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Rockbox mail archiveSubject: Re: 16/24bit?Re: 16/24bit?
From: Rocker <rocker_at_shaw.ca>
Date: Wed, 13 Sep 2006 18:22:10 -0600 LOL! I love the research dude! I always thought that 2 inch tape is still the best! rocker ----- Original Message ----- From: "Jerry Van Baren" <gerald.vanbaren_at_smiths-aerospace.com> To: "Rockbox" <rockbox_at_cool.haxx.se> Sent: Wednesday, September 13, 2006 7:46 AM Subject: Re: 16/24bit? David Pedersen wrote: > Sorry, this migh be a silly question: > > I have approx. 200 MiniDiscs, filled with recordings. I now want to > transfer them into my Archos. The miniDiscs are mainly recorded with > 24bit technology. My soundCard on the computer only supports 16bit. Ok, > I know, that it is no problem to record the 24bit discs with my 16bit > soundcard, as I already have done so, in several cases; and then turn > the whole thing into MP3. But my question is: > Would I have any benefit of getting a 24bit soundcard for the > computer? Does the MP3 technology care for 24bit? And will the RB/Archos > give me better sound with the 24bits? > > David > Archos JBR v1, RB2.5 From an engineering point of view, 24 bits is entirely marketing hype for everything but professional audio equipment, typically with very high price tags (hundreds to thousands of dollars). Dynamic range (dB) = 20 * log10(2^n) Bits Signal range (dB) 16 96 17 102 18 108 19 114 20 120 21 126 22 132 23 138 24 144 In order to get 16 bits of useful resolution (i.e. 16 bits of signal) in your digital stream, your analog front end (e.g. opamps plus associated components such as resistors and capacitors) must have a combined noise floor of significantly better than 96 dB. You also need to look at the signal to noise quality of the A/D itself... the highest quality A/Ds typically have a S/N rating of around 120-126 dB (21-21 bits). This means a very high quality A/D with a high quality front end and an extremely high quality PCB (power supplies and layout is incredibly important) gets you 20-21 bits of real signal plus 3-4 bits of noise. We are talking close to heroic measures with proportional costs here. The above is _before_ compression is applied. So my answers to your questions are: Q: Would I have any benefit of getting a 24bit soundcard for the computer? A: No. Soundcards plugged into PCs don't have anywhere close to 24 bits of useful resolution, despite the marking hype. PCI board physical restrictions make proper board layout to achieve extremely high quality audio impossible or nearly so. I suspect many, perhaps most, PC sound cards struggle to achieve true 16 bits of signal to noise ratio. The inside of a PC is saturated with electrical noise! Q: Does the MP3 technology care for 24bit? A: More bits is always better, but you will be throwing away a lot of information in the lossy compression so the result is highly unlikely to be distinguishable between "24 bits" and (true) 16 bits. Q: And will the RB/Archos give me better sound with the 24bits? A: Definitely not. The Archos hardware is nowhere close to the very careful design that 16 requires and miles away from the heroic measures that 20 bits require. The Archos was designed to be small, inexpensive, and used in relatively high noise (not sound booth quality) environments. I suspect, based on discussion on this mail list and my own empirical listening experiences (but _not_ on actual measurements) that the Archos hardware is probably on the order of 14 bits of signal and 2 bits of noise. If you had a perfect 24 bit signal (say a computer generated synth sound), you still cannot get any better than the Archos output S/N (and that is ignoring the compression losses as well). Minidisk audio is compressed as well (ATRAC), meaning your "24 bits" isn't really. <http://en.wikipedia.org/wiki/Minidisk> Are you sorry you asked now? ;-) gvb Received on 2006-09-14 Page template was last modified "Tue Sep 7 00:00:02 2021" The Rockbox Crew -- Privacy Policy |