Support and General Use > Audio Playback, Database and Playlists
-24db Precut Sound Quality on Rockboxxed iPod?
Andhyka:
Exactly, "normalize" does not add any clarity/fidelity to existing audio signal. It just amplifies/maximizes to its maximum limit based on signal peaks.
The antonym to "normalize" is "compress", which I thought was done at Rockbox pre-cut feature. And then, I realized from your reply that it cut away the insignificant bits of audio signal, which if done at -24db pre-cut, can make the music sounds boring/dull/lifeless. :'(
Having a highly detailed headphone like MDR-SA5000, the difference between 0db pre-cut & -24db pre-cut is night and day. Also I believe that -24db pre-cut is performed before the audio signal enters Rockbox DSP, and is upsampled from 16bit to 32bit. So yeah, it's 4 bit short - 2^16=65536 vs. 2^12=4096 - and it's substantial.
Thanks for the feedbacks/replies. It really helps me improve my understanding on hi-fi.
Cheers.
Llorean:
You're still wrong. Compressing an audio signal as a method for reducing the loudness reduces its dynamic range. It is impossible not to. I don't know how I can make this more clear:
You cannot magically make a signal smaller and not lose some of it when working in digital.
If one foot were divided into 16 segments, and then you decided to shrink something down to use only 15/16 of that foot, and you have to use the same size segments still, you then only get to represent it with 15 segments, not 16 any more.
When you compress audio, you're still working with a pre-defined number of bits, so some data will be lost. It's that simple.
As well, in all honesty, a 24db cut at 16-bit vs 32-bit should result in the same number of final bits lost. You're still lowering the volume by the same amount, independent of whether the signal is represented by 16 bits or 32 bits. My example earlier was just that if you were losing 4 bits at 32-bit, those 4-bits would be equivalent to 2 at 16-bit. How much you lose should be in constant ratio, the only real advantage at 32-bit should be that as you have more resolution, is that you have to round less often for operations.
Andhyka:
Umm yeah you are right about that. Sigh, I wish the "compress" was done after 16-bit audio signal is upsampled to 32-bit. The whole notion on pre-cut seems to indicate loss of SQ.
I just wished Rockbox would upscale 16-bit signal to 32-bit signal, then compress it back with -24db.
Llorean:
You cannot magically *not* lose data.
If you scale to 32-bit, then compress, then decrease to 16-bit, it will be equivalent to compressing at 16-bit. Both lose data. Since this is the only operation you're doing (compression) converting to 32-bit is pointless: You can ensure that the rounding necessary is done in the same way during the compression if you really want to. Working in 32-bit reduces the loss of accuracy when you perform multiple operations because you have more resolution.
Febs:
--- Quote from: Andhyka on August 07, 2007, 11:32:04 PM ---Umm yeah you are right about that. Sigh, I wish the "compress" was done after 16-bit audio signal is upsampled to 32-bit. The whole notion on pre-cut seems to indicate loss of SQ.
I just wished Rockbox would upscale 16-bit signal to 32-bit signal, then compress it back with -24db.
--- End quote ---
Could you define how you're using the word "compress" here?
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version