Author Topic: Resampler quality  (Read 639 times)

ikonomov

  • Posts: 2
Resampler quality
« on: 28 May '22 - 04:30 »
Hi, I'm new here and with my limited search I haven't been able to find enough information, so I thought I would give it a try here in the forum.  For a bit of convenience for my particular setup and after reading some info about possible benefits of upsampling I've recently decided to upsample the output of the music player that I use, MusicBee, which uses BASS as its sound engine.  According to the developer the player is configured to use the highest quality resampling, which according to the http://www.un4seen.com/doc/#bass/BASS_CONFIG_SRC.html should be 4 = 64 point sinc interpolation.  I could not find any information about the type of filter being used and any testing of the quality of the resampling.  Has anybody done any testing of the quality of the resampler and maybe a comparison to something like SoX resampler or the default resampler of Windows 10?

Thank you!

Ian @ un4seen

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  • Posts: 24732
Re: Resampler quality
« Reply #1 on: 30 May '22 - 14:04 »
BASS uses a windowed-sinc filter. You can find information on that here:

   https://www.dspguide.com/ch16/1.htm

I haven't compared with other software myself, but from the test results on the http://src.infinitewave.ca/ website, the "iZotope RX 8.1 (Default)" graphs look pretty close to BASS with BASS_CONFIG_SRC=4. As in those graphs, BASS will let some (inaudible) high-frequency aliasing through to avoid attenuation in the audible range. The extent of that is determined by the transition band width, which the BASS_CONFIG_SRC setting controls (higher setting = narrower band). Higher settings (up to 6 = 256 points) are available through the BASSmix add-on if needed.

ikonomov

  • Posts: 2
Re: Resampler quality
« Reply #2 on: 31 May '22 - 21:43 »
Thank you Ian!

Hanuman

  • Posts: 89
Re: Resampler quality
« Reply #3 on: 1 Jun '22 - 20:10 »
Wow thanks changing this setting does greatly improve quality!

Any other hidden settings that can improve quality? (pitch-shifting from 440hz to 432hz)

Ian @ un4seen

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  • Posts: 24732
Re: Resampler quality
« Reply #4 on: 2 Jun '22 - 13:09 »
BASS_CONFIG_SRC/BASS_ATTRIB_SRC is the only setting in BASS that affects sample rate conversion quality. Another way to improve quality in general is to use the BASS_SAMPLE_FLOAT flag, which will allow you to decode/play 24-bit files in full quality and also improve DSP/FX processing. From the mention of pitch-shifting, it sounds like you're using the BASS_FX add-on's tempo processing? If so, you could also try experimenting with its settings (see the "Tuning the option attributes parameters" page in the BASS_FX docs).

Hanuman

  • Posts: 89
Re: Resampler quality
« Reply #5 on: 4 Jun '22 - 01:52 »
Actually I found yet another way to improve quality: opening the stream with BASS_SAMPLE_FLOAT

oups you said it already. No post DELETE button ?