either 24fps, 30fps or 60fps but as long as there is a need to downconvert to SD or use legacy video equipment integer frame rates are not going to be feasible.

Watch for incompatibility between platforms.

Material Exchange Format (MXF) is a digital video and audio container format. Manufacturers like Sony, Avid, Apple and Panasonic use MXF format for media recording. Although MXF was designed to provide maximum compatibility between different platforms different manufacturers have implemented the format in various ways causing a lack of compatibility.

The key word is “container” format. An MXF container will be read by any device that supports MXF but it may not necessarily know what to do with the contents. If attempting to use MXF between platforms of different manufacturers as a part of your workflow make sure you conduct tests before starting the job.

Film timecode and more.

Keykode (not keycode) is an addressing system for motion picture film. It is recorded as barcode on the edge of the film. It contains the film manufacturer ID, batch and roll number and footage counter.

Keykode allows precise location of any frame of film for purposes of negative cutting, scanning or telecine transfer. Keykode metadata is typically stored in digital film scans so every frame of film can be traced back to the negative. Telecine transfer to tape can also generate files which link the newly created tapes to their respective film negatives.

Fig. 1. Keykode is Printed Along the Edge of the Film

“i” stands for “interlaced” and “p” for “progressive”

There are technical as well as aesthetic differences between the two. Progressive is easier to grasp.

In progressive format each frame is intact, discreet and represents one sample in time. When you freeze a progressive frame it looks clean much the same way a frame of motion picture film would. In fact the analogy with film goes a step further. Some progressive formats are shot at roughly 24 frames-per-second (fps) making a migration from tape to film a relatively straightforward process as far as temporal issues are concerned.

Interlaced formats mimic SD video. Each frame displays two fields when frozen. Fields represent two discreet samples in time. Any fast motion in frame will render the two fields clearly distinct. The fields are interlaced together like crossed fingers of two hands but not until they reach the display and sometimes not until they reach our brains. Interlaced video at 29.97fps in North America (sometimes erroneously labeled NTSC) displays 59.94 interlaced fields per second.

The difference between the two is obvious to a casual viewer although he or she may not be able to describe it well. Interlaced video in North America has roughly 2.5 times finer rendition of motion than progressive video shot at 23.98fps. Ironically, this advantage is what most people discount as “non-cinematic” look of video.

We are culturally conditioned to accept the look of 23.98fps as the look of dramatic narrative entertainment. Interlaced look is the one we often associate with immediacy of TV news or sports telecasts.

Your network will have the final say on “i” or “p.” It is very important to determine the delivery HD standard before choosing cameras. While it is easier to convert from progressive material to interlaced, conversions from interlaced to progressive generally lack quality and may not be acceptable by your network.

A consumer equipment interface of interest to professionals.

HDMI (High Definition Multimedia Interface) is a consumer video/audio equipment uncompressed, all-digital interface. HDMI is used to connect any audio/video source, such as a set-top box, DVD player, or A/V receiver and/or video monitor over a single cable.

HDMI supports standard, enhanced, or HD video, plus multi-channel digital audio on a single cable. It has recently been gaining ground as an inexpensive alternative to HD SDI for capture and playback to and from HDV cameras and VTRs.