D
deleted user 10898
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με την δυναμικη εισοδο των νεων ψηφιακων φορμα αρχισα να ψαχνομαι λιγο με βαση προτροπη φιλου τεχνικου για τα λεγομενα "marketing bits" και το attenuation στο ψηφιακο domain.
αντιγραφω κατι πολυ ενδιαφερον απο το site της psaudio.
γραφει ο Dan Lavry!
Along with Paul's very good answer here are some replies from Dan Lavry on his forum regarding 24 bit recordings. It explains very well why you will be able to listen to 24 bit recordings and use a digital volume control without loosing any resolution, you have enough bits to throw on volume control:
"There are some practical reasons why we like to use binary numbers for digital electronics. And there are reasons (some are “historical” now) why we often use them in multiples of 8 digits, which is called a byte. So one byte is 8 bits. One can use 2 bytes for a 16 bit binary number, which was sufficient for a CD red book format (16 bits). But as soon as we wanted better resolution, it was “natural” to add a byte which makes 24 bits.
So an improvement from say 16 bits to 17 bits performance already called for handling 24 bits. It does not harm anything because we are not handling the data a bit a time, we are handling it in multiples of 8 bits…
But that practice make a 17 bit audio data into a 24 bit data? Performance wise, using 24 bit data to express 17 bit audio means you have 17 good bits and 7 useless bits. The useless bits can be set to zero, they can be “jumping around randomly”… they do no harm and they do no good.
In the case of 18 good bits, your 24 bit data has 18 good bits and 6 useless bits.
In the case of 20 good bits, your 24 bit data has 20 good bits and 4 useless bits.
And so on.
So in all cases of 17-24 bits you do have 24 bits. Some carry the audio. I call the useless bits “marketing bits” because the concept of 24 bits is often misrepresented or at least misleading.
If I sold you a 12 cylinder car, with only 8 cylinders connected to the drive shaft, do you have a 12 cylinder car? Is it an 8 cylinder car?
One way to determine if a bit is a good bit (containing valuable data, not “junk”) is to make sure that it contributes about 6dB to the performance (such as improved dynamic range and improved distortions). The simple way to look at it is 6dB dynamic range per good bit. So say you have 20 good bits, then you expect approximately 6*20 = 120dB dynamic range (unweighted measurement). A 16 bit format, assuming all the bits are good yields about 6*16 = 96dB. So 24 good bits would yields 144dB dynamic range.
But, there is no gear capable of 144dB dynamic range. In fact, very rarely can we reach 20 bits. Take any micpre, set the gain to 40, and you are no better then 18 bits because the noise coming into the AD is already high enough to “overpower” the lower 6 bits…
Of course, we also do not need 144dB. We can not hear that much range.
So 24 bits does not really describe the audio quality. It is always less then 24 bits, almost always less then 18 bits, rarely as good as 20 bits…
The data may be 24 bits, but the lower bits are useless, because they carry no music, only noise. The "real bits" are the bits that carry the music.
The marketing "definition" of 24 bits is based on the fact that there are 24 bits there. Using such "definition" I can make you a 124 bits audio gear. All you need is to add 100 bits of random noise on the least significant side (bit 25, bit 26....). Will it improve anything? No way. It will just cost you in data size (storage space...).
The reason we have 24 bit standards is due to the fact that we like to deal with bytes (multiples of 8 bits such as 16 bits, 24 bits, 32 bits...). That is why going from say 16 bits to 17 bits already called for 24 bits (with 7 bits not really used thus "wasted").
I am of course taking about the conversion, and the final outcome (CD, DVD and so on). One needs a lot more bits in the digital world, inside the computer, for signal processing in a DAW. Signal processing bits is a different subject, and it does not yield better resolution then the converters do.
In fact, most of the limitation in dynamic range, thus "real bits" is "cast in stone" by the time you come out of the mic[pre. There is hardly any musical material out there with 120dB dynamic range, which is near 20 bits.
I am not suggesting that multitracks should be limited to 16 bits. I am suggesting that there is no real audio chain in real life situation (mic, mic pre and AD) out there that goes over 20 real bits. So under the best of conditions, the last 4 bits are of no value. That is why I said “there is no such thing as 24 bits performance”."
