Doom9's Forum - View Single Post - Peak audio level vs average which should be higher?

hello_hello · 4th October 2018, 22:24

datauser,
I had a look at the Sound Normalizer program and the way it does things seems a bit odd. I scanned an MP3 with foobar2000 and then converted it to flac while adjusting the volume to ReplayGain's 89dB. I then scanned the flac file to determine it was correct, and the track gain shown was 0dB (which means it's exactly 89dB), and the peak value was 0.562433, which is basically a percentage and works out to -4.99858 dB below maximum (fb2k shows -5.0dB).

When I scanned with Sound Normalizer it showed an average volume of 88dB for the left channel and 89.6dB for the right channel, so I guess that's about right. It says I can increase the volume to 93.0dB for the left and 96dB for the right, for maximum volume without clipping, which is probably also correct.
For the peak levels though, it showed 85.3dB and 83.9dB.

When I switched to displaying a percentage, the average levels were 98.8% and 100.7% which makes sense for average values of 88dB and 89.6dB, assuming 89dB=100%. For the peak levels it shows 56% for the left channel and 48% for the right, which is in line with foobar2000's 0.562433 (56.24%)

So I think it's doing something retarded like changing the meaning of 89dB when displaying peak values, and the volumes of 85.3dB and 83.9dB as peak levels are relative to that. I can't quite get my head around what it's relative to though, as it shows the maximum peak volume for each channel as 90.3dB. ReplayGain's 89dB is confusing enough as it is without making it worse.

If you're interested, I posted some info on how to adjust the volume using foobar2000 and ReplayGain here. fb2k uses the newer R128 scanning algorithm, even though it still refers to everything in ReplayGain-speak, so it's results can sometimes be a little different to MP3Gain (the newer scanner is more accurate). It'll also adjust the volume of MP3s and AAC files losslessly as MP3Gain does, only it'll do so when the audio is inside a container such as MP4 or MKV. It doesn't mind if there's also video. It doesn't display the info in the same user friendly manner as MP3Gain though, but it's easy enough to adjust the volume when converting and scan the output files to check the peaks, or check the peak values after they've been adjusted losslessly.

Oh... and fb2k doesn't have an option for peak normalising as such, but when converting it can be achieved by selecting the "apply tack gain and prevent clipping according to the peak" option in the converter's ReplayGain section and setting the "with replay gain" pre-amp to +20dB. That'll increase the volume to 20dB above ReplayGain's 89dB target volume, or to the maximum volume without clipping, whichever comes first. I think the same applies when adjusting losslessly. You'd increase the target volume in preferences to something above 89dB and also check the "prevent clipping" option.

4th October 2018, 22:24	#4 \| Link
hello_hello Registered User Join Date: Mar 2011 Posts: 4,829	datauser, I had a look at the Sound Normalizer program and the way it does things seems a bit odd. I scanned an MP3 with foobar2000 and then converted it to flac while adjusting the volume to ReplayGain's 89dB. I then scanned the flac file to determine it was correct, and the track gain shown was 0dB (which means it's exactly 89dB), and the peak value was 0.562433, which is basically a percentage and works out to -4.99858 dB below maximum (fb2k shows -5.0dB). When I scanned with Sound Normalizer it showed an average volume of 88dB for the left channel and 89.6dB for the right channel, so I guess that's about right. It says I can increase the volume to 93.0dB for the left and 96dB for the right, for maximum volume without clipping, which is probably also correct. For the peak levels though, it showed 85.3dB and 83.9dB. When I switched to displaying a percentage, the average levels were 98.8% and 100.7% which makes sense for average values of 88dB and 89.6dB, assuming 89dB=100%. For the peak levels it shows 56% for the left channel and 48% for the right, which is in line with foobar2000's 0.562433 (56.24%) So I think it's doing something retarded like changing the meaning of 89dB when displaying peak values, and the volumes of 85.3dB and 83.9dB as peak levels are relative to that. I can't quite get my head around what it's relative to though, as it shows the maximum peak volume for each channel as 90.3dB. ReplayGain's 89dB is confusing enough as it is without making it worse. If you're interested, I posted some info on how to adjust the volume using foobar2000 and ReplayGain here. fb2k uses the newer R128 scanning algorithm, even though it still refers to everything in ReplayGain-speak, so it's results can sometimes be a little different to MP3Gain (the newer scanner is more accurate). It'll also adjust the volume of MP3s and AAC files losslessly as MP3Gain does, only it'll do so when the audio is inside a container such as MP4 or MKV. It doesn't mind if there's also video. It doesn't display the info in the same user friendly manner as MP3Gain though, but it's easy enough to adjust the volume when converting and scan the output files to check the peaks, or check the peak values after they've been adjusted losslessly. Oh... and fb2k doesn't have an option for peak normalising as such, but when converting it can be achieved by selecting the "apply tack gain and prevent clipping according to the peak" option in the converter's ReplayGain section and setting the "with replay gain" pre-amp to +20dB. That'll increase the volume to 20dB above ReplayGain's 89dB target volume, or to the maximum volume without clipping, whichever comes first. I think the same applies when adjusting losslessly. You'd increase the target volume in preferences to something above 89dB and also check the "prevent clipping" option. Last edited by hello_hello; 4th October 2018 at 22:51.