Have any questions? +49 221 6778932-0 or sales@flexypage.de


Audio and Video

Everyone knows about MP3s by now, and almost everyone uses YouTube. Whereas in the past one had to wait for a song to be played on the radio, it is now possible to find the whole history of music only one click away. Be it by buying MP3s or using a streaming service. But what other files exist besides MP3s and how do they differ? And how are videos saved, given that they include sound as well as images?

Audio File Formats

Audio files can be saved in different formats on a storage medium. Uncompressed audio files take up a lot of space. Therefore audio information is often saved in a compressed format. The typical uncompressed format is PCM, which is saved as .wav under Windows and as .aiff under OS. These file formats contain the unedited original information. The compressed formats are divided into lossy and lossless formats. The lossless formats decrease the data by means of compression measures that allow for the restoration of the original data. Examples are MPEG-4 SLS, MPEG-4 ALS, Windows Media Audio Lossless (WMA Lossless) and Shorten (SHN). To create lossy formats the measures of compression will be accompanied with measures to reduce the amount of data. Tones that are not recognizable by human ears are deleted from the audio files. This way, it is possible to create even smaller files, while reducing the quality of the audio signal. In most cases, however, this is reasonable, for example, with telephony, where the transmission of the message is important and not the sound, or in environments where this a lot of ambient noise. Examples for lossy file formats are MP3, AAC, or Windows Media Audio Lossy (WMA Lossy).

Video File Formats

Recording video data creates data volume that is a lot higher than the volume of audio data. Effective compression measures are even more important here, to make the data easier to save and to transmit. Achievable rates of compression are between 1:5 and 1:200.

Among the common video file formats are WMV (Windows Media Video), MPG (Moving Pictures Experts Group I und II) and MP4 (Moving Pictures Experts Group 4), AVI (Audio Video Interleaved), FLV (Flash Video), MOV (Apple Quicktime Movie) or RM (Real Media). These file formats are usually proprietary container formats, in which the data is saved by using several different codecs or the same codec.

video compression

Audio Codecs

An Audio-Codec is a device or computer program that codes and decodes a digital data stream in bits to save audio-information. Most codecs contain both an ADC (Audio-to-Digital Converter), as well as a DAC (Digital-to-Audio Converter). They also contain measures to reduce data size.

Video Codecs

A video codec is a program or device that codes and decodes video information. To code and decode the same codec has to be used. A popular video codec is H.264, whose efficiency is up to three times that of his predecessor MPEG-2 (H.262) and which is able to compress videos in HD. As a result of this efficient compression the space is reduced, but the computing power has to increase accordingly.