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View Full Version : 24bit FLAC vs 3100 Kbps stream



Doermann
2008-08-08, 13:30
Im using the DUET (firmware 42 with SC 7.2 beta) and when i play 24bit FLAC with over 3100Kbps i have distortion and music is choppy.

I dont think it's my network since 24bit WAV with over 4600 Kbps play just fine.

Look more something like the DUET hardware is not fast enough to decompress 24bit FLAC over 3100Kbps in real time.

andyg
2008-08-08, 15:03
What's the sample rate? 24/44.1 or 48 shouldn't have a bitrate that high. Normal 24/96 files only have a bitrate of around 2300-2500k.

88.2k and 96k files on Receiver are also downsampled so that may also be what you are experiencing.

seanadams
2008-08-08, 15:35
88.2 and 96 KHZ are only supported on Transporter.

Doermann
2008-08-08, 15:59
24bit 96khz

Matt Wise
2008-08-08, 16:01
But you could buy a Transporter, and control it with your Squeezebox Controller.. :)

(and your receiver could be relegated to something more mundane, like someones bedroom or back yard or something.... )

Doermann
2008-08-08, 19:08
88.2 and 96 KHZ are only supported on Transporter.

Why for? ...

schiegl
2008-08-09, 01:18
Why for? ...

CPU (325MHz vs 250MHz). Search the product pages (or the forum)

Doermann
2008-08-09, 08:04
CPU (325MHz vs 250MHz). Search the product pages (or the forum)

Dont tell me +75mhz cost 1000$ more (DUET vs Transporter). I found this very bad that the new DUET cant read 24bit 96khz FLAC because lack of CPU power and much more because of only 75mhz.

:(

seanadams
2008-08-09, 08:34
There is a lot more to it than just CPU speed, although that is a major limiting factor in terms of the data rate that the device can decode. It is also a function of everything downstream from the CPU being designed for 88.2/96KHz playback. No, 75MHz more CPU speed does not cost $1000, but it does cost a few dollars per unit that we can not justify in our most inexpensive products.

Pumpa
2008-08-09, 12:57
Overclock with heatsink ? :)

Doermann
2008-08-10, 08:00
It is also a function of everything downstream from the CPU being designed for 88.2/96KHz playback..

What you mean by everything downstream exactly?

seanadams
2008-08-10, 12:52
What you mean by everything downstream exactly?

Besides the processor there is logic, oscillators, and the s/pdif and/or DAC outputs. So the system has to be designed from the start for 96KHz to work, and you may be surprised that doubling the data rate is a major design exercise, above and beyond throwing money at a faster CPU and higher speed grade grade parts. As an example Transporter does in hardware (programmable logic) some things that SB3 does in software, necessitating more logic, in order to offload some CPU time and IO load.

It's not just a marketing driven thing, but you really do have to be careful where you allocate BOM dollars. Although you could (correctly) observe that any _one_ of the features in the higher-end product could have been added to the lower-end product for $X, there is no more demand for 96KHz than there is for, say, a word clock input, so the only sane design choice is to put the features that everyone needs (or the features that are free to implement) in the lower-cost product, and then package all the more specialized features into a higher end product. Otherwise you'll never meet the price point for the high volume product in the first place, because all customers would be shouldering the cost of those features, whether they use them or not.

Doermann
2008-08-10, 22:13
Ok, thanks.

It's pretty much clear to me.

And for the 24bit 96Khz FLAC is the DUET playing them in that quality or there is a downgrade to 44Khz?

seanadams
2008-08-11, 07:05
Ok, thanks.

It's pretty much clear to me.

And for the 24bit 96Khz FLAC is the DUET playing them in that quality or there is a downgrade to 44Khz?

It drops every other sample, which is not correct down-sampling, so it's not playing them correctly at all. Personally I think that we should never have enabled this feature because of the confusion it causes, but there are a lot of people who would like their Squeezebox to play _something_ when it is synced with a TP and a 96KHz track comes up in the playlist.

Doermann
2008-08-11, 11:19
If i understand when a 24bit 96Khz FLAC play, the DUET read them as 44Khz and drop the rest. So the extra informations are not processed at all, right?

As a long time owner of Slimdevices SB3 (since it came out) and now the DUET i can told you that this function of playing 24bit 96Khz FLAC is a good thing, even if it downgrade or drop to 44Khz. This should just be written somewhere clearly.

And for the 24bit WAV is there any type of downgrade?


Thanks seanadams

seanadams
2008-08-11, 12:58
If i understand when a 24bit 96Khz FLAC play, the DUET read them as 44Khz and drop the rest. So the extra informations are not processed at all, right?

No, what happens is that a sampling effect called "aliasing" causes all the material above the nyquist (>22KHz) to get "folded down" into the audible band. It is not a correct downsampling algorithm in any way, shape, or form. This is all beside the fact though, because the CPU can't decode 24/96 in real time.

Pale Blue Ego
2008-08-11, 15:15
The best way to handle 24/96 with the Duet or SB3 is to create a 2nd copy of the tracks downsampled to 24/48. The Duet will handle those quite nicely and you may be hard pressed to tell the difference.

Doermann
2008-08-11, 15:15
Ok, good.

And for WAV?

Thanks again.

Doermann
2008-08-11, 15:18
The best way to handle 24/96 with the Duet or SB3 is to create a 2nd copy of the tracks downsampled to 24/48. The Duet will handle those quite nicely and you may be hard pressed to tell the difference.

Yes thats what i understand. And i doubt i could tell any difference between them anyway. This is just for my information of how the DUET is working 24bit audio.

Thanks.