Two ways to assign information: CBR and VBR
Recall that it is possible to have an approximate appreciation of the quality of an audio (or also video) file based on the amount of kilobits per second (kbps) with which that file is encoded – although, as stated in the previous post, Making comparisons considering this single parameter is not the best. We can define the measure of kbps as the amount of information that is allocated for each second of audio or video: if a song is encoded at 256 kbps, it means that for every second of audio 256 kilobits of information have been assigned (eye, which we are talking about kilobits, not kilobytes).
To determine how much information is going to be assigned to each second, there are mainly two methods: Constant Bitrate (CBR) and Variable Bitrate (VBR). As their names indicate, in the first one the data assignment is done in relation to a constant measurement, that is, if we want to obtain an audio file at 320kbps, the codec will assign this amount of data to every second of the song, without import its level of complexity (it is different to compress the acoustic information of a silent passage or one with many instruments playing simultaneously). The VBR method works in another way: quality is prioritized, so the amount of data to be assigned depends on the complexity of the piece of song being encoded. For example, in a part where there is silence, less information will be assigned, while in a part that for example has sounds of trumpets, violins, etc., the assigned information will be greater; Of course this range is determined by certain parameters.
There is a third method, “Average Bit Rate” (ABR), which is not so much a different method but rather a mixture of the previous two: a certain Bit Rate (a certain amount of kbps) is set, the which would be the average Bit Rate that will be assigned to the fragments of the file to be processed.
MP3: MPEG Audio Layer 3
For many reasons (and even when there are many arguments against it), MP3 is the king of lossy audio compressors. It is so widely known that it hardly needs an introduction, it has been going around a lot of time, and although many competitors (some of them very good) have come to the fore, its end is not seen at all near.
MP3 was born in 1987, mainly thanks to the research of the Fraunhofer Institute for Integrated Circuits IIS. In 1995 the files generated with this codec began to carry the extension .mp3, name with which this specification was popularized.
The rise of the internet and this format went hand in hand: the explosion of Napster and the P2P exchange programs during the second half of the 90s can be counted as one of the most important causes for the development of the network.
As of 2002, a series of competitors began to emerge, which have slowly caused this format to have lost some ground against formats such as AAC and WMA (introduced and backed by brands such as Apple and Microsoft, respectively), although it remains As the leader in presence.
Pros:
It requires little processing power for reproduction.
It is widely known, so there is a wide range of decoders
It is an ISO standard, part of the MPEG specification
Easy adjustment of compression quality, there are several options depending on whether you decide to privilege the resulting size or audio quality
Most (all?) Of today’s computers come with software to play MP3s, as well as the wide range of portable players
Cons:
Performance / efficiency lower than more modern codecs
There are no implementations for multiple channels (cannot generate 5.1 audio, for example)
The maximum bitrate (320kbps) is sometimes not enough
Unusable for high definition audio
