Airport Express Converts to ALAC?

[webby]

Is it true that the Airport Express converts what's streamed to it to ALAC? If so, what effect does this have on ALAC files streamed to it?

 

If this is true, it kinda defeats my object of ripping to AIFF, doesn't it? Other than keeping that as the 'master copy'.

 

[Audio_ELF]

Yes. Everything sent to Airport Express is converted to ALAC.

 

Files already in ALAC format have no conversion applied AFAIK. AAC, MP3, AIFF, etc are all converted before being sent over the ether.

 

Eloise

 

[webby]

I find this strange and I'm still not sure it's true. Maybe for the analogue output yes, but if it were using the digital output would it not output the data as is (pass it through untouched)?

 

My idea was to rip everything to AIFF and play back from them. I could convert to AAC 256 any tracks I want on my iPod from those AIFF files. However, if the Express is going to convert to ALAC on the fly then ripping to AIFF seems pointless (in this setup).

 

What do you think?

 

[Audio_ELF]

The file format (ALAC, AIFF, etc) is separate to the digital or analogue output issue.

 

ALAC is used as it reduces the amount of data being sent across the network and reduces the likely hood or dropouts and hicups due to data not getting to the AE (Airport Express) in time.

 

As for ripping, if you decide to rip to ALAC format, you can later convert to AIFF without any loss of quality. It's analagous to using a ZIP file - you're never worried with that you're going to loose letters in a document. Some people say they notice a difference in quality playing back ALAC vs AIFF but this is a debatable issue.

 

Hope to have put your mind at rest.

Eloise

 

 

 

[webby]

"ALAC is used as it reduces the amount of data being sent across the network and reduces the likely hood or dropouts and hicups due to data not getting to the AE (Airport Express) in time."

 

Now I'm confused! So, it gets converted BEFORE getting to the AE?

 

Thanks for clearing up the format query.

 

[Audio_ELF]

iTunes converts to ALAC then sends it via Ethernet to the Airport Express. This is all transparent to the user and does (should) not affect the end sound quality.

 

Eloise

 

[cfmsp]

 

 

"iTunes converts to ALAC then sends it via Ethernet to the Airport Express."

 

Eloise, I think you meant to say that iTunes converts to ALAC and then send it via Airtunes (i.e. wirelessly) to the Airport Express.

 

FWIW, the Apple TV can also serve as an Airtunes client - just like the AE - and it apparently has higher quality chips and whatnot.

 

The aspect of the conversion of AIFF to ALAC that is unknown to me is whether or not AIFF files are re-converted back to AIFF (by the Airtunes client) for playback?

 

 

 

 

[Audio_ELF]

Airtunes is a protocol which runs over Ethernet either wired or wirelessly. So think we're saying the same thing really.

 

At the Airport Express (or AppleTV) the data is uncompressed to LPCM format the same as if your Mac sent an AIFF file straight out it's optical port. The data getting to your DAC is the same in both cases.

 

Hope my explanation makes sense.

Eloise

 

[webby]

So, basically, (and this is the essence of my original question, even if I didn't word it well) whatever quality of audio you/I send to the AE, that is what comes out at the other end?

 

So, a 128kbs MP3 is converted to ALAC as this is the protocol that the AE works with. The AE then 'uncompresses' that back to a 128kbs MP3 audio file (in analogue form).

 

Ergo, an uncompressed AIFF file is converted (compressed) to ALAC and sent to the AE. The AE then 'uncompresses' that back to an AIFF quality audio file and 'voila', CD quality playback.

 

If I send it ALAC though, does it still 'uncompress' to, well, the original uncompressed file?

 

Sorry about these questions, but I'm getting there!

 

 

 

[Audio_ELF]

In essence yes that's right.

 

An AIFF file is converted to ALAC for transmission then converted by the AE to PCM data identical to the original CD data (assuming CD - 16/44.1 - quality)

 

An AAC file is converted to ALAC for transmission and is also converted by the AE to PCM however in original creating the AAC file quality will have been lost and this loss cannot be recovered.

 

An ALAC file is sent (without change) to the AE and is converted back to PCM data identical to the original data on the CD.

 

Edit/addition: Yes ... The quality that comes out of an Airport Express is the same as the quality of the file you send to it. It is more complicated than that, but really that's all you need to know.

 

[webby]

Brilliant!

 

Finally I understand, plus it's kinda the answer I was hoping for. I think the info I had before I came here was a little vague as was my understanding of it. All I knew was that the AE converted everything to ALAC, which as I now know, doesn't really explain everything that's going on.

 

My knowledge of ALAC not being that good didn't help either.

 

Thank you.

 

[iamimdoc]

There are several products that allow other software programs ("not I-tunes") to stream to an AE, eg. Rogue Amoeba's and Eric Milles' Remote Speaker Output.

 

I use mainly FLAC files and things work without a hiccough.

 

WAV and AIFF files work also.

 

Iam curious: Does anyone think any ALAC conversions are in play in this setup?

 

[cfmsp]

 

 

+1 on Airfoil. I'm a happy customer despite the rather high price for what it is.

 

 

AFAIK, Rogue Amoeba re-routes non-iTunes audio to Airtunes, which would then do a conversion to ALAC.

 

clay