Is anyone using anything higher than 128kbps/44.1mhz for spot production?
SirRoxalot said:I thought that I'd chime in just to make sure that everybody understands how bit rates are derived.
The rule is that it requires two samples to determine the wavelength (frequency) of a sample. If you sample at 44,100 samples per second, the highest frequency you can determine is 22,050. If you want to accurately represent the amplitude (volume level) of the sample, you'll need more than two samples. Lower frequencies, with longer wavelengths, will be more accurately represented than higher frequencies. Some sampling schemes try to even out this differential by using different scales along the Y-axis to determine amplitude.
The bit rate is determined by multiplying the sampling rate (ex. 44,100 samples/sec for CD quality) x the quantization type (the largest binary number available to describe the amplitude (volume) of an audio sample).
For example, 16-bit audio gives you levels from 0000000000000000 to 1111111111111111 in binary, or 0 - 65534 in decimal. 44,100 sample x 16 bits/sample = 705600 bit/sec., or 705.6 Kbit/sec.
Compression algorithms like MP3 offers varying compression rates. There are also other factors, like how the samples are compressed, and whether compression is at a constant or variable bit rate. The MP3 standard allows quite a bit of freedom with encoding algorithms, and different encoders output different quality, even at similar bit rates.
If you're streaming MP3s at 128K, you're compression ratio is 705.6/128 = 5.125:1. That, of course, doesn't take into consideration the quality of the encoder.
To quote Frauhofer IIS:
In listening tests, MP3 encoders have performed significantly worse than those using more modern compression methods (such as AAC) at low bit rates. In a 2004 public listening test at 32 kbit/s[5], the LAME MP3 encoder scored only 1.79/5 - behind all modern encoders - with Nero Digital HE AAC scoring 3.30/5.
The bottom line is the surfer's motto: There ain't nothin' like a good .wav.