View Full Version : which format is actually transmitted?

2007-10-19, 12:13
Hi there,

I am wondering which format sound is actually transmitted from the SlimServer to the SqueezeBox. Is it RAW PCM? WAV? Some compressed format?

And which bitrate/sampling?

I thought that a PCM 16bit/44.1KHz signal was sent to the SqueezeBox, which would only DAC it. But, noticed that SlimServer uses the flac command-line tool for reading my .wav files.

Can anyone clear this out?



Mark Lanctot
2007-10-19, 12:32
If the format is listed as "built in" and enabled in Server Settings - File Types, it's sent as that file and decoded in the SB.

SS never sends a PCM signal, a router wouldn't know what to do with it. It's always one of the built-in formats, or something that's transcoded to one of the built-in formats.

2007-10-19, 12:49
If the format is listed as "built in" and enabled in Server Settings - File Types, it's sent as that file and decoded in the SB.

OK, I see a WAV can have 3 "stream formats": FLAC, MP3 and WAV. Both streams via FLAC (flac decoder) and WAV (built-in) are enabled. So, which one is actually used?
Can I control this? If it is sent as WAV, what is the flac command-line tool doing in my system?

What is done to the stream to get to digital-out (coax) after it gets to the SB ?

Thanks for the quick answer,


2007-10-19, 12:53
Pointers with more information about these issues are welcome.

Thanks. G

Mark Lanctot
2007-10-19, 12:57
If you keep WAV - WAV built-in checked, FLAC - FLAC built-in checked and MP3-MP3 built-in checked, it should send WAV as WAV, FLAC as FLAC and MP3 as MP3 and the SB will decode to PCM.

If you have WAV - WAV unchecked and WAV - FLAC checked, it will transcode to FLAC and you should have a FLAC process running on your system.

If this isn't the case, I don't know what the problem is - but it isn't a problem anyway beside CPU usage as FLAC and WAV are identical (and no comment from the peanut gallery!)

But I believe I see what's going on now. If you have WAV - FLAC checked, SS will prefer this over WAV - WAV in order to save bandwidth. Uncheck WAV - FLAC if you want WAV sent as WAV.

2007-10-19, 17:45
The options in the server specify what is allowed, for example in your case it's saying that WAV->FLAC and FLAC->FLAC are allowed. To decide between the two it looks at the type of player in use and decides based on it's preference. An SB3 prefers FLAC first, then WAV, then MP3. So your WAVs will be encoded to FLAC on the server and then decoded back to PCM on the SB3. This is good because it saves bandwidth on the network which makes the wireless streaming more reliable. If you don't want that to happen (for example if you want to save CPU on the server) disable the WAV->FLAC option.