Tilføjelse: I Audirvana har jeg følgende indstillingsmuligheder for iZotope konverteren (fra manualen):
Sample Rate ConversionSample Rate Conversion happens when
- The audio device does not handle the audio track sample rate
- Upsampling is forced to either oversampling to 2x or 4x the track native sample rate or to the audio device maximum sample rate.
Two different Sample Rate Converter algorithms are proposed: the standard Apple CoreAudio, or the gold standard iZotope 64-bit SRC.
Sample Rate Converter SettingsUse the quality slider to set the desired quality level.
Note that with high initial sample rates, the best quality setting (especially for Apple CoreAudio) may be demanding too much computing power for some Macs (thus giving in playback pauses).
For iZotope 64-bit SRC, you have access to advanced detailed parameters to tune the sample rate converter filters:
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Steepness: steepness of the transition band of the lowpass filter. Higher steepness will reject unwanted frequencies but cause more ringing in the timedomain and a higher CPU load
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Max filter length: controls the memory (and CPU usage) used by the resampling filter. Default value (500k) should be sufficient for most applications. Can be increased for getting vey high quality output for very high sample rates (e.g. DSD downsampling)
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Cutoff: cutoff frequency is computed by multiplying the Nyquist frequency by the value of the cutoff scaling parameter. Larger values of cutoff scaling offer a flatter pass-band, while smaller values offer better aliasing suppression
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Anti-Aliasing: the amount of suppression in the lowpass filter’s stop-band. Any frequencies in the stop-band, which are not fully attenuated, will result in aliasing, which is when these unwanted frequencies are mapped to different frequencies and mixed into the output. Use higher values for better quality and use lower values to minimize CPU load.
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Pre-ringing: all lowpass filters are characterized by the amount of ringing they introduce into their output. The steeper the filter, the greater the amount of ringing. There are two general types of ringing: pre-ringing and post-ringing. Preringing will smear transients earlier in time, while post-ringing will smear transients later in time. This control allows users to select pre-ringing, postringing, or anywhere in between. A value of 1.0 produces a linear phase filter with equal pre- and post-ringing. A value of 0.0 produces a minimum phase filter, which offers no pre-ringing but has non-linear phase distortion, which can be objectionable. Setting intermediate values allows a continuous tradeoff between pre-ringing and post-ringing and allows users to linearize phase in the pass-band as much as possible.