Digital Media: Formats, Compression, and Processing

Posted on May 16, 2024 in Computers

Image Format and Compression

Lossless Compression

Huffman-Encoding: Performing a frequency table.

-RLE (Run Length Encode): Replaces sets of repeated values for a key with a numeric indicator (3 * 2).

-LZW (Lempel-Ziv-Welch): When you find a similar sequence to another, it is replaced by a code of two values, corresponding to how many steps are reversed and how much data is repeated (101 # 32). It is used in GIF or TIFF.

Lossy Compression

.- Method fractal: Divided into blocks, scaling, rotation, we can reconstruct the image at different scales. “JPG”

Psycho-visual Redundancy: It eliminates what the human eye cannot identify.

Vector Media Types:

Graphic based composed of curves and lines.

  • TIFF: High quality, but hard to see where we store too much information.
  • Raw: RAW file without any compression.
  • PSD: Photoshop file.
  • JPG: Lowest to highest quality compression.
  • GIF: Animations through sequential frames.
  • PNG: Equal to GIF, but does not allow animated files.

Audio Capture and Compression

Sampling

Is it possible to accurately repeat a waveform if the sampling rate is at least twice the frequency of the higher frequency component? There are 3 forms of compression:

Isophane Curves: Low-intensity differences in the curves are more pronounced; for high intensities, the curves are flattened.

Temporal Masking: If two stimuli of different intensity sound reach our ears so close in time, the more intense tone can mask the weak, so as to be inaudible.

Simultaneous Masking: When the ear is exposed simultaneously to two or more sounds of different frequencies, it is possible that one of them is masked by the other, resulting in being inaudible.

Media Types

  • MP3: Good compression (up to 2 channel stereo)
  • OGG: Record polyphony
  • MIDI: Musical Instrument Digital Interface
  • WMA: Windows Media Player
  • WAV: Waveform audio file

Audio Quality

64kb/s – 128kb/s – 192 kb/s. The audio is processed in the following ways:

Flanger: This is a paper filter (comb-shaped) of a series of frequencies determined by the delay time.

Chorus: Used to “thicken” the signal, or to simulate the existence of several instruments playing.

Distortion: Transforms the input signal into a square wave. That causes the result to tend to be nasty and scraping.

Success: It generates even harmonics of the input signal; it can also be used to generate subharmonics to enhance serious tessitura instruments, or providing more body. Finally, it can be successfully used in the restoration of sound recordings from vinyl or defective.

Transpositor: Initially, mechanical transpositions were based on altering the playback speed of a tape on its speed at the time of recording.

Sound Filtering

The most commonly used device to transform the timbre of sound is the equalizer. An equalizer allows modifying the input signal so that certain components of its structure or leave its spectrum attenuated or amplified. An equalizer allows a maximum handle of 3 parameters:

Frequency of action or central: To determine which region of the spectrum you want to act on.

Bandwidth or Q factor: To determine the region around the central frequency (the closer, the more precise the change – but probably will be less clear -).

Level attenuation/amplification: To determine the magnitude in dB we need to enhance or reduce the band on which we act.

An equalizer can be:

Parametric: Whether to manipulate the three above parameters.

Semiparametric: If Q is predetermined and can only alter the other two parameters (common to many mixers).

Graphic: If it consists of a fixed number of frequencies (8, 15, 31) of action, with a fixed Q, so it just lets you change the level of attenuation/amplification (with 31 bands and a third octave Q can be the equalizer typically used to adjust tonally a room).

Compression and Video Processing

Video

Video refers to the gathering, processing, transmission, and electronic reconstruction of a sequence of sounds and images that represent scenes in motion. Etymologically, the word video comes from the Latin verb videre, meaning “I see.” The digital video system is handled through the computer. The information processed is a series of established values and understood by the computer, based on zeros and ones, known as BIT.

Differences Between Digital and Analog Video

  • In a digital video system, image quality is totally independent; it is affected only during the scanning process. In the analog system, it depends on the quality of the video cassette player, etc.
  • The digital system allows non-linear editing; we can edit the images and the sound more quickly without following any order. In changing the system of analog video editing, it follows the linear approach, as it depends on a magnetic tape media and leads to following an order in the filming sequence.
  • The colors in video editing are limited to analog when reproducing an image in contrast and brightness levels. In digital video, it uses three primary colors, making the colors of the image more accurately defined.
  • In the digital video system, making copies does not have any kind of loss in quality, being able to make as many copies as you want, whereas in the analog system, quality depends on the number of copies and recordings as well as other external components.

