Video Production and Broadcast Standards
It’s important to know the inner workings of the various standards for video resolution and frame rate in a little more detail than my video glossary goes into, so here is an explanation of the most common types you may come in contact with.
In the United States, the NTSC standard has been used since the 1950’s for video broadcasts. NTSC is also used in certain parts of Asia, while PAL and SECAM are standards used in Europe. Each standard carries its own specifications – and in fact there are several variations of each standard – but the video standard you will be using is going to be mainly determined by the country in which you live.
Frame rate describes the number of frames, or images, that are displayed per second of video. The human eye can detect jumps in anything below about 15 frames per second, but every video standard is well above this number. The NTSC standard frame rate, for instance, shows 29.97 frames every second.
It might seem odd that NTSC uses a fraction of a frame. This came about because the original television broadcasts in the 1950’s were at 30 frames per second in black and white. The fractional frame is missing because engineers found that when color was added to the signal the easiest way to incorporate the added
information into the signal was to slow it down very slightly. PAL and SECAM are both 25 frames per second, while film is shot at 24 fps.
Timecode measures video frames in realtime, and is set to Hours, Minutes, Seconds, and Frames. Since NTSC runs at fractions of a frame each second, it uses a type of timecode called drop-frame that adjusts itself every minute so that those 29.97 frames match exactly to the actual amount of time that has passed. By contrast, non-drop-frame timecode does not make this adjustment, so as time goes by the timecode becomes further and further offset from the actual amount of time that has passed.
Great strides have been made in the realm of resolution, and broadcast standards in the US have shifted to HD – High-Definition video. When you pop in a standard definition DVD and sit down to watch, you’re looking at video that is 720×480, or 720 pixels wide by 480 pixels high, which is a total of 345,600 pixels. High-definition video starts at the 720p standard and goes up from there. 720p is 1280×720, or 921,600 pixels of resolution. There is also 1080p and 1080i, which are each 1920×1080. So you can see that high-definition broadcast standards have significantly increased the ways in which we experience video.
The i and the p in these formats stand for interlaced and progressive. An interlaced video is one where each frame actually contains a split image of two separate frames. When the video is played back, the frames are deinterlaced and the two images are split so that they can be viewed separately again. This method is used to save bandwidth, while progressive scan imagery uses full-frame transmissions.
Aspect ratio is the measure of height in relation to width. A video’s resolution is measured in pixels, and its aspect ratio tells you the relationship between its vertical and horizontal pixels. The standard television aspect ratio is 4:3, meaning that for every four horizontal pixels, there are three vertical ones. Widescreen video used in widescreen televisions is 16:9, or sixteen horizontal pixels for every nine vertical ones.
There are a few other commonly used aspect ratios, for example those used in some films which are even wider than 16:9, the anamorphic formats 1.85:1 and 2.39:1. The term anamorphic refers to using a wide lens to record onto normal 35mm film, which is traditionally formatted to capture a standard 4:3 image. This is why when you watch an unedited widescreen film on a regular television you see black bars above and below the picture; these are the areas of the film’s frame where no image has been recorded due to the use of the anamorphic lens.
Resolution vs. Aspect Ratio
It’s important to understand the distinction between resolution and aspect ratio; resolution measures the total size of a video’s frame in pixels, whereas aspect ratio is a measurement of the relationship between its vertical and horizontal dimensions. Take the 4:3 aspect ratio, for example. You could have one video at 640×480 resolution and another at only 320×240. While the smaller 320×240 video has only 1/4 as many pixels of resolution as the larger one, they are nonetheless both still in the 4:3 aspect ratio.
Video Standards in Indie Filmmaking
Which of the various standards outlined above you use will be determined by where you live and what equipment you are using. Since most independent projects are done using video rather than film, you may have seen low budget movies that used a number of varying standards without even realizing it.
You can make a good film regardless of the video standards you are using, but knowing what you’re dealing with will help you to troubleshoot any situations that arise where you may be having a problem along the way. For any additional questions or concerns, feel free to contact me. I can’t always answer right away, but I will always try to respond.
Write a comment
You must be logged in to post a comment.