Video File Formats

MPEG's, AVI's and Web Formats

File Formats

AVI (Audio video interleave) files are native windows movie file formats. This is the un-compressed form. The first video files placed on the web were versions of AVI files. Depending on the specifications AVI files can be very small. Most are very large. Too large for the web. Too large for CD's. Various compressed formats were devised, such as MPEG's.

MPEG's (the name comes from Motion Picture Expert's Group) are among the most compressed of formats. DVD use various types of MPEG compression. The files extension is typically "mpg" after the filename.

But MPEG's are too large normally for easy web delivery. Apple's QuickTime was the first format designed with the internet in mind. RealMedia was next and then Windows Media. QuickTime, RealMedia and Windows Media all offer various bandwidth sizes. A number of methods are used to save movies in various bandwidths. The number of frames per second are reduced. The width and height of the frame size are reduced. Image-compression methods are applied within each of the images for each frame.

Video Tape Formats

The first practical video tape recorder was introduced in 1956 by Ampex after more than four years of work. Charles Ginzburg (left) was the project leader for that team. The videotape format was called Quadruplex. It used a 2-inch wide tape. Ampex also designed a video tape recorder for consumers in 1963 (VR 1500/600). A dizzying array of video formats were introduced in the years since 1956. Those first recorders were reel-to-reel recorders. Cassettes enclosed both reels into a single holder (the cassette shell). The life of those first recording heads was only 100 hours. The Ampex development team included Charles Ginsburg, Fred Pfost, Shelby Henderson, Ray Dolby, Alex Maxey, and Charles E. Anderson.

The first known video tape broadcast was November 30, 1956. CBS's Television City in Hollywood re-broadcast a delayed for the west coast news program, "Douglas Edwards and the News." By 1957 NBC and ABC were also using the Mark IV Ampex video recorder. This thing was the size of a desk. (Note: Ray Dolby was a 19-year old engineering student at the time who became part of the project, was drafted into the army and returned to the project after his service. He would later create Dolby sound technology found in recorders, players, movie theaters and more.)

Tape Formats
Format Name	Analog Digital	Resolution	Time	Description
The Analog Formats
VHS	Analog	250 lines	120 mins	Video Home System (1976)
VHS-C	Analog	250 lines	40 mins	The "C" stands for compact. The cassette is smaller than regular VHS but uses the same tape. It plays in regular VHS machines with a special adapter.
8mm	Analog	270 lines	120 mins	1983
Betacam Betacam Sp	Analog	300 lines 340 lines	varies	(1982) 1/2-inch tape in cassettes for pro use. Records component signals (separate red, green blue) for broadcast quality in analog format. Betacam SP (Superior Performance) in 1986 increased to 340 lines. Was TV-station standard into late 90's.
MII	Analog	340 lines	varies	1985 - as competitor to Betacam. Splits signal into red, green and blue (component signals).
S-VHS	Analog	400 lines	160 mins	The "S" stands for "Super" - These are easy to confuse with regular VHS tapes. They are the same size but need a special S-VHS machine to play. “S-video” separates the chrominance and luminance signals (color and brightness).
Hi-8	Analog	400 lines	120 mins	1989 - Notice that this small cassette has the same resolution as S-VHS. Prices on these are now (early 2004) running about $300. When Hi-8 cameras first came out in the early 90's they were commonly $2,000 to $2,500.
The digital formats
Digital-8 (D-8)	Digital	500 lines	60 mins	Uses the same size cassette as 8mm and Hi-8 and can playback both 8mm and Hi-8. For recording this format shares cassettes with Hi-8. This makes Digital-8 cameras backward compatible (if you own 8mm and Hi-8 tapes) and makes Digital-8 cameras a method for capturing 8mm and Hi-8 tapes directly to a computer or record to a digital tape on another camera. For persons who already have a lot of 8mm or Hi-8 tapes A Digital-8 camera is often a good move into digital at low cost. At this writing Digital-8's start at about $400.
DV	Digital	500 lines	60 mins	1996 - first digital available to consumers. Nearly loss-less picture.
MiniDV	Digital	500 lines	60 mins	See DV above.
Micro MV	Digital MPEG-2	530 lines	60 mins	obsolete: MPEG-2 data recorded on a very small cassette, no longer available
DVCAM	Digital	530 lines	varies	1996 - Includes a memory chip in cassette allowing logging (shot sheet) types of information to be recorded.
HDV	Digital	1080 lines	60 mins	Developed by JVC and Sony who were joined by Canon and Sharp to form the HDV consortium (2003). Usually stored only to tape but some cameras and digital recorders allow tapeless or tape+tapeless storage. HDV1 Aquires image at 1280x720 pixels HDV2 Aquires image at 1920x1080 pixels Creates "m2t" files during capture
XDCam	Digital	1080 lines	varies based on amount of storage capacity and on compression quality settings	2003 - Sony format for professional tapeless video on SxS (say: es and es) cards. In this it is similar to Panasonic's P2 cards except the SxS are designed for the newer, smaller PC-card form.
AVCHD	Digital	1080 lines	varies based on amount of storage capacity and on compression quality settings	(H.264 or MPEG-4 AVC) 2006 - stored to hard drive and/or memory card ( Audio and Video Compression for High Definition ) This was a consumer HDTV, Blu-Ray-compatible format developed from Sony's XDCAM professional tapeless format. Create files with "MTS" extension (stands for MPEG Transport Stream)