The different uses that you can give to a movie are: File Storage, Streaming, player lounge.

Compression Methods

The intra-frame or spatial compression: Compresses each frame separately. The intra-frame images are complete. This method is of higher quality, making it occupy more space, such as AVI.

– The inter-frame: Is one method that compresses from similarities between frames. This method is of low quality.

Formats

  • MPG, MPEG (Moving Picture Experts Group)
  • AVI and AVI2: AVI (Audio Video Interleave)
  • Microsoft Windows Media Video: The extensions of this type of content are: .asf and .wmv
  • Real Video: RM, RMVB (RM compression format that allows you to define how many bits per second and how much is dedicated to audio to video)
  • Apple QuickTime: files .mov
  • DV: Digital video, digital cameras

Codec

A codec is neither more nor less than a series of algorithmic functions necessary to compress a file; this compression process is called “coding” and decompressing or decoding the audio and video data.

  • For AVI, MPEG, and DVD = DivX or XviD
  • To MPG = VCD CVCD

TV Standards

Analog

  • NTSC: (National Commission for Television Systems) is a coding system for color television transmission analog.
  • PAL: Phase Alternating Line (in Spanish Phase Alternate Line), is the name that designates the system encoding used in the transmission of analog television signals in most parts of the world.
  • SECAM: Séquentiel Couleur à Mémoire (French “Sequential color with memory), uses the same resolution as the PAL (625 lines), but transmits the color information sequentially in a Red and Yellow and Blue and Yellow line on the next.

Digital

  • ISDB (Integrated Services Digital Broadcasting) (Japan): Or integrated services digital transmission is the standard digital television and digital radio that Japan has created to allow radio and television stations to convert to digital. The ISDB data is distributed by: The ISDB-T (digital terrestrial television), ISDB-S (digital satellite television), ISDB-C (digital cable), and 2.6GHz band for wireless transmission.
  • DVB: Digital Video Broadcasting (DVB) (Europe): Is an organization that promotes internationally accepted standards for digital television, including HDTV and satellite television and data communications via satellite (one-way, called sDVB-IP, and bidirectional called DVB-RCS. The DVB distributed data: satellite (DVB-S and DVB-S2), cable (DVB-C and DVB-C2), Terrestrial television (DVB-T), terrestrial TV for handheld devices (DVB-H).
  • ATSC: Advanced Television System Committee (American): Is a group that is responsible for developing standards for digital television in the United States, six times the size of the previous resolution standards. However, it also includes a provider of images of different sizes, so up to six virtual channels of standard-resolution TV can be emitted by a single television channel 6 MHz bandwidth.

Interactive Tools

Intentional process of a group to achieve specific objectives, most software tools designed to support and facilitate the work. The main collaborative tools include: forums and mailing lists can be used as another form of collaborative work, sharing experiences, resources. Those that are in fashion are mainly blogs and wikis, Plone, Weblogs, MediaWiki, Drupal, Moodle, SharePoint, Portal, e-learning.

A log is not collaborative when you open a process of participation, as is a long monologue to address a specialist, not letting the comments, when not interacting with other teachers or students, in short: when it gives no educational performance.

Requirements to be collaborative:

  • Technical resources: sufficient computers in the center (and accessible) and also in homes (one of the keys is the continuation of education at home)
  • Human quality: commitment and involvement by working together
  • Rules clear and well defined to use
  • Lots of patience: it requires technical training and human learning

Collaborative software can be divided into three categories: collaboration, communication tools, conferencing tools, and collaborative management tools or groups.

Electronic Communication Tools

send messages, files, data or documents between people and facilitate the sharing of information (asynchronous collaboration), such as: Email, Voice mail, Web publishing.
Conferencing tools that facilitate the sharing of information, interactive (synchronous collaboration), eg, Data conferencing, voice conferencing
Video conferencing, chat rooms. Collaborative management tools that facilitate group activities, eg. Electronic calendars, project management systems, control systems, flow of business, knowledge management systems