Formats: what is digital sound Part 3
JointStereo, which is one of the features of MP3, means that instead of encoding stereo as two independent channels, it encodes calls. center channel and the difference from the original stereo channels.
Many audio components on stereo channels are the same, and encoding them on the common channel allows you to free up additional bandwidth for more detailed encoding of the difference, leading to improved quality.
Be sure to mention the variable bit rate or VBR. This means that the encoder changes the compression ratio on the fly, depending on the nature of the sound. This approach results in a smaller total file size or, if quality requirements increase, the same file size may produce better sound.
MP3 Pro
Introduced in 2001, the MP3 Pro codec was developed by Coding Technologies in association with Thomson Multimedia. It is MP3-based and as a result turned out to be fully MP3 backward compatible and only partially forward compatible. It uses SBR (Spectral Band Replication) technology, so the codec provides good quality at low bit rates. However, the encoding quality at medium to high bit rates is inferior to almost all other codecs. As a result, MP3 Pro is used more for streaming on the Internet and demonstrating snippets of new musical compositions.
WMA
The WMA codec, or Microsoft Windows Media Audio, is a serious alternative to MP3. Files in this format have the extensions .WMA and .ASF, have a clear advantage over MP3 at low data rates (bitrates) and lose it when the data feed rate to the codec is increased.
Based on WMA, the WMA DRM standard has been developed to provide copy protection so appreciated by record companies. Files based on this format can be recorded on playback devices such as MP3 flash players, but cannot be copied from there.
ATTRAC
ATRAC (Adaptive TRansform Acoustic Coding) is based on a stereo audio format with 16-bit quantization and a sample rate of 44.1 kHz. When compressed, each frame is divided into 52 frequency bands, resulting in a transmission rate of 292 kbps (1: 5 compression). Used in MiniDisk system.
Ogg Vorbis
The Ogg Vorbis format is a relatively new universal lossy audio recording format. It belongs to the same type of audio compression formats as MP3 and WMA, and the psychoacoustic model that describes the characteristics of the human ear, according to which compression is performed, is similar in principle to MP3. The radical difference of this format was the mathematical processing and the practical implementation of this model. In this format, the maximum threshold sample rate is not 44 kHz as in MP3, but 48, which theoretically improves the sound quality. It should also be noted that the theoretical number of channels is not limited to two, as usual, but reaches 255. Files encoded in this format are smaller than the same MP3 files. The spread of the format was slowed by insufficient support from hardware manufacturers.
