What is sound source compression?
In the old days, you used to put a CD-sized Walkman and a CD case with your favorite CDs in a bag and go out.
Today, you can carry a large number of songs in the palm of your hand and enjoy music anytime, anywhere. The evolution of the times is amazing. Why is it possible to do this? It’s all thanks to “audio compression”!
Why compress in the first place? Doesn’t the sound quality get worse?
Music data can generally be burned to CD (700MB) for only 80 minutes without compression, but when compressed, the data size is reduced to about 1/10, which is 10 times larger in a place with the same capacity. capable of recording music. In other words, up to 10 music CDs can be burned onto one CD. Also, you can attach emails and download them from the Internet thanks to “audio compression”!
The sound quality is annoying, but it is not 100% the same, but it can maintain the same sound quality as an audio CD.
“Audio compression” has become an indispensable part of our musical life. There are various audio compression methods like MP3 and AAC, but I think there are many people who say, “I really don’t understand the difference …”.
First of all, from the basics of music files.
Music files are roughly classified into three types: “uncompressed”, “lossy compression”, and “lossless compression”. The nature of each format is as follows.
■ Uncompressed The
Sound quality is good because it is not compressed, but the file size is large.
<File format: WAVE (WAV) / AIFF>
■ Lossy compression When
compresses with lossy compression, it cannot be undone and the sound quality deteriorates, but the file size can be reduced.
<File format: MP3 / WMA / Ogg Vorbis / AAC / AC3 / ATRAC3 / ATRAC3plus / RealAudio / TwinVQ>
■ Lossless compression
Even if it is compressed once, it can be restored to the original data, so there is no deterioration in sound quality. The file size will be a bit larger, but recently the capacity of the PC hard drive has also increased, which is why it is popular.
<File format: Flac / Monkey’s Audio / TTA / WMA Lossless / RealAudio Lossless / Apple Lossless>
What are the MP3s that you see often on the Internet?
It uses a lossy compression method that achieves a high compression rate and is an audio compression method that compresses the amount of data to approximately 1/11 (128 kbps) while maintaining the sound quality of a music CD. In other words, the voice is compressed cutting the data in the part that is difficult for humans to perceive. The original data is compressed with the idea that “this part cannot be heard accurately by the human ear, so cut it out!”
What is the AAC you hear often these days?
AAC is a relatively new audio compression method. ITunes uses it in familiar places. AAC has a compression efficiency 1.4 times higher than MP3 and the sound quality is almost the same. The name itself may not be heard as much as MP3, but it is actually used in many places. For example, QuickTime, BS digital / 110 degree, CS digital / digital terrestrial / single segment broadcast, “Chaku-Uta” mobile phone, and so on.
Various audio compression methods
In addition to MP3 and AAC, there are several methods of audio compression.
■ Uncompressed
WAVE
(WAV)
.wav WAV or WAVE (RIFF waveform audio format). A format for writing audio data developed by Microsoft and IBM. A file format used primarily by Windows.
AIFF .aif A file format for audio data developed by Apple Computer, the standard audio format for Mac. Mac version of WAVE.
■ Lossy compression
MP3 .mp3 The compression format that has been overwhelmingly popular until now. It uses a lossy compression method that achieves a high compression rate by reducing data that is difficult for humans to perceive. Downloading music from the Internet, etc.
WMA .wma Abbreviation for Windows Media Audio. It has a copyright protection function and is used for broadcast distribution. Like other major compression methods, it uses a lossy compression method that achieves a high compression rate by reducing data that is difficult for humans to perceive.
Ogg Vorbis .ogg Popular as a next generation format for MP3. It is a lossy audio compression standard similar to MP3, WMA, AAC, etc., but differs from existing standards in that it is a free and open standard. One of the main features is that there are fewer rights restrictions than other codecs and formats.