 

16 Years before the first video recorder

Click on the Play button to start Video
Early promotional film introducing TV to the American public, probably coordinated with the rollout of scheduled broadcasting at the 1939 New York World's Fair. Shows scenes of television production at the National Broadcasting Company (NBC) studios at Rockefeller Center, New York City, using equipment manufactured by NBC's corporate parent RCA. This start with a commercial for a 16-mm sound projector. This movie is part of the collection: Prelinger Archives Producer: Radio Corporation of America (RCA) Sponsor: Radio Corporation of America (RCA) Audio/Visual: Sd, B&W Keywords:
Creative Commons license: Public Domain

For our purposes (and budgets) Digital-8, Mini-DV, HDV and AVCHD are the most important. It is how we can reach pro-quality results on a beer budget. AVCHD (audio video codec high definition) is the latest popular format. Originall on consumer cameras it is now finding its way into pro-sumer cameras. The earlier versions of this format had motion and other artifacts (distortions in the image caused by the method used to make the image). Panasonic brought out the HMC-150 in October 2008 saving all video to the very small SDHC memory cards as AVCHD. This is widely considered the first pro/semi-pro use of the AVCHD format.

HDV is stored/recorded to the same miniDV tape used in standard def video cameras. Even though the shape of the video has a 16:9 ratio HDV manages to store the 33-percent wider format as a special case of the 4:3 ratio. Even when the camera records full 1920x1080 pixel images (16:9 ratio) it stores it on the tape as 1440x1080 (4:3 ratio). Then on editing and on play back this is expanded horizontally by one-third.

Video	Film
HiDef Video Camera HDV horizontal image compression from 16:9 to 4:3 and back 1 - Aquires image: compresses to 75-percent 2 - reconstitutes image: expands to 133-percent	Film Camera - such as a Panavision camera Anamorphic horizontal compression from 2:1 to 1:1 and back (Note: 2:1 is not the only width-to-height ratio, just a common one and easy to show as an example)

This is very similar to film camera's use of anamorphic lenses, such as on Panavision cameras starting in the 1950's when movies came up with the wide format to compete with the introduction of television which was using the long established 4:3 ratio screen. Panavision used and anamorphic lens to compress the picture horizontally on the film. The projector, then, had a corresponding anamorphic projection lens to spread the film image back to the original taking format on the screen.

The technical methods are different but the concept is the same. Each was a way to utilize existing equipment or technology for an expanded horizontal size, creating the wide screen.
1 - Film cameras were able to use the same film stock with the same 4:3 ratio apertures for the image on film.
2 - Video cameras were able to use the same miniDV tape used to store the older 4:3 ratio pictures.

