View Single Post
Old 2012-07-05, 01:27 PM
Re: 16 Bit vs 24 Bit

good hardware should be present, otherwise forget everything
in principle, a high resolution (24Bit/192kHz) is better than a low

wiki says:
Audio bit depth

In digital audio, bit depth describes the number of bits of information recorded for each sample. Bit depth directly corresponds to the resolution of each sample in a set of digital audio data. Common examples of bit depth include CD quality audio, which is recorded at 16 bits, and DVD-Audio, which can support up to 24-bit audio.Contents

Digital audio

A set of digital audio samples contains data that, when converted into an analog signal, provides the necessary information to reproduce the sound wave. In pulse-code modulation (PCM) sampling, the bit depth will limit signal-to-noise ratio (S/N). The bit depth will not limit frequency range, which is limited by the sample rate.

By increasing the sampling bit depth, quantization noise is reduced so that the S/N is improved. The 'rule-of-thumb' relationship between bit depth and S/N is, for each 1-bit increase in bit depth, the S/N will increase by 6 dB.[2][3] 24-bit digital audio has a theoretical maximum S/N of 144 dB, compared to 96 dB for 16-bit; however, as of 2007 digital audio converter technology is limited to a S/N of about 124 dB (21-bit)[4] because of real world limitations in integrated circuit design. Still, this approximately matches the performance of the human ear.[5][6]

Technically speaking, bit depth is only meaningful when applied to pure PCM devices. Non-PCM formats, such as lossy compression systems like MP3, have bit depths that are not defined in the same sense as PCM. In lossy audio compression, where bits are allocated to other types of information, the bits actually allocated to individual samples are allowed to fluctuate within the constraints imposed by the allocation algorithm.

Dynamic range

Dynamic range is the difference between the largest and smallest signal a system can record or reproduce. With the proper application of dither, digital systems can reproduce signals with levels lower than their resolution would normally allow.[7] Therefore there is not a direct connection between bit depth and dynamic range.

8-bit resolution, as found in older computers and audio samplers offers up to a 48dB dynamic range under perfect recording and reproduction conditions (roughly equivalent to standard-grade audio cassette tape, but with more obvious quantization errors at low volumes unless a deliberate 1-bit background noise "dither" is introduced, which provides a greater perceived dynamic range despite the noise floor being at approx -45dB), and 16-bit, as used in CD and modern equipment, can provide up to 96dB of dynamics (again, a deliberate noise floor may be introduced to soften perceived quantization error; however in this case, the floor is still below -90dB, which is quiet enough to become lost in circuit distortion in cheap players, or environmental background noise in all but the quietest rooms with the loudest playback volume). The 12- and 14-bit DV/NICAM standards (-72 and -84dB respectively) were thought to be perfectly adequate for televisual and video camera applications at the time of their inception, particularly compared to VHS and Hi-8.

Audiophile-spec recording resolutions extend this to a theoretical -120dB (20-bit) or -144dB (24-bit), the latter of which exceeds the dynamic range between complete silence (signal energy below that which can be detected by the human ear) and noise of high enough intensity to cause almost immediate ear injuries, with an ideal 24-bit DAC and associated amplifier being able to accurately output signal values from 0, 1, 2 through 16777213, 16777214, 16777215.


Standard DV audio is 12-bit (4096 levels), NICAM pseudo-14-bit (10-bit data + 4-bit gain signal, with 14-bit output DAC), CD and DAT audio is 16-bit (65536 levels), and enhanced CDs, SACDs and DVD-Audio can use 20 or even up to 24-bit sampling (>16 million levels). CD Audio has also left a lasting impression on computer and other digital audio applications, where 16-bit is the default "hi-fi" sample resolution (as opposed to earlier 8, 6 or even 4-bit efforts), with higher precision often considered the reserve of audiophiles as the representable range of intensities rapidly exceeds the theoretical limits of human perception, particularly when environmental noise is considered.

What is a 'bit' of data?

In computing parlance, bit is the abbreviation for a single binary digit, represented by a 0 or a 1. A word is a binary number with more than one digit. Binary numerics are base-2; thus, each digit can only be a 0 or a 1. In comparison, traditional decimal numerics are base-10, having digits that can only be 0 through 9. For example, the 16-bit binary number 0110111110111010 is equivalent to the 5-digit decimal number 28602. The number of bits per word is simply how many digits there are in the corresponding number. The words in commonly used PCM digital audio formats are 8, 16 or 24 bits long. Larger words have higher resolution. The resolution of a 16-bit system can be calculated by using 216 which gives a value of 65,536. A 24 bit system (224) has a resolution of 16,777,216.

Bit rate

Bit rate refers to the amount of data, specifically bits, transmitted or received per second.

One of the most common bit rates given is that for compressed audio files. For example, an MP3 file might be described as having a bit rate of 160 kbit/s or 160000 bits/second. This indicates the amount of compressed data needed to store one second of music.

The standard audio CD is said to have a data rate of 44.1 kHz/16, meaning that the audio data was sampled 44,100 times per second, with a bit depth of 16. CD tracks are usually stereo, using a left and right track, so the amount of audio data per second is double that of mono, where only a single track is used. The bit rate is then 44100 samples/second x 16 bits/sample x 2 tracks = 1,411,200 bit/s or 1.4 Mbit/s.

This explains why, for example, a Minidisc recorder, which uses ATRAC compression, can store files lasting twice as long on a disc, if the default, recording in 2 channel stereo, is set to single channel mono recording.

To fully define a sound file's digital audio bit rates: the format of the data, the sampling rate, word size (bit depth), and the number of channels (e.g. mono, stereo, four-track), must be known.

Calculating values

An audio file's bit rate can be calculated given sufficient information. Given any three of the following four values, the fourth can be calculated.
Bit rate = (sampling rate) (bit depth) (number of channels)

E.g., for a recording with a 44.1 kHz sampling rate, a 16 bit depth, and 2 channels (stereo):
44100 16 2 = 1411200 bits per second, or 1411.2 kbit/s

The eventual file size of an audio recording can also be calculated using a similar formula:
File Size (Bytes) = (sampling rate) (bit depth) (number of channels) (seconds) / 8

E.g., a 70 minutes long CD quality stereo recording will take up 740880000 Bytes, or 740 MB:
44100 16 2 4200 / 8 = 740880000 Bytes

by the way: Neil Young prefare VINYL or bd audio with 24Bit/192kHz
he said, cd audio is shit!

Reply With Quote Reply with Nested Quotes