Quote:
Originally Posted by asc28
I'll convert to floating-point PCM to apply the volume change, and then feed the floating-point directly to Nero AAC encoder. Hopefully, if I understand these concepts correctly, this should not result in much quality loss, had I just encoded an originally correct-volume PCM to AAC.
|
I actually might instead change the volume by applying gain on the AAC post-encode. I believe this would be a lossless process if the gain can be applied the same way mp3gain does it (by modifying the frame headers). Will eac3to do it this way (change volume losslessly by modifying ADTS frame headers on the AAC) if I do: eac3to input.aac output.aac -Xdb?
[edit] Also here are some tests I did w/ the latest WaveGain:
Quote:
wavegain sin51.C.wav sin71.C.wav sin51.LFE.wav sin71.LFE.wav sin51.L.wav sin71.L.wav sin51.R.wav sin71.R.wav
Analyzing...
Gain | Peak | Scale | New Peak |Left DC|Right DC| Track
| | | |Offset | Offset |
--------------------------------------------------------------
-1.16 dB | 32767 | 0.87 | 28671 | 0 | 0 | sin51.C.wav
+2.19 dB | 21538 | 1.29 | 27715 | 0 | 0 | sin71.C.wav
-0.00 dB | 32767 | 1.00 | 32766 | 0 | 0 | sin51.LFE.wav
+3.64 dB | 21538 | 1.52 | 32765 | 0 | 0 | sin71.LFE.wav
+0.15 dB | 32209 | 1.02 | 32766 | 0 | 0 | sin51.L.wav
+3.64 dB | 21538 | 1.52 | 32765 | 0 | 0 | sin71.L.wav
+0.02 dB | 32681 | 1.00 | 32766 | 0 | 0 | sin51.R.wav
+3.64 dB | 21538 | 1.52 | 32765 | 0 | 0 | sin71.R.wav
WaveGain Processing completed normally
|
Looks like the volume difference is not exactly the same for every channel (varies from 3.35 to 3.64), though this might be explained by how the extra 2 channels are mapped / DTS compression.