Anamorphic lenses are not the only method used in film to get an image with a wider ratio. Changing the shape of the film gate for any given film size is one way, another way also increases the film size (i.e. going from 35mm to 70mm). In the end, the anamorphic-lens approach has remained for more than half a century now. Probably not so for HDV.

For video the 1920-to-1440-to-1920 pixel method is a bridge from standard def to hidef. But already the new crop of cameras are not only shooting native 1920x1080 but they are also storing it on either hard drive or removable solid-state media. That appears to be the new future, equivalent to the introduction of miniDV tape in the 90's.

Delivery of the full HD product is another matter. Blu-Ray appears to be too late for too much money and behind the curve for a distribution medium. Downloads (for commercial products) and direct play from memory cards is rapidly moving the market place. This would probably have been with us by 2000 had the telephone companies been willing to put in real broadband, as has the rest of the world.

Analog, Digital, Widescreen and HiDef

We need to clear up a certain amount of misunderstanding. These four words are used together, especially the last three, but their meanings are separate.

Analog- Type of Transmission and Type of Storage - strength of signal corresponds to intensity being recorded
Digital - Type of Transmission and Type of Storage - signal is a recording of measurements of what is being recorded
Widescreen - description of the picture format as much wider than the traditional 4:3 ratio
HiDef - Label for the amount of detail in a video picture - the resolution of the image

To get HiDef either analog or digital will work although all you see today is digital. HiDef equipment was up and working some years ago in analog.

Widescreen only describes the appearance of the rectangle containing the picture and has nothing to do with resolution (SD or HD) or with digital

Analog and Digital tell us both how the images are transmitted and how they are stored.

Analog stores information by varying the amount of signal (or the amount of frequency change - FM) according to the amount of what it is storing - the amount of color, the amount of brightness, the amount of volume and so forth. Changes in the strength of an analog signal or the frequency shift (FM) are analogous to whatever is being recorded.

Digital stores information as sampled measurements of the content. The more samples per second the more accurate the recording. Instead of changing the intensity or the frequency of the signal, digital stores the measurement of the signal's intensity. For example instead of sending a low-intensity signal (analog) for a low volume sound, the digital signal sends a low number representing that volume. When the volume is high digital sends a higher number. The number is a measurement called a sample.

Analog and Digital

An analog recorded wave form is a continuous recording of the sound. Varying intensities are recorded as varying intensities of magnetic field on the tape. Retaining the original quality depends on how well the signal retains its shape on the magnetic tape. Subtle changes occur over time. The tape signal tends to spread (or degrade) much like ink in a blotter pad.

A digitally recorded wave form is a sampling at a certain number of points in time. CD-quality for sound is 41,000 samples per second. Each "jaggie" in the picture above is a separate measurement (sample) which is recorded as a number. Even if the signal changes are subtle recording them as numbers is a format which is specific and whose value is non-degrading (unless you just can't read the number). This kind of recorded measurement can be read back reliably even from a badly degraded tape and reconstructed in its original form.

Neither analog nor digital formats are inherently superior in terms of output. Our senses don't pick up digital information. Our senses of hearing, sight, touch, taste and smell are all responses to analog events around us. Sound is analog. The visual spectrum sends us analog detail, intensity and color. Anytime we convert analog input to digital files we need to output the information in an analog format for us to see or hear. Yet convertions to and from digital formats have become essential to life in our world today. Digital formats are able to convey copies and copies of copies of sights and sounds in ways which do not lose quality with each generation.

Analog signals have varying amounts of intensity with an infinite number of possible states. Digital signals convey measurements of those varying intensities by using two states, on and off.

There are always two sides to the challenge of reproducing visual or aural information:

1. The degree of similarity to human senses that the manufactured sensors (such as mics and cameras) are able to capture the signals
2. The degree of closeness to the original scene that the output (such as speakers and photographs) are able to acheive so as to sound or look natural.

 

Here is the original analog signal. We see it below as recorded in two forms.

Above is a representation of magnetic field strengths in a length of tape. The strength of the magnetic field changes as the strength of the signal. This is variation in magnetic field is analogous to the original signal. The magnetic fields interact with each other and over time deteriorate to spread out the recording. This is similar to the way some inks wick into surrounding paper over time.

