video
Video Specifications: Interlace - Frame Size - Frame Rate
INTERLACE
NTSC and PAL video images consist of two separate "interlaced" fields that together comprise a frame, while computer monitors display "progressive" images. This approach was introduced when TV was first invented due to a technical limitation. This legacy technique has been eliminated from newer video standards for High Definition television, which are "progressive" (images are drawn in one pass from top to bottom).
In the interlaced image, both interlaced groups of lines are known as a field, and are referred to as the upper field and the lower field.Video footage that includes high motion material that changes quickly, when displayed in a computer monitor will show a ghosted image superposed onto the actual image, In order to display crisp video on a computer monitor video frames must be "de-interlaced" by eliminating one of the fields.
FRAME SIZE
The standard line resolution for an NTSC television is 525 lines; for PAL it is 576 lines.For NTSC video images, the SMPTE 259M standard specifies that the 525 lines be represented as: 720 x 486 pixels. This default video size is commonly known as D1.Capturing footage from a DV source, however, yields a frame of 720 x 480 pixels. The difference between the D1 spec and the DV spec is only 6 vertical pixels, so by shaving off the 6 pixels from a D1 resolution, the DV format was able to have a native resolution with a multiple of 16 (480 / 16 = 30), which is used by many compression algorithms.
FRAME RATE
Video is essentially a sequence of frames displayed every second known as the frame rate, measured in frames per second (fps). In a broad sense, NTSC video runs at 30 fps, and PAL runs at 25 fps. In actuality NTSC runs at 29.97 fps.The odd frame rate is more of a mathematical issue than anything else — there are still 30 frames, but they run 0.1 percent slower than actual time, equivalent to a frame rate of 29.97 fps.
NTSC and PAL video images consist of two separate "interlaced" fields that together comprise a frame, while computer monitors display "progressive" images. This approach was introduced when TV was first invented due to a technical limitation. This legacy technique has been eliminated from newer video standards for High Definition television, which are "progressive" (images are drawn in one pass from top to bottom).
In the interlaced image, both interlaced groups of lines are known as a field, and are referred to as the upper field and the lower field.Video footage that includes high motion material that changes quickly, when displayed in a computer monitor will show a ghosted image superposed onto the actual image, In order to display crisp video on a computer monitor video frames must be "de-interlaced" by eliminating one of the fields.
FRAME SIZE
The standard line resolution for an NTSC television is 525 lines; for PAL it is 576 lines.For NTSC video images, the SMPTE 259M standard specifies that the 525 lines be represented as: 720 x 486 pixels. This default video size is commonly known as D1.Capturing footage from a DV source, however, yields a frame of 720 x 480 pixels. The difference between the D1 spec and the DV spec is only 6 vertical pixels, so by shaving off the 6 pixels from a D1 resolution, the DV format was able to have a native resolution with a multiple of 16 (480 / 16 = 30), which is used by many compression algorithms.
FRAME RATE
Video is essentially a sequence of frames displayed every second known as the frame rate, measured in frames per second (fps). In a broad sense, NTSC video runs at 30 fps, and PAL runs at 25 fps. In actuality NTSC runs at 29.97 fps.The odd frame rate is more of a mathematical issue than anything else — there are still 30 frames, but they run 0.1 percent slower than actual time, equivalent to a frame rate of 29.97 fps.