08-17-2022-0452 - 7267/8-9,10-11
Wednesday, August 17, 2022
08-17-2022-0300 - transmission level point (TLP)
In telecommunication, a transmission level point (TLP) is a physical test point in an electronic circuit, typically a transmission channel, where a test signal may be inserted or measured.[1] Typically, various parameters, such as the power of the signal, noise, or test tones inserted are specified or measured at the TLP.
The nominal transmission level at a TLP is a function of system design and is an expression of the design gain or attenuation (loss).
Voice-channel transmission levels at test points are measured in decibel-milliwatts (dBm) at a frequency of ca. 1000 hertz. The dBm is an absolute level with respect to 1 mW. The TLP is thus characterized by the relation:[1]
- TLP = dBm — dBm0
When the nominal signal power is 0 dBm at the TLP, the test point is called a zero transmission level point, or zero-dBm TLP. In general, the term TLP is commonly used as if it were a unit, preceded by the nominal level for the test point. For example, the expression 0 TLP refers to a 0 dBm TLP. At a −16 TLP, the measured level of 0 dBm is +16 dBm0.
The level at a TLP where an end instrument, such as a telephone set, is connected is usually specified as 0 dBm.
References[edit]
https://en.wikipedia.org/wiki/Transmission_level_point
08-17-2022-0258 - full scale
In electronics and signal processing, full scale represents the maximum amplitude a system can represent.
In digital systems, a signal is said to be at digital full scale when its magnitude has reached the maximum representable value. Once a signal has reached digital full scale, all headroom has been utilized, and any further increase in amplitude will result in an error known as clipping. The amplitude of a digital signal can be represented in percent, full scale, or decibels, full scale (dBFS).
In analog systems, full scale may be defined by the maximum voltage available, or the maximum deflection (full scale deflection or FSD) or indication of an analog instrument such as a moving coil meter or galvanometer.
Processing[edit]
The signal passes through an anti-aliasing, resampling, or reconstruction filter, which may increase peak amplitude slightly due to ringing.
It is possible for the analog signal represented by the digital data to exceed digital full scale even if the digital data does not, and vice versa. Converting to the analog domain, there is no clipping problem as long as the D/A analog circuitry is well designed. In the digital domain, there are no peaks created by these conversions.
If a full-scale analog signal is converted to digital via A/D with sufficient samples, and then reconverted to analog via D/A, the Nyquist theorem guarantees that there will be no problem in the analog domain due to "peak" issues because the restored analog signal will be an exact copy of the original analog signal. (However, if the signal is normalized in the digital domain, it may contain "intersample peaks" which exceed full scale after analog reconstruction.)[5]
https://en.wikipedia.org/wiki/Full_scale
08-17-2022-0257 - Audio normalization
Audio normalization is the application of a constant amount of gain to an audio recording to bring the amplitude to a target level (the norm). Because the same amount of gain is applied across the entire recording, the signal-to-noise ratio and relative dynamics are unchanged. Normalization is one of the functions commonly provided by a digital audio workstation.
Two principal types of audio normalization exist. Peak normalization adjusts the recording based on the highest signal level present in the recording. Loudness normalization adjusts the recording based on perceived loudness.
Normalization differs from dynamic range compression, which applies varying levels of gain over a recording to fit the level within a minimum and maximum range. Normalization adjusts the gain by a constant value across the entire recording.
https://en.wikipedia.org/wiki/Audio_normalization
The loudness war (or loudness race) is a trend of increasing audio levels in recorded music, which reduces audio fidelity and—according to many critics—listener enjoyment. Increasing loudness was first reported as early as the 1940s, with respect to mastering practices for 7-inch singles.[1] The maximum peak level of analog recordings such as these is limited by varying specifications of electronic equipment along the chain from source to listener, including vinyl and Compact Cassette players. The issue garnered renewed attention starting in the 1990s with the introduction of digital signal processing capable of producing further loudness increases.
With the advent of the compact disc (CD), music is encoded to a digital format with a clearly defined maximum peak amplitude. Once the maximum amplitude of a CD is reached, loudness can be increased still further through signal processing techniques such as dynamic range compression and equalization. Engineers can apply an increasingly high ratio of compression to a recording until it more frequently peaks at the maximum amplitude. In extreme cases, efforts to increase loudness can result in clipping and other audible distortion.[2] Modern recordings that use extreme dynamic range compression and other measures to increase loudness therefore can sacrifice sound quality to loudness. The competitive escalation of loudness has led music fans and members of the musical press to refer to the affected albums as "victims of the loudness war".
