Is bit depth about dynamic range or data?

[fas42]

Bit depth is about the signal to noise ratio. If you reduce the depth, you get a higher level of random noise - tape hiss is the obvious analogue variant. A decent digital encoding can capture that tape hiss with ease, so "everything that matters" is being transferred

 

This all assumes that the person who might be playing around with bit depth, while recording and/or mastering, knows how to apply the correct dither, at the correct point of operations ... get it wrong, and you can hear the mistake.

 

Human hearing can compensate for random loss of data, or excess noise, remarkably well - good handling of digital data can rely on that ability, to make even poor bit depth "sound OK".

 

Dynamic range is purely about mastering decisions - nothing to do with bit depth.

[fas42]

With regard to recording, if one can guarantee in advance that the sound levels of the music happening will only reach a precise maximum value, and you adjust the recording chain in advance to neatly peak in level for that exact value, then 16 bits will be fine. But in the real world of music making, this would never work - musicians become passionate, and easily go much higher in a transient peak - you want headroom in recording, to make sure that the recording never clips; digital is far less forgiving than analogue tape. Reduce gains in the recording chain to give some margin for this, and then you are not using the full 16 bits to capture the performance - 24 bits is a nice number for the technical side to use; you will never use that full 24 bits, but the 16 bits you're really after can be comfortably surrounded by "insurance" bits. And then when you do editing then you want maximum precision in the mathematical handling, so no matter how much you attenuate or amplify to get the sound you're after, nothing gets lost or degraded doing these operations - high precision is cheap to do these days, so the bigger the numbers which are used, 32, 64, etc, the better.

 

Only when all that is done, and you are ready to produce the output which the consumer will see, do you produce the 16 bit version - this can be neatly fit into that range - and that will have all the musical detail that matters.

 

Agree about tape hiss - human hearing can discard its presence when the playback is "in the zone" - the very best reel to reel is only roughly equivalent to 12, 13 bits depth - which is why Dolby came into the picture.

[fas42]

2 minutes ago, mansr said:

Signal to noise ratio and dynamic range are the same thing.

 

Yes, if one is talking about it as a purely technical level concept - but dynamic range is thrown around these days as having subjective connotations - as in, "orchestral performances can't be captured by 16 bits, the sound is, too big!" ... I was referring to this subjective take on the matter.

[fas42]

5 hours ago, davide256 said:

bit depth does determine dynamic range. The CD 44.1khz sampling rate/16 bit dynamic range format was driven by commercial digital technology  practicalities of the 80s... it works most of the time but fails on complex music and music where there is significant content at dynamic range extremes. The later DVD format of 48/24 addressed the corner cases but I find that the early DVD recordings were focused on multichannel and had poor stereo versions. Higher sampling rates like 96khz and 192 khz seem to help in taming DAC digital artifacts.

 

 

 

And this is why I deliberately used the term "dynamic range" the way I did in my post above - there is a quite common belief that somehow 16 bits can't contain "high dynamic range", but this is purely an implementation problem in typical playback chains. The "failure" occurs because of, yes, digital artifacts, but this has nothing to do with the measurable technical performance of the DAC and associated circuitry; and everything to do with anomalies caused by inadequate engineering of the overall component, and system. These are unfortunately audible, and lead so many people to give, say, CD replay the thumbs down ... luckily, it turns out that careful tweaking can attenuate these issues sufficiently; but very few people are motivated to go to the lengths to achieve this. Other solutions are to buy very expensive bits of kit now which can deliver the "dynamic range" - or just wait until eventually everyday audio components are engineered well enough to do the job.

[fas42]

2 hours ago, audiojerry said:

 

But so far, I don't feel like my original question has been answered - at least to my benefit. As best as I can determine, bit depth captures both musical data and dynamic range - it is not exclusively one or the other. Part of my remaining confusion can be attributed to my conception of dynamic range. My simplistic view is that dynamic range is the range of loudness from the noise floor (zero) to the loudest peak in terms of spl.   

 

 

Where digital "gets it wrong" for many people in the real world of playback, is that critical information that is encoded at relatively quiet levels compared to the maximum signals that are occurring at the same time, is too distorted by imperfections in the playback chain to be easily discerned by the listening mind - people hear this all the time in sub-par systems; a track which is a complex mix of sounds is played, and it "sounds a mess!" ... the dynamic range is there, as a technical, measurable characteristic, but distortion of low level information is too great - and subjectively "you can't hear what's going on" ...

 

I recently posted a clip of a track from a Ry Cooder album, and the response was that it "just collapses into a bowl of mush" - this is a classic symptom of inadequate effective resolution of the playback chain; subjectively, the "dynamic range" is not good enough ... and this has absolutely nothing to do with the encoding using only 16bits.

[fas42]

7 minutes ago, sandyk said:

 

While I don't have too much of a problem with the first paragraph, if the posted clip was from YouTube, even most mediocre systems should have no problems playing virtually all YouTube Audio without any real problem.

 

 

Again, the posting of a YouTube clip is there as an easy way to reference the style of the music, etc - it wouldn't make sense to prove you how good my system was, by ringing you up on my old fashioned corded phone, and holding up the handset so that you could listen ... 🙂.

 

Played that CD of Ry Cooder a couple of visits ago to the local audio friend ... ummm, was not good - not a mush, but very dodgy on the ears, 😉.

[fas42]

21 hours ago, SJK said:

SNR has nothing to do with either bit depth or the frequency of a digital recording. There is no noise, at least not in digital terms. 
 

A digital recording captures the source, whatever that may be, the same as an analog recording and with consideration for the digital ADC front end.  
 

You make reference to tape hiss and yes, in an analog world there was great effort made to move as far away from the noise floor as possible.
 

I’m deeply confused as to how that relates to a digital recording with the two values under discussion - bit depth and frequency. 

 

 

 

A recorder will typically use as least 16 bits for recording, which means you won't hear noise, assuming decent settings - but there is nothing to stop one reducing the bit depth of that recording afterwards; which will introduce audible noise ... we have a basic, older digital camera which I once tried to use for capturing some playback; which was close to useless because the SNR was terrible; nominally 16 bits, but the automatic gain control was hopeless.

 

Modern devices are normally fine, but being careless, in a manner that compromises the bit depth, will certainly be audible.

[fas42]

I have an opera CD, which bugged me from the earliest days after I bought it - there was this peculiar noise, right at the beginning of the first track, which disappears quite quickly ... after many years I was in a position to rip that track, and study the waveform ...well, well - some dingaling had mucked up the transfer from tape; and it was quite obviously suffering from severe degradation from bit depth loss, for about 30 secs. The chap probably suddenly realised his mistake, and then set it correctly from then on - but never went back and fixed the opening bit ... poor mastering captured for eternity, set in plastic ... 😁