Video quality measurement

You have to follow a set of rules and standards to be within the standard. Video levels are maximum and minimum values ​​that must be cared for not being out of range.

Carlos Noguera *

Our everyday life is based on references, they need to know if we are doing things right, to know at what time of day we are or where we are. We measure time in hours, distance and height in meters or feet depending on where we are, the speed in kilometers per hour or miles per hour just depending on the geographical location in which we find ourselves.

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We also measured by age, weight, height and compared with reference tables. The money we have is also based on a reference which is the currency of the country.

The architect when designing should set parameters and actual measurements then the manufacturer must follow as a reference. The packaging designer must create your boxes went really being assembled to fit well. Therefore, I repeat, our daily life is based on references.

Those who work in video and audio, whether on television, post houses, radio, recording studios, etc., not escampamos us to this reality. We also need to follow patterns, tables and references so that our work is well done.

Who makes the rules and parameters of conformity?
In the middle broadcast under certain parameters and rules that are set by regulators depending on the category follow. In the case of video and audio established standards, among others, by SMPTE (Society of Motion Picture & Television Engineers), EBU (European Broadcasting Union), ARIB (Japanese Association of Radio Industry and Businesses), NTSC (National Television continue System Committee) in the case of analog color TV in the United States and most countries in Latin America.

In the case of transmission, the rules are imposed by the regulator of radio frequency space of each country, in the case of the United States to use an example, governs the FCC (Federal Communications Commission). Who does not follow the broadcast via RF parameters can be fined or closed. These regulators follow the parameters established in the present case of digital television ATSC, DVB, ISDB-T, among others.

Parameters to follow on TV
In the case that concerns us, the rules usually followed in Latin America are those of SMPTE, NTSC, ATSC, DVB ISDB-t i.

In the years 40, 50 and until the mid-70 a pattern of adjustment known as Indian-head test pattern (Fig. 1) which was used for camera settings (which could last many hours), monitors used in the TV studios and at home. And Oscilloscopes settings of these cameras were used.

With the advent of color television for the years 1960 the pattern known as Color Bar SMPTE, consisting in its upper two thirds of 7 vertical bars to 75% of its current value was invented and are generated by the 7 possible combinations of the basic colors Red, Green and Blue (or its acronym in English RGB)

For the measurement of levels two basic instruments called WFM (Waveform Monitor) and Vectorscope (Fig.2) were used. The first is basically used to measure the intensity levels of luminance and the second chroma level.


In his time he was known to this pattern as Barra and Tone, as it was necessary to record bars and tone 1Khz then calibrate tape players and when a material is sent via microwave.

With the advent of the digital age, many changes have occurred in the world of measurement and quality control and although many still use color patterns and forms of measurement, the format has been changed to level values. They have also created new ways to measure because the video to be digitized now have "1" and "0", therefore, needed new tools that include analysis of the SDI signal and digital data.

Why is it necessary quality control?
As mentioned in the previous paragraphs, follow a set of rules and standards to be within the standard. Video levels are maximum and minimum values ​​that must be cared for not being out of range.

When we field production should care that natural light not to expose the image, and although the mechanical adjustment usually is done in the camera, the level is reviewed on an instrument.

In a multi-camera environment, we must ensure that all are calibrated equal (shading), otherwise we run the risk that the final material non-visually pleasing. Similarly synchronism between them and the rest of the production equipment.

When we have a signal to the air we must be constantly reviewing the levels, if we issue a saturated transmitter signal we can create clipping that can degenerate the transmitted signal.

In the case of digital video it is more critical because if we saturate a signal to digitize this, there is no turning back for that is that production with digital cameras have to be very careful even preventing degeneremos signal and instead of producing video are creating problems such as errors GAMUT. This degeneration can be generated not even a misuse of equipment if faulty installation, bad wiring, poor quality cables.

The art of making things right
Over time we have forgotten and only the quality care we have focused on content.

Being videographer, cameraman, producer, editor, highlighter, etc. It is to be an artist and although the artist is free to perform their art in the way that is best and more to your liking, within the audiovisual media must follow patterns. For this reason we must use tools and adequate and specific instruments that guide you and help you make optimal quality and work and the result of following the rules is to audiovisual art and do things right.

* Carlos Noguera is the sales manager for Latin America AudioVideo BrandBuilder, US-based company, the exclusive distributor for the United States and Latin America the company PHABRIX quality meters. You can contactale in the mail carlos @ avbbcorp.com

Quoting products and technical services for Latin America

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