History[edit]
The practice of focusing on loudness in audio mastering can be traced back to the introduction of the compact disc,[3] but also existed to some extent when the vinyl phonograph record was the primary released recording medium and when 7-inch singles were played on jukeboxmachines in clubs and bars. The so-called wall of sound (not to be confused with the Phil Spector Wall of Sound) formula preceded the loudness war, but achieved its goal using a variety of techniques, such as instrument doubling and reverberation, as well as compression.[4]
Jukeboxes became popular in the 1940s and were often set to a predetermined level by the owner, so any record that was mastered louder than the others would stand out. Similarly, starting in the 1950s, producers would request louder 7-inch singles so that songs would stand out when auditioned by program directors for radio stations.[1] In particular, many Motown records pushed the limits of how loud records could be made; according to one of their engineers, they were "notorious for cutting some of the hottest 45s in the industry."[5] In the 1960s and 1970s, compilation albums of hits by multiple different artists became popular, and if artists and producers found their song was quieter than others on the compilation, they would insist that their song be remastered to be competitive.
Radio broadcasting[edit]
When music is broadcast over radio, the station applies its own signal processing, further reducing the dynamic range of the material to closely match levels of absolute amplitude, regardless of the original recording's loudness.[38]
Competition for listeners between radio stations has contributed to a loudness war in radio broadcasting.[39] Loudness jumps between television broadcast channels and between programmes within the same channel, and between programs and intervening adverts are a frequent source of audience complaints.[40] The European Broadcasting Union has addressed this issue in the EBU PLOUD Group with publication of the EBU R 128 recommendation. In the U.S., legislators passed the CALM act, which led to enforcement of the formerly voluntary ATSC A/85 standard for loudness management.
https://en.wikipedia.org/wiki/Loudness_war
See also[edit]
Notes[edit]
- ^ Up to 2 or 4 consecutive full-scale samples was considered acceptable.
- ^ Usually in the range of −3 dB.
- ^ Look-ahead is a window of time in which the processor analyzes the audio amplitude in advance and predicts the amount of gain reduction needed to meet the requested output level (0 dBFS); this permits the limiter to react to incoming transients avoiding clipping. Since an audio buffer is needed to achieve this, look-ahead is only possible in the digital domain and introduces a small amount of latency to the output signal.
- ^ The vinyl version of this album does not have the same quality issues.
- ^ Won Grammy Award in 2006 for Best Engineered Album, Non-Classical
- ^ The 2015 remaster of this compilation does not have the same quality issues.
- ^ The Guitar Hero version of this album does not have the same quality issues.
- Van Buskirk, Eliot (16 September 2008). "Analysis: Metallica's Death Magnetic Sounds Better in Guitar Hero". Wired. Retrieved 17 September 2008.
- ^ Michaels, Sean (1 October 2008). "Death Magnetic 'loudness war' rages on". The Guardian. London. Retrieved 17 October 2008.
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08-17-2022-0257 - alignment level
The alignment level in an audio signal chain or on an audio recording is a defined anchor point that represents a reasonable or typical level. It does not represent a particular sound level or signal level or digital representation, but it can be defined as corresponding to particular levels in each of these domains.
Digital audio players such as the iPod, demonstrate the need for a common alignment level. While tracks taken from recent CDs sound loud enough, many older recordings (such as Pink Floyd albums which notably allowed much headroom for stunning dynamic range and rarely reach peak digital level) are far too quiet, even at full volume setting. Older audio systems typically incorporated 12dB of 'overvolume', meaning that it was possible to turn up the loudness on a quiet recording to make maximum use of amplifier output even if peak level was never reached on the recording. Modern devices, however, tend to produce maximum output at full volume only on recordings that reach full-scale digital level. If extra gain is added, then playing a modern CD after listening to a well-recorded older one is likely to deafen, requiring the volume control to be turned down by a huge amount. Again, the adoption of a common alignment level (early CDs allowed around 18dB of headroom by common consent) would make sense, improving quality and usability and ending the loudness war.
