DS Bit Rate Question


#1

Hi all,

I just upgraded from my PWD to a DS today. Wow, right out of the box with just Apple TV… phenomenal.

Anyways, I’m running an Apple TV through optical for the short-term right now and its doing something a bit strange. When I play a track, it starts out as 16 bit for a second or so, then turns to 24 bit. It’s weird because I believe Apple TV only outputs at 16bit. Either way, no matter the bit rate, it starts at 16 bit for a second, then goes to 24.

I can’t say I’m concerned if it is just a weird Apple TV thing. I just want to make sure its working OK.

As always, thanks for your expertise everyone!

John


#2

The DS is reporting what’s actually coming over the wire. A report of 24 means that the one of the least significant 4 bits in the 24 bit data is non-zero at least once every time unit (10ms?, I don’t remember at the moment.) Do you have some form of volume leveling or DSP going on? (I don’t have any experience with Apple TV so I don’t know what’s normal there.)


#3

Streaming MP3 perhaps?


#4

I have seen this on the optical input on occasion as well when the source is a DirecTV receiver. I treat it as an anomaly; I do not think the receiver is ever sending a legitimate 24 bit stream.


#5

Thanks all!

I did a bit more snooping around, and I found an “audio output” setting… you can choose either 16bit or “auto” which results in 24. I guess “auto” is doing some sort of processing.

In my case, I’m streaming either AIFF or ALAC… but I’m not sure what actually comes out of the Apple TV. I’ve been told it is the same file type that is on iTunes, but I’m not sure how to test it.

FYI, it only outputs at 48kHz.

I’m looking forward to installing my bridge from my PWD when I get a bit of time, but man the Apple TV is easy! And, the DS with the ATV is an amazing improvement compared to the PWD with the ATV. Nice job team!

John


#6

AirPlay via an AirPort Express gives you bit-perfect 44.1kHz 16-bit transfers if you’re playing CD rips.

AirPlay via an Apple TV takes that 44.1kHz 16-bit stream and then upsamples it to 48kHz 24-bit. It’s not the ideal thing for audiophiles, but the DS makes it sound great anyway.


#7

Thanks dvorak!

That upsampling is definitely not ideal. I’m all hardwired right now, but I think Airport Express can send wired optical too.

Interesting alternative solution until I get my bridge (with hopefully a soon-to -be-released version II) up and running!

John