Functioning Replay Gain on Samsung Galaxy A33

[Hendrik_Simoens]

Hello,

For years I have been using the Replay Gain functionality now. But I was not totally convinced of the correct functioning of it. So finally I did a test.

So:

• I created a sequence of 8 short 1000 Hz audio pieces, each 30 seconds long.
• The first one had an amplitude of 0 dBFS (dB Full Scale; 0 being the maximum sinus that can be produced without distortion)
• The following ones all had diminishing amplites: -6 dBFS, -12 dBFS, etc
• So I played this series of audio pieces with my Samsung Galaxy A33.
  Note: the A33 was connected via Bluetooth to my Yamaha CD-NT670 and I measured (using an oscilloscope) the analog output of this Yamaha device.
• And I played this series once without Replay Gain working and once with Replay Gain working.

The result of this test is shown in the table below. See also the Excel I added.

Level    replaygain_    Maximum level A33    
             track_gain    Without RG    With RG
(dBFS)    dB                   (Vtt)            (Vtt)
  0         -20                     2,7              1,7
-6         -14                      1,3              1,7
-12         -8                      0,65           1,7
-18         -2                      0,34           1,7
-24        +4                      0,18           0,43
-30       +10                     0,09          0,43
-36       +16                     0,045        0,1
-42       +22                    0,02           0,05

Let me give some explanation about this table:

• The first column is obviously the amplitude of the audio piece in dBFS
• The second column shows the value of tag "replaygain_track_gain"
  Note: this had been calculated by my audio processing software on my PC and added as metadata in this tag. Your player uses this value if Replay Gain is set to on.
• The third column shows the resulting amplitudes in Vtt (Volt top top) at the output of my Yamaha when Replay Gain is off.
  The values nicely show a halving of the value for each audio piece, which perfectly corresponds to a 6 dB decrease of the amplitude
• The fourth column shows the same resulting amplitudes in Vtt when Replay Gain is on.
  You see that the first four audio pieces result in the same Vtt-value at the output, meaning that the Replay Gain functionality is functioning properly. Remark that the values of the tag "replaygain_track_gain" for this four audio pieces, all are negative (meaning tot some volume reduction should be applied).
  However, the next two audio pieces show a resulting Vtt-value at the output of 0,43 Vtt, about 4 times smaller than the previous ones. Meaning a very audible amplitude reduction of 12 dB. In the ideal (or normal) case, the output should have stayed at the same level of 1,7 Vtt.
  The following two audio pieces show even lower output values - probably my A33 is no longer able to apply enough gain to the signal.

BUT, it is the sudden drop of 12 dB that is strange to me, certainly when it happens exactly at the point where the  "replaygain_track_gain"-tag value turns from negative to positive.

Can you give me an explanation of this phenomen?

Kind greetings,

Hendrik Simoens

Functioning Replay Gain on Samsung Galaxy A33.xlsx

[Fitzian]

Was your RG setting in Poweramp "apply gain" or "apply gain / prevent clipping according to peak" ? I'd be curious to see how it affects your real world tests, here.

Edited September 1, 2023 by Fitzian

[Hendrik_Simoens]

"apply gain / prevent clipping according to peak"

Which also was clearly to see on my oscilloscope, since I didn't see any clipped sinus-shapes 🙂

[Hendrik_Simoens]

Hello,

 

I made two other measurements:

1. I used "apply gain" instead of "apply gain / prevent clipping according to peak". As I expected, this gave no difference in the results.
2. Then I reduced the setting of "Replay Gain Preamp" from its maximum 16 dB to the standard 0 dB.
   Note: I used this 16 dB gain setting in order to have a "normal" volume in my headphone.
   But now we have a quite different result! The level after the Replay Gain correction is much lower (16 dB which is normal) but it stays at the same level for signal levels going down from 0 dBFS up to -42 dB (the "green" range of signal levels giving a correct leveling has augmented with 24 dB!). This is very good. The drawback I have is that I have to go set the output volume to its maximum in order to have a good volume in my headphone.
   • In column F I show the gain between the output level with Replay Gain correction and the level without. You see that it goes from around -20 dB tot around +23 dB. Probably that is the gain range my A33 or the app is capable of applying (in particar positive Gain)
   • In column G is show the level in dBLUFS the system is aiming at (2,7 Vtt being 0 dBLUFS; @ 1000 Hz dBFS and dBLUFS have equal values). You see that the aim is around -20 dBLUFS. This corresponds quite well to the aim I have put in (-23 dBLUFS) for the calculation of the Replain Gain.

Final conclusion: although I would have preferred to have a higher possible output volume, the standard "Replay Gain Preamp"-setting of 0 dB, works alright for me.

Kind greetings,

Hendrik

Functioning Replay Gain on Samsung Galaxy A33.xlsx

[andrewilley]

There are limits as to how much RG boost/reduction is allowed to be applied. I had assumed that limit did not include the preamp setting too, but perhaps it does? 

Andre

[Hendrik_Simoens]

Dear André,

I also had assumed that the preamp-setting would not influence the RG-range! But unfortunately, it does.