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True Peak detection and gain adjustment before DSD to PCM conversion

Posted: Mon Nov 09, 2020 11:52 am
by Timecode
It would be nice if we could have a firt pass with truepeak detection before to convert from DSD to PCM.

I've seen that dsd to flac encodings are often clipped. Probably because users don't check peaks before conversion and directly apply a +6dB gain in the SACD settings.

Actually DSD to PCM conversion is a manual process. Convert with 0dB gain, find the peak value with Dynamic Range analysis, manually adjust gain from 0 to +6 dB in the SACD settings to avoid clipping, then do the conversion with the right gain value.

Could be done automatically for each track or for a wall album, same philosophy as dynamic range detection.

A side note : is dynamic range detection using true peak or normal peak detection ? If it is normal peak then can be ok if detection sample frequency is more than 96 Khz.

I suppose that the SACD default sample rate is used during dynamic range detection. If it's the case, it would be better to always run first pass peak detection at DXD sample rate for true peak detection.

It has been demonstrated that true peak can be as high as +3dB compared to normal peak values for a 44.1 KHz signal. An interesting thing in DR detection would be to have the 2 values reported, peak and true peak.

As another side note, true peak overs are normally not a problem for DAC converters, if they are correctly designed with enough analog headroom (around 3 dB of headroom).

But true peak overs can probably induce small saturations when converting later to another format like MP3.

I think that this is important to always check for true peaks when converting heavily compressed audio material.

Re: True Peak detection and gain adjustment before DSD to PCM conversion

Posted: Wed Nov 11, 2020 10:10 am
by Timecode
Another option would be a true peak check during conversion, asking the user to stop the conversion process and change the SACD gain before converting again.

Would it be possible to add value from +7 to +10 dB ? Sometimes classical albums are quite low and need this amount of scaling.