It’s larger. As much as 6 times larger.
High definition video is certainly larger than standard definition video.
1080 format frame is 5.33 (perceived geometry) or 5.93 (resolving power) times larger than your old North American
720 format frame is 2.37 (perceived geometry) or 2.63 (resolving power) times larger than SD.
Imagine 6 TVs stacked in two rows of three TVs. That’s roughly how much 1080 format is larger than SD [Fig. 1].
Fig. 1. HD and SD Frame Size Comparison
So many standards confusing you? There are only three in use in the
For each standard you always wanted to ask about there are probably three others you have never heard of.
HDTVis not entirely new. There was a working system in Japan back in the late seventies. The analog standard was prohibitively expensive to consumers and it did not catch on in spite of outstanding image quality.
In 1996 President Clinton signed the Telecommunications Act of 1996 into law. This law created room for Advanced Television Standards Committee (ATSC) to create a new digital standard governing TV broadcasting in the U.S.
ATSC proposed a myriad of standards. There are only three HD standards that are worth considering at this time:
standard pixel dimensions frames-per-second
1080 23.98p 1920×1080 23.98
1080 59.94i 1920×1080 29.97
720 59.94p 1280×720 59.94
These three standards have been currently accepted by major equipment manufacturers. There is a fourth format rapidly gaining inroads in video cameras but at the moment no VTR supports 720 23.98p recording.
U.S. broadcasters have adopted only 1080 59.94i and 720 59.94p. This means that whatever you shoot will be broadcast in one of these formats. 1080 23.98p is solely an acquisition and post production mastering format at this time. The benefits of 1080 23.98p are discussed in more detail here.
There are also standards proposed by European Broadcasting Union (EBU) such as 1080 25p.
Which standard to choose for your production? Find out here.
Pick a number.
| Name | Pixel Dimensions | Interlaced fps | Progressive fps |
| 720 | 1280×720 | n/a | 23.976p, 24p, 25p, 29.97p, 30p, 59.94p, 60p |
| 1080 | 1920×1080 | 50i, 59.94i, 60i | 23.976p, 24p, 25p, 29.97p, 30p |
Note: 23.976p is commonly rounded to 23.98p for clarity. “Interlaced fps” is commonly expressed in fields. 50i is really 25fps. Not all the above frame rates are supported by equipment manufacturers.
A professional grade digital HD interface.
HD SDI stands for High Definition Serial Digital Interface. This type of connection is found on higher end VTRs, monitors, NLE capture cards and other equipment.
It is capable of carrying uncompressed HD video. Depending on the implementation it may also carry several embedded audio tracks and ancillary information.
Digital Television.
DTV is a set of digital television standards set forth by ATSC and bound to replace NTSC in the
DTV has certain advantages over NTSC. It uses less bandwidth per channel than NTSC requiring a narrower spectrum of radio frequencies. It allows for multichannel sound, electronic program guides, interactivity and other amenities.
In practical implementation DTV is compressed using lossy MPEG-2 codec sometimes resulting in picture artifacts.
HDTV is a subset of DTV standards. DTV is not necessarily in high definition but it defines a number of HD standards proposed for use in the
Synchronizing signal for SD equipment.
Black burst is the signal which provides heartbeat to standard definition equipment. The purpose of the signal is to synchronize various pieces of video and audio gear so they may work in concert with each other.
Black burst is a PAL or NTSC signal containing black picture. The actual picture content is of no consequence but black is typically used as means of providing neutral content. It is generated by a sync generator and distributed to various pieces of equipment throughout the facility.
In certain situations it is possible to use the black burst in place of tri-level sync for HD applications.
1.78 for HD, 1.33 for SD.
Aspect ratio is the quotient of screen’s width and screen’s height. For example, a standard definition frame is 4 units wide and 3 units tall which is 4:3=1.33. Aspect ratio for SD is commonly expressed as either 1.33, 4×3 or 4:3.
The HD screen is wider. It is 16 units wide and 9 units tall which is: 16:9=1.78. You will see any of these: 1.78, 16×9 or 16:9. Sometimes you may run into 1.77 which is practically the same as 1.78.
The difference in aspect ratios between HD and SD requires you to specify the target aspect ratio when creating SD downconversions.
Fig.1. High Definition and Standard Definition Aspect Ratios
You hardly need to concern yourself with Progressive Segmented Frame.
You may have seen master tapes from post production facilities labeled with 1080 23.98PsF or 1080PsF instead of “23.98p.” For practical purposes this designation does not change a thing. If a network requires a 23.98p delivery (they may erroneously call it “24p”) what they really mean is a 23.98PsF tape.
Progressive segmented frame was developed to be compatible with legacy video electronics which are not designed for use with progressive signal. PsF also reduces apparent flicker at 23.98fps which is a low frame rate.
More the better.
A simple rule of thumb: when you add up the three numbers the highest sum has the best quality — most of the time.
The three digit ratio specifies the digital sampling structure of HD as well as SD video. Without getting into technical details, VTRs that use 4:4:4 provide the best possible color recording, 4:2:2 is the next one down, 3:1:1 and so forth.
The differences between various sampling structures are invisible to most casual viewers but may come into play in post production when the material is subjected to color correction, keying and compositing.
The ratio does not only apply to VTRs but to any digital device or software that processes video in Y’CrCb (component digital) domain.
Some popular HD VTR formats and their sampling ratios (note that the sampling ratio is not the only factor determining quality of a format):
HDCAM SR 4:4:4
D5 4:2:2
DVCPRO HD 4:2:2
HDCAM 3:1:1
XDCAM 4:2:0
HDV 4:2:0
High end camera systems capable of 24 fps.
Varicam is a high end DVCPRO HD camera system by Panasonic which allows you to capture variable frame rates on HD video. Other manufacturers have adopted similar systems although they do not share the Varicam designation.
There are also lower end camera models by Panasonic that have similar variable frame rate capability although Varicam label is omitted.
Varicam frame rate is selectable in the frame range of 4 to 60 frames per second (fps). Overcranking and undercranking effects can be achieved in camera and some post production processing.
The frame rate of 24 fps or more properly 23.98 fps is of most interest to producers. It closely resembles the speed and temporal quality of motion picture film.
The camera shoots 59.94 fps at any time. It achieves the look of 23.98p by using a process called 3:2 pulldown.
The math behind the process is simple. Each frame is frozen for a period of two frames with the next frame frozen for a period of three frames creating a freeze sequence that looks like this: 3:2:3:2:3:2… Over a period of 60 frames there is a perceived count of 24 discreet frames and the illusion of 24 fps is sustained.
Post production editing of this format is a bit more complex than “true” 23.98p formats. It is a good idea to discuss the offline/online workflow with an experienced editor or post supervisor first.