αντιγραφω κατι πολυ ενδιαφερον απο το site της psaudio.
γραφει ο Dan Lavry!
Along with Paul's very good answer here are some replies from Dan Lavry on his forum regarding 24 bit recordings. It explains very well why you will be able to listen to 24 bit recordings and use a digital volume control without loosing any resolution, you have enough bits to throw on volume control:
"There are some practical reasons why we like to use binary numbers for digital electronics. And there are reasons (some are “historical” now) why we often use them in multiples of 8 digits, which is called a byte. So one byte is 8 bits. One can use 2 bytes for a 16 bit binary number, which was sufficient for a CD red book format (16 bits). But as soon as we wanted better resolution, it was “natural” to add a byte which makes 24 bits.
So an improvement from say 16 bits to 17 bits performance already called for handling 24 bits. It does not harm anything because we are not handling the data a bit a time, we are handling it in multiples of 8 bits…
But that practice make a 17 bit audio data into a 24 bit data? Performance wise, using 24 bit data to express 17 bit audio means you have 17 good bits and 7 useless bits. The useless bits can be set to zero, they can be “jumping around randomly”… they do no harm and they do no good.
In the case of 18 good bits, your 24 bit data has 18 good bits and 6 useless bits.
In the case of 20 good bits, your 24 bit data has 20 good bits and 4 useless bits.
And so on.
So in all cases of 17-24 bits you do have 24 bits. Some carry the audio. I call the useless bits “marketing bits” because the concept of 24 bits is often misrepresented or at least misleading.
If I sold you a 12 cylinder car, with only 8 cylinders connected to the drive shaft, do you have a 12 cylinder car? Is it an 8 cylinder car?
One way to determine if a bit is a good bit (containing valuable data, not “junk”) is to make sure that it contributes about 6dB to the performance (such as improved dynamic range and improved distortions). The simple way to look at it is 6dB dynamic range per good bit. So say you have 20 good bits, then you expect approximately 6*20 = 120dB dynamic range (unweighted measurement). A 16 bit format, assuming all the bits are good yields about 6*16 = 96dB. So 24 good bits would yields 144dB dynamic range.
But, there is no gear capable of 144dB dynamic range. In fact, very rarely can we reach 20 bits. Take any micpre, set the gain to 40, and you are no better then 18 bits because the noise coming into the AD is already high enough to “overpower” the lower 6 bits…
Of course, we also do not need 144dB. We can not hear that much range.
So 24 bits does not really describe the audio quality. It is always less then 24 bits, almost always less then 18 bits, rarely as good as 20 bits…
The data may be 24 bits, but the lower bits are useless, because they carry no music, only noise. The "real bits" are the bits that carry the music.
The marketing "definition" of 24 bits is based on the fact that there are 24 bits there. Using such "definition" I can make you a 124 bits audio gear. All you need is to add 100 bits of random noise on the least significant side (bit 25, bit 26....). Will it improve anything? No way. It will just cost you in data size (storage space...).
The reason we have 24 bit standards is due to the fact that we like to deal with bytes (multiples of 8 bits such as 16 bits, 24 bits, 32 bits...). That is why going from say 16 bits to 17 bits already called for 24 bits (with 7 bits not really used thus "wasted").
I am of course taking about the conversion, and the final outcome (CD, DVD and so on). One needs a lot more bits in the digital world, inside the computer, for signal processing in a DAW. Signal processing bits is a different subject, and it does not yield better resolution then the converters do.
In fact, most of the limitation in dynamic range, thus "real bits" is "cast in stone" by the time you come out of the mic[pre. There is hardly any musical material out there with 120dB dynamic range, which is near 20 bits.
I am not suggesting that multitracks should be limited to 16 bits. I am suggesting that there is no real audio chain in real life situation (mic, mic pre and AD) out there that goes over 20 real bits. So under the best of conditions, the last 4 bits are of no value. That is why I said “there is no such thing as 24 bits performance”."
