Quote from: knutinh on 27 February, 2008, 04:43:22 AMCautionIs it concievable that the 24bit version might sound different but worse than dithered 16bits in some PCs if 24 bits was truncated to 16 bits by soundcard/OS?Good point. Any playback chain that is not capable of processing 24 bits correctly is not suitable for this kind of testing.
CautionIs it concievable that the 24bit version might sound different but worse than dithered 16bits in some PCs if 24 bits was truncated to 16 bits by soundcard/OS?
Sorry for interrupting your conversation, but I don't want to create another topic only for this:I would like to know if there is any difference in playing 16bit lossless file with 24bit or 16bit output format (i use foobar). Is there also a difference (degreed/improved/same quality) for lossy formats? And while my card support 24bit output, should I use it instead of 16bit. Almost all my files are 16bit flacs, but I need some space so I'll rip my cds with mp3 until I get a new hdd.
Quote from: Kees de Visser on 27 February, 2008, 05:51:34 AMQuote from: knutinh on 27 February, 2008, 04:43:22 AMCautionIs it concievable that the 24bit version might sound different but worse than dithered 16bits in some PCs if 24 bits was truncated to 16 bits by soundcard/OS?Good point. Any playback chain that is not capable of processing 24 bits correctly is not suitable for this kind of testing.An you should prove the playback chain is really 24 bit capable (ie not rely only on the specs of the hardware/software).
Being a newcomer to this site, I’ve only now read some of the other threads on the 24 vs 16 bit debate. I’ve also now read some of the material on the complex subject of dithering.Before submitting any sample of 24-bit audio that contains a section that can be demonstrably distinguished from 16 bits (testing with ABX software), I’d just like to check on the ground rules for such an exercise.Question 1:Given that it can be demonstrated (using low level test tones) that artefacts in a 24-bit to 16-bit conversion are more evident if dithering is not used, and given that dithering is widely in use and recommended, is the use of some form of dithering compulsory for this exercise? If it is not compulsory, then I might seek to identify a sample where artefacts were in evidence.
Question 2:If the answer to question 1 is that dithering is compulsory, or at least acceptable, and given that dithering introduces an amount of noise, does this exercise exclude from consideration simpler forms of dithering that introduce much more noise than is necessary? More specifically, are any of the dither methods available with readily available software such as Audacity or foobar acceptable for this exercise? If acceptable dithering method(s) can be indicated, I would seek to identify a sample where the noise of the dithering is detectable when comparing a derived 16-bit version with a 24-bit original.
Substituting a slightly different (and much simpler!) question, for sine waves with no direct current offset and which are at a frequency not far below half the sampling rate, the maximum [peak] amplitude that can be represented either side of zero is half of 2^16 , and the minimum [peak] amplitude that can be represented either side of zero is 1. Half of 2^16 is 32768. Voltage ratios can be expressed in decibels using the expression 20 x log (voltage ratio). That gives us the figure 90.3 dB as the ratio between the peak level of the loudest sine wave and the softest [highly imperfect] representation of that sine wave without dither. The low level wave doesn’t really have a shape to make the description ‘peak’ meaningful, being some variety of rounded square wave. And the filtering needed might alter the peak value of the low level ‘sine wave’ somewhat.
I'd like to remind you that there's a free tool around for requantization, dithering and noise shaping that supports arbitrary bit depths and custom noise shaping filters: NOISE
However, I did include the necessary basic conditions in the first post: a properly resample to 16 bit version of same
~ Not applying the optimal type of dither before performing such a test would seriously call into doubt the validity of the results.~ If your hypothesis is "reduction of 24bit music samples to 16 bits using X technique is not transparent", then you can use any kind of dither available. Note that confirmation of the second hypothesis is still useful.
~ It may be possible, using poor quality dithering, with no noise shaping or poor noise shaping, to make an audible difference because of the added noise. That is not "properly" done. Many people here will remember that in the recently published year long ABX test of DVD-A & SACD vs resampled to 16 bit, the only differences detected by anyone were the "silence" between tracks, turned up to extremely high levels, where the unshaped dither used in their resampling was audible.Proper resampling means, to me, what CoolEdit/Audition does with resampling, dithering, and noise shaping. I won't go into the evidence that has been presented in various places, but the program's resampling is probably as good as it gets. ~
When I first used a 24-bit audio card, a few years ago, for capturing amateur musical performances, I could immediately detect the improvement compared with capturing with a 16-bit sound card.
If I am to pursue this further, I will probably need to concentrate on other artefacts than noise, though the more I read, the less optimisitic I am of success.
I'd also mention that once I had a 24-bit card available I no longer sought to make recordings at close to clipping level, but allowed the recordings much more headroom.
With proper dither, there will be no artifacts other than noise.
QuoteWhat is the effect of a non-white random source in dithering?I did a small and free software to show/hear the effect of dither. The dither itself can be noise but also a sine wave. So you can try and listen to the result.Get it here
What is the effect of a non-white random source in dithering?
Quote from: cabbagerat on 03 March, 2008, 09:23:12 AMWith proper dither, there will be no artifacts other than noise.If I am not mistaken, that is the question we are trying to resolve, whether the arte[/i]facts that can be heard (even with optimal dither) when test tones are used, set at very low levels, and listened to at a high gain setting, can also be heard by the human ear at realistic listening levels, with music.
~ Well, if that's the question, then to my mind it's already been resolved for 24bit -> 16bit conversions. Consider our 24bit music samples x[n] and dither signal d[n]. Now, we define e[n], which is the difference between the x[n] and quantize_to_16bits(x[n] + d[n]). Ok? ~
Voxengo's software says that 8-, 16- and 24 bit output is dithered with a gaussian noise and a slight noise-shaping. I have no idea if it is the proper way to do it.
Quote from: Pio2001 on 26 November, 2008, 04:25:42 PMVoxengo's software says that 8-, 16- and 24 bit output is dithered with a gaussian noise and a slight noise-shaping. I have no idea if it is the proper way to do it.The shape of the dither is quite significant. I'm not sure a "slight" noise-shaping is sufficient. I respect the difficulty in obtaining these results. However, I am afraid that all they show is that this dithering algorithm is discernible from the high-resolution original. If I were to perform this test, I'd try it with foobar2000's dither.Nonetheless, thank you for the results. As I've always considered 24/96 to be excessive, you've given me a point to ponder.
I got 10/10 in the ABX test, with closed headphones, listening to the initial fade-in.
There are real differences between 16 bit and 24 bit files, just as there are real differences between uncompressed and mp3. As with the differences between wav and mp3, 16 bit vs 24 bit is often difficult to identify by listening.Test signals are one thing, but has anyone found any 24 bit music recording that can be successfully identified via ABX testing against a properly resample to 16 bit version of same?