Above is a representation of a digital signal. It is not really a set of numbers in the form you see them but it is a set of digital patterns which record measurements of the signal strength. The digital patterns, even when deteriorated, can still provide accurate measurements just as long as the pattern can be discerned. This means that each time the measurements recorded as the digital signal is read an output is freshly constructed and looks like the original.

 

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Analog

First, an analog is a similar representation of some original. When we the world wide web runs on the internet superhighway we are making an analogy between highways our cars drive on and the transmission lines the internet uses to send electronic signals on.

An analog audio tape holds an "image" of the sound signal's varying amounts of strength in the way the recorder "writes" varying amounts of magnetic field strength on the tape. Where the sound has louder volume the tape has a stronger magnetic field and vice-versa. The signal can be strong enough that on thin tape it can cause "print through" problems. Print through happens when the magnetic field is strong enough on a part of the tape that it affects the layer of magnetic tape above or below causing a "ghosting" of the sound.

A film negative is an analog of the scene focused on it when the camera snapped the shutter. The emulsion is thicker in the areas where more light landed on it and thinner in areas which were darker. When the negative is enlarged to create a picture on paper the same thing happens again. Where more light from the negative lands on the paper (dark areas in the picture) more image is built up so that the darker areas are physically thicker portion of the paper's emulsion. When less light from the negative (the light areas in the picture) falls on the paper the image thickness is much thinner or not even there. You might think of photographic film and paper much like a very shallow geographic relief map.

You could even say that sound itself is an analogous representation of physical events which take place. Sound may represent the motion of a guitar string or the movement of a drum head. Just like the string or the drum head the sound comes in waves which mirror those starting movements. When these waves reach a microphone's diaphragm the diaphragm then moves in reaction to the air movements. This in turn produces a change in electric current. That is what we pick up, amplify and record.

There are always two types of challenges when recording analog data:

1. The degree of accuracy in representing the original signal
2. The ability to make copies with the smallest loss of quality compared to the original.

Digital

Digital signals are patterns which carry measurements of analog signals. All digital captures are measurements of sampled moments in time. The number of samples per second combined with the "bit-depth" in each measurement determine how accurate the eventual output.

Digital tape recordings are subject to the same kind of degradation as analog tape recordings but the effect on the information is very different.

In both digital and analog magnetic media the small metal or metal oxide particles which record the sound or video, etcetera, affect each other. Over time the tend to spread in much the same way that some ink, over time, may spread in a paper document.

The difference comes with what is stored. Digital storage is very impervious to loss because even when the signal is degraded it is not the shape of the signal but the pattern of the signal, ons or offs. The pattern is a number. Once you know the number that is all you need to reconstruct the original signal.

The Signal As Measurements

What really makes digital captures so powerful is the ability to manipulate them because they are stored as numbers. Analog signals can also be manipulated. Compressors and Expanders and Equalizers for example have been around a long time. They work by filtering and amplification or reduction of the analog signal.

Digital signals are not really signals in the same sense. They are long sets of numbers which are measurements. Because they are numbers they can be manipulated by computers in ways not previously available in analog equipment. Even though a lot of samples are taken per second of a sound wave, such as 41,000 or 48,000 or 96,000 samples per second, a typical computer runs so much faster that it can make changes in "real time."

While the sample is being taken in tens-of-thousandths of a second, the computer is running at 400 or 800 or more million operations per second. A computer running at 400 mhz is running almost 10,000 times faster than the sample rate of 41 khz. For that matter an old desktop computer from the late 80's or early 90's running at 40 mhz would be running at nearly 1,000 times the speed of a CD-quality capture.

A lot of evaluation and modification can be done in real time when you are running that much faster. When you don't need to worry about real time and are working with a saved sound file, even more can be done.

Playback and Hearing are Analog

Once the numbers are re-arranged the actual playback is done through an analog device. Remember, your senses are analog, not digital. The analog device, such as a speaker is not able to exactly reproduce each "jaggie" in the wave form. The mechanical constraints in its material, such as a paper cone to produce the sound, limit the range of frequencies it can handle accurately and as such help to smooth out the sound, "filling in" the spots between the sampled measurements.

