In this article we are going to address the audio coding settings that affect the sound quality. Understanding how conversion settings work can help you select the optimal sound coding properties in terms of file size relative to sound quality.
What is the bit rate?
The bit rate is the amount of data consumed to transmit the audio sequence per unit of time. For example, a bit rate of 128 kbps (kilobits per second) means that a second sound is encoded with 128,000 bits (1 byte = 8 bits). If you convert this into kilobytes, a second of sound occupies about 16 KB.
Therefore, the higher the bit rate of a track, the more space it will occupy on the computer. However, with the same format, a higher bit rate allows you to record the best quality sound. For example, if you convert an audio CD to MP3, the 256 kbps bit rate will provide much better sound quality than the 64 kbps bit rate.
Because today’s hard disk space is relatively cheap, it is recommended to convert to MP3 with a bit rate of at least 192 kbps or higher.
The bit rate can also be classified as constant or variable.
The difference between constant bit rate (CBR) and variable bit rate (VBR)
The constant bit rate means that the encoding of each audio segment consumes a constant amount of bits. However, the structure of the sound may be different, and the coding of a segment of silence requires much less bits than the coding of a segment of intense sound. Unlike the constant bit rate, the variable bit rate adjusts the quality of the coding at various intervals. Thus, intervals that are simple in terms of coding will use a lower bit rate, while more complex intervals will be coded with a higher bit rate. The use of a variable bit rate allows for better sound quality without increasing the file size.
What is the sampling frequency?
This term is used in the conversion of analog signal to digital form and defines the number of samples (signal level sample measurements) per second needed to convert a signal.
CBR vs VBR – which one to choose?
When you are going to pass a music CD to MP3 or AAC format you will have seen two different encoding options, the CBR and the VBR. Do you know the diference?
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CBR (Constant bitrate) encoding
CBR is a type of encoding in which a fixed bit rate is always used, so if we encode a song at 192 Kbps, the resulting file will have a bitrate of 192 Kbps for the entire duration of the song.
It is the speed at which data is processed or transferred.
It is usually measured in seconds and the most common units are:
Kb / s or Kbps (remember that the lower case “b” is bits, not bytes).
Mb / s or Mbps.
Also called: bitrate, bit-rate and BR.
The main advantage of using CBR is that the coding is a bit faster (compared to VBR). However, the resulting files are not as well optimized in size and quality.
CBR coding also has another advantage and we know in advance the transfer rate we need. For example, if we set a bitrate of 300 Kbps, we already know that with a 320 Kbps connection we will be able to transmit the data without suffering cuts, so it is usually used in real-time transmissions or streaming.
VBR encoding (bitrate variable)
VBR is an encoding method that allows a variable bit rate, this means that the bitrate of an audio file can increase or decrease dynamically depending on the complexity of the sound.
If the music is very simple or there is silence for a few seconds the bitrate can go down and then go back up in the more complex areas of a song.
