Image and Sound Formats: Types and Characteristics
Image Formats: Types and Characteristics
There are several types of image formats, each with its own characteristics and uses:
- Raster Images or Bitmaps: These are formed by many points (pixels) that, as a whole, define the final image. Each of these points has a specific color, luminosity, and contrast. The image files contain the information of the image in a dot matrix (pixels), so-called raster. When you save a bitmap image to a file, the characteristics of all points are stored.
- Vector Images: These images are created using lots of vectors or individual objects, each of which has its own definition (size, type of line, color, fill, etc.). The vector image files store the definition of all their components through mathematical expressions. This commonly makes this type of image smaller in size than the bitmap type.
- 3D Images: Such images may be created with different techniques, but their purpose is always to transmit the projection of something visual in a three-dimensional space. They are usually linked to animated pictures or animations.
- Animated Pictures (Animations): These are a first approximation to videos, since they allow transmitting a running sequence, but without sound.
Factors Affecting Image Quality
The quality of an image depends on several factors:
- Number of Pixels: The larger the number of points (pixels) used in the image, the better quality it has, since each point will be smaller and the image will be shown with more detail.
- Color Depth: This refers to the number of colors that the image has. The larger it is, the more shades it has.
- Compression of Information: When saving a bitmap image to a file, the information of each of its points or pixels is stored, consequently, the file size is very large. To avoid this, most graphical formats use some compression method, which implies a loss of quality to a greater or lesser extent.
Understanding Sound Waves
A sound wave is expressed as a sine function with the following parameters:
- Amplitude: This indicates the intensity of sound and is measured in decibels (dB). Noise levels above 85 dB can be dangerous; continuous exposure causes hearing damage.
- Wavelength: This is the separation between the crests of the wave and indicates the true distance that the sound travels over a time period.
- Frequency: This is the number of oscillations per second. The more frequency, the lower the wavelength. High frequencies are translated into high-pitched sounds and low frequencies into bass sounds. Frequency is measured in Hertz (Hz).
- Spectrum: This represents the intensity of sound for each one of the frequencies.
Digitalization of Sound
The digitalization of sound consists of the conversion of the analog wave into digital values that a computer system can interpret. To make this process, a microphone that converts wave sounds into electrical signals is used. Then, the sound card performs the analog/digital conversion. In order to listen to the digital sound, the inverse process has to be made, that is to say, the digital/analog conversion. This conversion is made by the sound card, amplifying the sound to the levels needed for vibrating the speaker cone that will again generate the sound waves which can be perceived by the human ear. The digitalization process takes place in three phases:
Phase 1: Sampling
Sampling consists of taking samples periodically from the original sound at regular intervals. The number of samples that are taken in about a second is called sampling frequency and is expressed in Hertz (Hz).
Phase 2: Quantification
Quantification consists of assigning to each sample a numeric value. The smaller the interval between the possible values, the more approximate the measurement will be.
Phase 3: Binary Coding
Audio Formats: Types and Characteristics
Uncompressed Formats
- MIDI (Musical Instrument Digital Interface): A communication protocol between the computer and other electronic music devices, being the most used in musical composition.
- CD-A or CDDA (Compact Disc Digital Audio): Uses as support the optical disc where the recording is carried out through a laser beam. It is a high-quality non-compressed format.
- WAV (Waveform Audio File): Microsoft’s format that is normally used in Windows for storing sound in different resolutions and sampling rates. It is not very popular on the Internet because the files are very large.
Lossless Compression Formats
- FLAC (Free Lossless Audio Codec): It is a free-license open format. It allows compressing an audio file up to half of the original size and decompressing it into a file identical to the original one.
- AIFF (Audio Interchange File Format): Developed by Apple, it can be distinguished by its fast signal processing.
Lossy Compression Formats
- MP3: One of the most popular formats due to its sound quality and small size.
- Ogg Vorbis: A free open format, based on the public GNU license. It can multiplex independent channels for audio, video, text, and metadata.
- WMA (Windows Media Audio): Audio compression technology.
- Real Audio: Widely used around the Internet because of its real-time playback without generating an audio file, for instance, on an online radio station. This format is often associated with the RealPlayer audio player.
- AAC (Advanced Audio Coding):