In the last few years a number of specialized (and often premium price) sound equipment has been engineered with electronic tubes for what is seen as better sound quality. Ron Sutherland, a Kansas City engineer, is one of the top tube gurus and was one of the two creators of the most successful electrostatic speakers (manufactured in Lawrence). His "Sutherland" amplifiers and other equipment sell in the thousands of dollars and are reviewed in sound magazines across the world.

Although we are looking at a small part of a sound wave in on this page the same kind of digital manipulation and storage is also true of other digital media recordings such as video and still pictures. Measurements as numbers are made at certain locations in the information area. These numbers are stored and available for manipulation.

Morse Code Keyers

Morse Code and Digital Information

In the early 1800's a number of pioneers were trying to find a way to use electricity to transmit information. Eventually Samuel Morse's device won out. As a major method of transmitting information it would be king for most of the next 100 years. For another 60 years its usage would be less as voice methods became better.

Eventually digital computers would take over the job of delivering the bulk of the world's information. The data structure could be viewed as a variant on Morse Code. A digital signal has two states, on or off and so does Morse Code. The information is contained in the patterns of the ons and offs. The actual patterns are quite different between Morse Code and current digital data systems but the concept of two-state patterns for encoding information is much the same. There are no caps and smalls.

The two paragraphs below are taken from one of Alistaire Cooke's "Letters From America" series on BBC. This is a section about the game of golf.
Many more people than the suburban gentry took to tennis, just as the arrival in the mid '20s of Bobby Jones as the unbeatable one made everybody take up golf - from George Gershwin to the Emperor of Japan to Winston Churchill. Churchill took it up for about four rounds after which he snapped: "Golf! There's a game whose aim is to hit a small ball into an even smaller hole with weapons singularly ill-designed for the purpose."
Listen to a clear signal - Hear the two paragraphs above in Morse Code at a rate of 40 words-per-minute: Windows Media: 20kb	Listen with a "noise" obsuring the signal - Hear the same Morse Code file at the left but with noise added (sound and music loops). Notice how you can still pick out the "digital" signal - the pattern which holds the information. A filter designed to look just for the signal at the frequency of the tone will pull out the Morse while an analog system is foiled with all the extra sounds: Windows Media: 56kb, 128kb

 

Side Note : SOS (is not S O S)

Three dots followed by three dashes and then by three dots is the international distress signal. But surprise, although we call it "ess oh ess" it isn't really the three letters "S," "O" and "S." The pattern is called a procedural signal and unlike "S" "O" "S" there is no letter space between the two three-dot sections and the one three-dash section. (Three dots standing alone is an "S." Three dashes standing alone is an "O.") The SOS distress pattern is all run together to form its own complete signal (sort of a super-letter) which is termed a procedural signal.

Click here to listen to the SOS as a procedural signal at 20 words per minute (Windows Media). Notice how the entire nine element pattern (...---...) is keyed with a letter break after.

"SOS" doesn't stand for "save our ships" or "save our souls" or anything else. It was designed to be noticed with a minimum of energy expenditure. Up until the Titanic the letter combination "CQ" was used as a hail for attention (say "seek you"). It is like yelling out "Hello-o-O-O !!!!"
("CQ" is the name of the long-time HAM Radio magazine of the ARRL - American Radio Relay League.)

The letter combination of "CQD" (D=disaster) was proposed early on in the 1800's but wasn't adapted.

In the early 1900's the Germans proposed this pattern "...---." but thought the last dot might get lost or be confused.

The more distinctive "...---..." was recommended and adopted universally after the Titanic hit the iceberg in 1912. At that time the radio operator first used the older "CQ" and was then reminded about the newer "SOS" which he keyed into his transmitter. The attention from that tragedy really solidified the international distress code as "SOS."

Officially SOS has now been abandoned for shipping and international commerce because better electronic equipment linked to satellites make voice equipment and GIS distress transponders far more efficient. But in the absence of such emergency beacon equipment, being able to send out SOS with anything from flashlights, to hammers to patterns in snow and dirt still provides a universal and simple way to ask for help and to say there is someone here, someone alive.