WAV vs FLAC/WV render - different output (with fx, resampling) (FIXED)

inoto · 02-13-2022, 07:16 AM

If I render or use the batch converter I get slightly different audio depending on which of these formats I select for the output.
This happens at least if FX or resampling is used.

Example repro:
1. Open the batch converter.
2. Load a file (I tried with WAV and FLAC).
3. Keep the source sample rate and source channels.
4. Add some FX, for example ReaEQ with some boost/cut. You have to change some values, not just load the plugin.
5. Output format: WAV 24 bit, then repeat with FLAC or WavPack 24 bit.

Alternative repro: no FX, but just change the sample rate (I tried with r8brain and sinc 786).

Result:
The WAV and FLAC/WV files are not bit identical. Whereas two WAVs or two FLACs or a FLAC and a WV file are bit identical and null to -inf.
(Once it happened that two WAVs didn't null either, but that's a different problem that I can't reproduce now.)

Reaper 6.47 64bit, Windows 10

I noticed this when doing some resampling tests. The WAV files looked a bit cleaner at very low levels.
What's going on? Some additional truncation for FLAC/WavPack?

Justin · 02-14-2022, 09:48 PM

There are some very, very slight rounding differences (in the LSB) between flac/wavpack and .wav, when writing 24-bit, and when converting from content which is >24 bit (e.g. resampled or FX). Also, if dithering is enabled, they produce the same result (the dither quantizes them to 24-bit).

Having said that, we'll make them consistent for the next +dev builds (and a release eventually).

inoto · 03-03-2022, 01:55 AM

Thanks! I see that it's not fixed in the latest pre-release, even though it was fixed earlier (in dev0215).
Maybe this is according to plan and it's not really an urgent matter... I just want to make sure it wasn't forgotten.

02-13-2022, 07:16 AM	#1
inoto Human being with feelings Join Date: Nov 2021 Posts: 47	WAV vs FLAC/WV render - different output (with fx, resampling) (FIXED) If I render or use the batch converter I get slightly different audio depending on which of these formats I select for the output. This happens at least if FX or resampling is used. Example repro: 1. Open the batch converter. 2. Load a file (I tried with WAV and FLAC). 3. Keep the source sample rate and source channels. 4. Add some FX, for example ReaEQ with some boost/cut. You have to change some values, not just load the plugin. 5. Output format: WAV 24 bit, then repeat with FLAC or WavPack 24 bit. Alternative repro: no FX, but just change the sample rate (I tried with r8brain and sinc 786). Result: The WAV and FLAC/WV files are not bit identical. Whereas two WAVs or two FLACs or a FLAC and a WV file are bit identical and null to -inf. (Once it happened that two WAVs didn't null either, but that's a different problem that I can't reproduce now.) Reaper 6.47 64bit, Windows 10 I noticed this when doing some resampling tests. The WAV files looked a bit cleaner at very low levels. What's going on? Some additional truncation for FLAC/WavPack? Last edited by inoto; 02-13-2022 at 07:28 AM.

02-14-2022, 09:48 PM	#2
Justin Administrator Join Date: Jan 2005 Location: NYC Posts: 16,335	There are some very, very slight rounding differences (in the LSB) between flac/wavpack and .wav, when writing 24-bit, and when converting from content which is >24 bit (e.g. resampled or FX). Also, if dithering is enabled, they produce the same result (the dither quantizes them to 24-bit). Having said that, we'll make them consistent for the next +dev builds (and a release eventually). Last edited by Justin; 02-14-2022 at 10:14 PM.

03-03-2022, 01:55 AM	#3
inoto Human being with feelings Join Date: Nov 2021 Posts: 47	Thanks! I see that it's not fixed in the latest pre-release, even though it was fixed earlier (in dev0215). Maybe this is according to plan and it's not really an urgent matter... I just want to make sure it wasn't forgotten.