“AirPlay streams at 16-bit, 44,100 kHz.,” Kirk McElhearn explains for Kirkville.
“However… AirPlay streams music in Apple Lossless format. What this means is that no matter what format your music is in, it gets converted by OS X – not by iTunes – to Apple Lossless, to ensure the highest quality,” McElhearn reports. “So lossless files will be streamed as lossless, as will AAC or MP3 files.”
“High-resolution files will be downsampled to 16/44.1,” McElhearn reports. “Interestingly, the Apple TV outputs audio in 48 kHZ, most likely because this is 48 kHz is the standard for movie and TV audio. Movies sold by the iTunes Store contain audio at 48 kHz, but only at 160 kbps.”
Read more in the full article here.
I’m not sure this is really right. Bandwidth usage on the LAN during streaming seems to say something else…
I just checked myself and it’s definitely sending ALAC, or at least bit rates to be expected with with ALAC. I’m verifying this by monitoring both the data rate from my sending Mac and the data rate from my receiving Mac.
What bandwidth usage are you getting on your LAN? Is it lower or higher than what should be expected with ALAC (~700 to ~1000kbps)?
I haven’t checked in a while, but the last time I did check, I know for certain that it WAS compressing my uncompressed AIFF files… While Apple Lossless is probably pretty good, with disc space so cheap, why bother?
As much as Steve Jobs loved music, you’d think he’d have insisted on a much better sounding system. I’m not even sure the iTunes doesn’t down convert my uncompressed audio files before it sends them to the D to A converter for me to listen to…. The same uncompressed files do seem to sound better when played thru other media players on the same sound system.
“I haven’t checked in a while, but the last time I did check, I know for certain that it WAS compressing my uncompressed AIFF files”
If that’s what you meant by saying the article wasn’t really right, then no, the article is correct.
What you’d be finding is that an AIFF file would require 1411kbps with no compression. If losslessly compressed as ALAC it would require 40-60% of that. That’s assuming it’s 16-bit 44.1Khz (CD quality), at 16-bit 48Khz, it’s 1536kbps uncompressed.
So if your router was showing 40-60% of what the AIFF should’ve transferred at, then you’ve demonstrated that the article is correct, it’s being converted to ALAC.
“While Apple Lossless is probably pretty good, with disc space so cheap, why bother?”
It has nothing to do with disk space. The files aren’t being compressed in iTunes, nor saved/replaced on your computer. They’re being transcoded on the fly by OS X and being sent over the network. The advantage of doing this is that you’re only using 40-60% of the network bandwidth that you’d otherwise be using. While most LANs can easily handle more than 1.5mbps, you’d be surprised at how a distant WiFi connection swamped with other traffic can interfere with this, so reducing the bandwidth needed can really help.
“Apple Lossless is probably pretty good”
It’s not “pretty good”, it’s lossless, as in without loss. Not only can’t you tell the difference from listening to an AIFF and a ALAC transcoded from it, but you can’t see the difference either.
Try this experiment. Take an AIFF and transcode it into an ALAC. Import them into a sound editor with a graphic time line. Inverse one of the tracks and then merge them. You’ll see that they cancel each other out.
Think of it this way, it’s like when you take a text document and zip compress it. It’s smaller than the original, but when unzipped, it’s the same size and contains the same text 100%.
As much as Steve Jobs loved music, you’d think he’d have insisted on a much better sounding system
Actually this is the attention to detail that does improve the sound. By compressing into a lossless format, less data may be lost due to bad connectivity thus resulting in at worst the same quality as if it was uncrompressed and possibly better quality and reliability if there are network issues.
“I’m not even sure the iTunes doesn’t down convert my uncompressed audio files before it sends them to the D to A converter for me to listen to”
It doesn’t. There would be no sense in that.
Too bad Apple has a LONG way to go to catch up with Emotiva
(they even have a professional looking spokesman….)
😉
I love it! I want one!