Dither is needed even when doing just resampling, as long as the output format is 16 bit. Internally, SSRC uses higher precision, and dither is advisable co convert to this higher internal precision to 16 bit at the final stage.Same as with decoder output at MAD or FB2k.
Anyone know if there's a version of SSRC that supports 32-bit ?
Often I work in Cool Edit Pro in 48kHz / 32-bit and then downsample to 44.1kHz / 16-bit. I'd like to do this last step in SSRC, though, since SSRC seems to be faster and from what I heard might be better than Cool Edit Pro's resampling.
I have been wondering, though. What are the optimal settings in both Cool Edit Pro and SSRC for downsampling from 48kHz / 32 (or 24) bit to 44.1kHz / 16bit?
Also, when editing in Cool Edit Pro, the manual advises that you should convert 16-bit audio to 32-bit audio, do all the editing, and then convert back to 16-bit. Is this optimal?
If so, does the 16-bit to 32-bit change require any special settings?
I have an idea how to detect if there's quantization distortion, but how do you test/find out if there's noise modulation?
About SSRC KikeG already answered, you can use the same settings in CEP (at least for flat dither): Pre-/Postfilter enabled, quality 600, Dither Depth 0.9, p.d.f. Triangular, No Noise Shaping. If you use other noise shaping types (e.g. 44.1 kHz shaped), you'll get even less audible noise added. All settings should be the same except Dither Depth which will be different for each noise shaping type and needs to be tested.
QuoteI have an idea how to detect if there's quantization distortion, but how do you test/find out if there's noise modulation?Generate a 32 bit -90 dB very slow sinewave, for example 0.3 Hz, then dither to 16 bit. Convert again to 32 bit, amplify it up to audible levels, and play. If you notice how the background noise changes in level or in tone, then there's noise modulation. Most obvious case is when noise dissapears when the waves is near crossing the 0 point.
For real music - is this really important / does it make a difference? Could you please explain and/or point me to some more information about this?What about applying a ~10Hz highpass before 32->16bit+dither: Would this avoid/decrease noise modulation on lower dither depth?
[EDIT]Thanks for your answer BTW [/EDIT]Happy to help
You should use 1-bit of dither, not 0.9 bits of dither, when converting without noise-shaping.2-bits peak to peak (which equals 1-bit RMS - which is what these programs take as input) triangular dither is mathematically proven to remove 100% of the distortion and noise modulation.
... I don't claim you'll hear a difference but I don't think the (probably inaudible) decrease in noise due to 0.9-bits compared to 1-bit is worth risking the (probably inaudible) increase in distortion or noise modulation.
It's certainly not worth going back and re-processing anything you've done previously - the effects are an order of magnitude smaller than the smallest problems you find in lossy audio codecs. But, for once, there is an objectively "as-near-to-perfect-as-possible" way of doing things, so you might as well use it.
You should use 1-bit of dither, not 0.9 bits of dither, when converting without noise-shaping.
If dither depth is near 1 (e.g. 0.99) the distortion will be masked by dither noise, so it's there but audible.
However, I don't buy this argument from a mathematical view-point. From a practical view point, there may be many cases where it sounds better not to dither at all, but that's a largely subjective issue...
QuoteIf dither depth is near 1 (e.g. 0.99) the distortion will be masked by dither noise, so it's there but audible.Did you mean "inaudible"?
For 16-bit sources which were correctly dithered to start with, there's an argument that they are already self dithering when resampled or re-coded. However, I don't buy this argument from a mathematical view-point.
... In that case, using exactly 1-bit, it isn't there at all. It's not that it's masked, it's that it isn't there.
But, as you suggest, if it's perfect with 1-bit of dither, and it's a disaster with 0 dither, then there must be a sliding scale in between. If there's a compromise between (inaudible) noise and (inaudible) distortion, I'll take the noise. Mainly because digital distortion (rather than analogue distortion) is hated by the human ear, whereas noise is easily ignored.
This may or may not convince you:http://mp3decoders.mp3-tech.org/24bit2.html#dither
ATH shaped is only the best for a noise free recording, which is practically not possible.For noisy recodings you must calculate the noise shaping floor from the ATH and the noise floor of the recording. For very high noise floors the optimum is the shape of the noise floor.