This module has been developed for casual users to overide re-sampling parameters of AudioFlinger (the system-wide mixer) in my other modules ("Audio misc. settings" and "Hifi Maximizer") so as to significantly improve audio quality of LDAC Bluetooth earphones and DAC's under $30 (probably) especially when replaying 44.1 kHz tracks up-sampled over or equal to 96 kHz & 24 or 32 bits by AudioFlinger, but also the quality of internal speakers and a 3.5 mm jack receiving 48 kHz & 24 or 32 bits audio data (except 48 kHz & 16 bits) up-sampled by AudioFlinger. If you are an audiophile expert, please use "extras/change-resampling-quality.sh" in "USB SampleRate Changer" which can change the parameters on the fly flexibly.
By the way, although most people might wonder how this module improve the audio quality of such devices, it is accomplished by very long filter length re-sampling near ideally (almost without pre-echo, ringing (post-echo) and aliasing noise) cutting off a frequency zone from just above 20 kHz filled with ultrasonic noise generated by high frequency dithering and deteriorating audible sound by intermodulation significantly amplified by large amplification non-linearity of LDAC Bluetooth earphones and DAC's under $30. Furthermore this can be considered to be a kind of decimation filtering from 44.1 kHz & 16 bits samples to 40 kHz & 24 or 32 bits ones except the ultrasonic noise by hight frequency dithering. So it has little effect when using AAC and SBC codecs which transmit audio data by 44.1 kHz & 16 bits.
However, as the noise has a merit adding mellowness into audible sound in the case of none cheap DAC's having very small amplification non-linearity, please use this module only when using LDAC Bluetooth earphones (any devices, as far as I know) and DAC's under $30 (typically using DAC chip CX31993, ALC5686, KT0210, etc.).
Finally, this module is designed to override re-sampling parameters set by my other modules, but can be used by itself only. You can install this module and enjoy its effect whether you are using one of them together or not.
Notes:
- If you feel your LDAC earphones or "cheapie" DAC wouldn't become to sound good at all, try editting "service.sh" script in the installed place or its ZIP archive so as to replace "94" in it with one of "93" down to "87" for appropriately cutting off ultrasonic noise causing intermodulation.
- This module doesn't have the effect for Hires. tracks (greater than 44.1 kHz sample rate) which not having large pre-echo and ringing, and high frequency dithering noise, except ultrasonic noise added on purpose for mellowness. Anyhow, if you want to improve the quality of only Hires. tracks on "cheapie" devices, edit "service.sh" script in the installed place or its ZIP archive as described in the script.
- LDAC earphones and DAC's deteriorate the quality more or less by their internal over-sampling filtering when receiving low sample rate data.
- Don't forget disabling "A2DP hardware offload" on Snapdragon devices (if you can), because it forces double re-sampling (44.1 kHz to 48 kHz, and 48 kHz to 96 kHz) and it is so much worse that the latter re-sampling guts the former one at all.
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Appendix A. Examples of Re-sampling Parameters :
Stop band attenuation (dB) Half filter length Cut-off (%) Stop band (%) Memo AOSP parameters: - - - - 90 32 100 Default Quality 80 16 100 LOW Quality 84 16 100 MED Quality 98 32 100 HIGH Quality Parameters of Audio misc. settings: - - - - 159 480 92 Old devices of A11 and earlier 165 360 104 Low performance devices of A12 and later with audio ones having small amp. non-linearity 179 408 99 General purpose on A12 and later for audio devices having small amp. non-linearity Parameters of this module: - - - - 179 520 94, 93, ... , 87 for LDAC BT earphones and DAC's under $30 both having large amp. non-linearity External examples: - - - - 100 29 (91) 109 AK4493 (Sharp roll-off N-fold over-sampling) 150 42 (91) 109 AK4191EQ (Sharp roll-off N-fold over-sampling) 120 35 (97) 110 ES9038PRO (Fast roll-off N-fold over-sampling) vary 50 ~ 118 34 96 (398) ES9039PRO (Fast roll-off N-fold over-sampling) 110 40 (96) 109 CX43131 (Fast roll-off N-fold over-sampling) 98 130 98.5 MacOS Leopard (guess) 159 240 99 iZotope, No-Alias (guess) 100 64 99 SoX HQ linear phase (guess) 170 520 99 SoX VHQ linear phase (guess) - % in "Cut-off" and "Stop band" (starting from) fields means the proportion to the Nyquist frefuency.
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Appendix B. Characteristics of Re-sampling Parameters :
Category Background opaqueness (aliasing noise) Pre-echo and ringing Mellowness (intermodulation) Memo DAC light heavy heavy AK4491EQ Sharp roll-off DAC medium medium light ES9039PRO Fast roll-off Mastering tool slight slight light iZotope, No Alias (guess) Audio misc. settings almost none almost none light for general purpose Audio misc. settings very slight very slight medium for low performance devices Audio misc. settings slight almost none almost none for old devices This module almost none almost none very slight for LDAC BT earphones and DAC's under $30
- I am not responsible for any damage that may occur to your device, so it is your own choice whether to attempt this module or not.