Bit rate

Media players often report the bitrate of the audio file playing.

 

1411 kbits is the value you will see when playing CD quality audio using an uncompressed lossless format like WAV.

The calculation is simple;

Number of Channel *  word length * sample rate

Playing CD quality is playing 2 channels with 16 bit word length and 44100 samples per second or 2*16*44100=1411200 bit/s or 1411 kbs.

 

The bit rate of the audio file says nothing about what is send to the DAC.
If you use up-sampling e.g. set Win to output 24 bit at 96 kHz, you still see 1411 kbs but you are sending 2*24*96=4608 kbs to the DAC.

 

If you play FLAC you see most of time a value between 700 – 800 as FLAC compresses 40-50%.
This is the bit rate of the compressed file.
However it is lossless so when expanded to raw PCM you have the full unaltered original 1411 kbits.

The bit rate of a lossless compressed format indicates the amount of lossless compression.

In case of MP3 the bit rate tells us how much of the original information is discarded.
Indeed MP3 is like magic, using e.g. 320 kbs and compare this with FLAC (or any other lossless compression)  the bit rate is halved and so is the file size. Still most of us will not hear a difference between the two.

Not to be mistaken for an absence of differences.
They are there but very subtle.

If you want to hear them you do have to hunt for them e.g. music by Kraftwerk.

The bit rate of a lossy file indicates the amount of information discarded.

 

Why do they use the bit rate of the file instead of the actual playback rate?

The answer is simple, the actual rate is not very informative.
You rip a CD to WAV, FLAC and 320 CBR MP3.
To play them they must be converted to something a DAC does understand, raw PCM.
This will yield the same value regardless of the file format e.g. 1411 kbs in case of 2 channel 16 bits 44.1 kHz audio.