Decibel and Airfoil (again)

[pl_svn]

... always thought the output of a music player was just digital data and transmitted as such over wi-fi but... got an answer, from Rogue Amoeba, that makes me think Airfoil "re-encodes" Decibel's output into ALAC (then decoded by the AirportExpress). this is what RA told me:

"Airfoil transmits audio based on the AirPlay audio protocol, which specifies a 16-bit stereo, Apple Lossless stream at 44.1 kHz. So, it's not FLAC, but it is lossless."


my doubt is: so... using Airfoil, I'm not sending (to my DAC) Decibel's bit perfect output? :-/
(in Decibel I'm playing FLAC 16/44.1 files)

and... yes: tried asking RA if Airfoil re-encodes before transmitting, but got no further answer :-/

[Fuga]

Sure would explain the glitches, whether using Decibel or Cog or whatever. Now FLAC on Swinsian over wireless is flawless as it leverages Airplay.

[sbooth]

I can't say definitively, but given what you've posted it does sound like Airfoil re-encodes the audio it is sending.

[pl_svn]

Sure would explain the glitches, whether using Decibel or Cog or whatever. Now FLAC on Swinsian over wireless is flawless as it leverages Airplay.

... ok, further answer from Rogue Amoeba:

"Airfoil performs any necessary adjustments to the audio data so the stream will be properly recognized by AirPlay-compatible devices on your network, which will only handle it in that 16-bit stereo Apple Lossless format."

so... no: whatever you send to an Airport Express is re-encoded to Apple Lossless, the only file format the AE knows about and accepts :-/


also got, this afternoon, a session with "the computer audio guy" at my hi-fi dealer and found that... whatever kind of network (wired or wireless) is only good to transfer "raw data" to a dedicated network player (that has to be physically connected to the amplifier). if, instead, you stream "decoded audio"... it always gets manipulated along the way

I mean... all this is for *extreme purists* only ;-p

[mattn]

Actually the ALAC claim sounds optimistic to me. My impression was that whatever arrived via wireless to e.g. an Airport Express was lossy-compressed. Certainly my Airport Express puts out very disappointing sound. That might be because it's lossy-compressed or because the D/A conversion inside the Airport Express sucks. Suffice it to say that in my experience wireless and audiophile are opposites. However, wireless is sure convenient. Everything is a tradeoff.

[Fuga]

All I know is FLAC through Swinsian has no glitches. FLAC through any other player then Airfoil will have glitches. So Swinsian must converting to ALAC before sending whereas Decibel/Audirvana/Cog/whatever starts to send FLAC, and keeps doing it, and Airfoil says "Oh, crap! Can't you wait a sec while I do my thing?!"

Hmmmm, maybe Airfoil needs to have a much larger "memory cache" or some such so it could grab enough from the player and do its thing in large enough chunks so as not to have glitches. I apologize for the non-tech-speak.

More, hmmmmm. I have the same amount of glitches on the same tunes even when they are already in ALAC if I'm using Airfoil with Decibel/Audirvana/Cog/whatever. Me thinks the encode/format is only part of the problem.

[pl_svn]

Me thinks the encode/format is only part of the problem.

re the "glitches issue"... me thinks (and believe I already told you) there's too much data traveling back and forth on your network :-p
try connecting your hd directly via USB and use the wi-fi network only to stream from the player, not also to, at the same time, load files from an "AirDisk"
(also: when the HD goes in sleep mode, it takes a very long time to wake-up if connected wirelessly)

with Decibel, music files (FLAC) on a USB HD, and Airfoil streaming to an AE I've never had a single hiccup. not even when Time Machine kicks-in

[Fuga]

Yes, you've told me but I must say again that all is fine when Airfoil is not in the sequence. FLAC on Swinsian is flawless.