High-definition Television - Notation

Notation

HDTV broadcast systems are identified with three major parameters:

• Frame size in pixels is defined as number of horizontal pixels × number of vertical pixels, for example 1280 × 720 or 1920 × 1080. Often the number of horizontal pixels is implied from context and is omitted, as in the case of 720p and 1080p.
• Scanning system is identified with the letter p for progressive scanning or i for interlaced scanning.
• Frame rate is identified as number of video frames per second. For interlaced systems an alternative form of specifying number of fields per second is often used.

If all three parameters are used, they are specified in the following form: or /. Often, frame size or frame rate can be dropped if its value is implied from context. In this case the remaining numeric parameter is specified first, followed by the scanning system.

For example, 1920×1080p25 identifies progressive scanning format with 25 frames per second, each frame being 1,920 pixels wide and 1,080 pixels high. The 1080i25 or 1080i50 notation identifies interlaced scanning format with 25 frames (50 fields) per second, each frame being 1,920 pixels wide and 1,080 pixels high. The 1080i30 or 1080i60 notation identifies interlaced scanning format with 30 frames (60 fields) per second, each frame being 1,920 pixels wide and 1,080 pixels high. The 720p60 notation identifies progressive scanning format with 60 frames per second, each frame being 720 pixels high; 1,280 pixels horizontally are implied.

50 Hz systems support three scanning rates: 50i, 25p and 50p. 60 Hz systems support a much wider set of frame rates: 59.94i, 60i, 23.976p, 24p, 29.97p, 30p, 59.94p and 60p. In the days of standard definition television, the fractional rates were often rounded up to whole numbers, e.g. 23.976p was often called 24p, or 59.94i was often called 60i. 60 Hz high definition television supports both fractional and slightly different integer rates, therefore strict usage of notation is required to avoid ambiguity. Nevertheless, 29.97i/59.94i is almost universally called 60i, likewise 23.976p is called 24p.

For commercial naming of a product, the frame rate is often dropped and is implied from context (e.g., a 1080i television set). A frame rate can also be specified without a resolution. For example, 24p means 24 progressive scan frames per second, and 50i means 25 interlaced frames per second.

There is no standard for HDTV color support. Until recently the color of each pixel was regulated by three 8-bit color values, each representing the level of red, blue, and green which defined a pixel color. Together the 24 total bits defining color yielded just under 17 million possible pixel colors. Recently some manufacturers have produced systems that can employ 10 bits for each color (30 bits total) which provides for a palette of 1 billion colors, saying that this provides a much richer picture, but there is no agreed way to specify that a piece of equipment supports this feature. Human vision can only discern approximately 1 million colors so an expanded color palette is of questionable benefit to consumers.

Most HDTV systems support resolutions and frame rates defined either in the ATSC table 3, or in EBU specification. The most common are noted below.