CD-quality Audio hardware and Software
For digital devices, the technical sizes of the Audio CD to keep in the rule, to justify the term "CD-quality". Occasionally, the term "CD-transparency" use. The following technical variables play a role:
- The Audio CD is standardized, and since the 1980s, so common that it is often used as a Benchmark, i.e. as a point of comparison,.
- Audio CDs have two PCMchannels.
- Each has a Sample Rate of 44,100 Samples per second, that is, 44.1 kHz.
- Each Sample is encoded with 16 Bit sample depth. The dynamic range, i.e. the maximum noise is 93 dB.
- In the case of digital devices CD-quality is 44.1 kHz with 16 Bit. This is a data rate of 1411.2 Kbits / s.
- Common terms in order to bring a Superiority over CD-quality to the expression, are "DVD-quality" and "Studio Master". These often describe a sample rate of 48 or 96 kHz and a sampling depth of 24 Bit.
- It is important in the case of "CD-quality" that all frequencies up to 22050 Hz. Many microphones, phones and speakers fail. You can only record a narrower range of frequencies, transferred, or re-enter.
- For analog devices, Stereo-quality assumes that the frequency and phase response throughout the audible frequency range is smooth, and the dynamics with the accuracy of CD is comparable. This is a signal to noise ratio of about 93 dB and an accuracy of ± 0.5 dB.
CD-quality Audio Codecs
For lossy AudioCodecs, like MP3, AAC, AC-3 and ATRAC, were extensive listening tests performed to demonstrate, what is the compression rate for CD quality is achieved:
- In the case of Audio CDs, all the frequencies from 0 to 22050 Hz with a sound pressure level accuracy of ± can be played 0.5 dB. Under Ideal conditions, the sound pressure level change of about 0.3 to 1.5 dB are barely perceptible.
- CD quality means that all audible frequencies are reproduced without perceptible amplitude error or distortion over a Dynamic range of up to 93 dB. This is significantly greater than the average dynamic range of music, and language.
- CD quality refers in this case to the auditory perception. Compares the audibility of artifacts, i.e. noise, interference or distortion, as well as spectral, temporal and dynamic deviations from an Original in the technical CD-quality.
- Nonspatial aspects, such as the localization, the perceived source extent or the so-called "Eingehülltheit be compared" with spatial sound.
- Voice Codecs such as GSM, CELP, G. 711, and in telephony the use of the usual compression rates for good speech intelligibility. You are but far below CD-quality sound, sometimes narrow and clearly distorted.
- Also, records do not have CD-quality, as we do in this practice tip will discuss at length.
- The Audio-Codec MP3 has data rates of approximately 128 kbps CD-quality. This is a compression rate of 1:11. Experienced listener and especially dynamic music demand higher bit rates.
- AAC and the MPEG-H Audio Codec still need lower bit rates to however, CD-quality exhibit.
- Lossless Codecs such as FLAC and ALAC preserve the quality. If the source material is CD-had quality, also has CD-quality.
A comprehensive comparison between Audio Codecs, like MP3, AAC, WMA, and OGG, you will find in a further CHIP Online article.