https://en.wikipedia.org/wiki/Alignment_level
08-17-2022-0256 - normalization (image processing)
In image processing, normalization is a process that changes the range of pixel intensity values. Applications include photographs with poor contrast due to glare, for example. Normalization is sometimes called contrast stretching or histogram stretching. In more general fields of data processing, such as digital signal processing, it is referred to as dynamic range expansion.[1]
The purpose of dynamic range expansion in the various applications is usually to bring the image, or other type of signal, into a range that is more familiar or normal to the senses, hence the term normalization. Often, the motivation is to achieve consistency in dynamic range for a set of data, signals, or images to avoid mental distraction or fatigue. For example, a newspaper will strive to make all of the images in an issue share a similar range of grayscale.
Normalization transforms an n-dimensional grayscale image with intensity values in the range , into a new image with intensity values in the range .
The linear normalization of a grayscale digital image is performed according to the formula
For example, if the intensity range of the image is 50 to 180 and the desired range is 0 to 255 the process entails subtracting 50 from each of pixel intensity, making the range 0 to 130. Then each pixel intensity is multiplied by 255/130, making the range 0 to 255.
Normalization might also be non linear, this happens when there isn't a linear relationship between and . An example of non-linear normalization is when the normalization follows a sigmoid function, in that case, the normalized image is computed according to the formula
Where defines the width of the input intensity range, and defines the intensity around which the range is centered.[2]
Auto-normalization in image processing software typically normalizes to the full dynamic range of the number system specified in the image file format.
https://en.wikipedia.org/wiki/Normalization_(image_processing)
08-17-2022-0254 - Grey
Grey (more common in British English) or gray (more common in American English) is an intermediate color between blackand white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be composed of black and white.[2] It is the color of a cloud-covered sky, of ash and of lead.[3]
The first recorded use of grey as a color name in the English language was in 700 CE.[4] Grey is the dominant spelling in European and Commonwealth English. Gray has been the preferred spelling in American English.
In Europe and North America, surveys show that grey is the color most commonly associated with neutrality, conformity, boredom, uncertainty, old age, indifference, and modesty. Only one percent of respondents chose it as their favorite color.[5]
Optics[edit]
Over the centuries, artists have traditionally created grey by mixing black and white in various proportions. They added a little red to make a warmer grey, or a little blue for a cooler grey. Artists could also make a grey by mixing two complementary colors, such as orange and blue.
Today the grey on televisions, computer displays, and telephones is usually created using the RGB color model. Red, green, and blue light combined at full intensity on the black screen makes white; by lowering the intensity, it is possible to create shades of grey.
In printing, grey is usually obtained with the CMYK color model, using cyan, magenta, yellow, and black. Grey is produced either by using black and white, or by combining equal amounts of cyan, magenta, and yellow. Most greys have a cool or warm cast to them, as the human eye can detect even a minute amount of color saturation. Yellow, orange, and red create a "warm grey". Green, blue, and violet create a "cool grey".[14] When no color is added, the color is "neutral grey", "achromatic grey", or simply "grey". Images consisting wholly of black, white and greys are called monochrome, black-and-white, or greyscale.
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| Warm grey | Cool grey |
| Mixed with 6% yellow. | Mixed with 6% blue. |
- RGB model
- Grey values result when r = g = b, for the color (r, g, b)
- CMYK model
- Grey values are produced by c = m = y = 0, for the color (c, m, y, k). Lightness is adjusted by varying k. In theory, any mixture where c = m = y is neutral, but in practice such mixtures are often a muddy brown (see discussion on this topic).
- HSL and HSV model
- Achromatic greys have no hue, so the h code is marked as "undefined" using a dash: --; greys also result whenever s is 0 or undefined, as is the case when v is 0 or l is 0 or 1
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| Grey/Gray | |
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 Color coordinates | |
| Hex triplet | #808080 |
| sRGBB (r, g, b) | (128, 128, 128) |
| CMYKH (c, m, y, k) | (0, 0, 0, 50) |
| HSV (h, s, v) | (0°, 0%, 50%) |
| CIELChuv (L, C, h) | (54, 0, 0°) |
| Source | HTML/CSS[1] |
| B: Normalized to [0–255] (byte) H: Normalized to [0–100] (hundred) | |
https://en.wikipedia.org/wiki/Grey
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