Pc -> Dac, How ?

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#161
And you wonder why most people still use CDs?

Seven pages of completely incomprehensible gobbledygook which the average Joe Schmoe hasn't got a clue about.

Get in the real world guys and start listening to music instead of fiddling around with your Operating Systems and low latency Linux embedded kernel drivers.
 
#163
Audio Gateway kit

Guys
Here it is one interesting kit from Atmel and pretty cheap!
http://www.eetimes.eu/products/analog/215900841

Consider this board as ethernet to i2s
audio streaming player.
Player gets data (wav up to24/192) from external NAS. External DAC connected on I2S as master.
And pretty cheap!

It's just a project in my head - I'm not software buddy, alas :-(
So i don't know could it process all this stuff.

Respect
 
#168
anbello said:
From what i read in the data sheet of the avr32 (a quick read so i hope to be wrong) i2s samples could be only 16 bit long. Is there anyone who can confirm or refute this?

Ciao
Andrea
Click to expand...


• DATLEN: Data Length
0: Forbidden value (1-bit data length not supported).
Any other value: The bit stream contains DATLEN + 1 data bits. Moreover, it defines the transfer size performed by the
PDC2 assigned to the Transmit. If DATLEN is lower or equal to 7, data transfers are bytes, if DATLEN is between 8 and 15
(included), half-words are transferred, and for any other value, 32-bit words are transferred.

That means up to 32bit words are possible. 🙂

Cheers!
Russ
 
#170
Thanks for the explanation Russ, i was confused also reading at the alsa driver source for atmel soc.

An excerpt from alsa-driver-1.0.19\alsa-kernel\soc\atmel\atmel_ssc_dai.c

/*
* The SSC only supports up to 16-bit samples in I2S format, due
* to the size of the Frame Mode Register FSLEN field.
*/
if ((ssc_p->daifmt & SND_SOC_DAIFMT_FORMAT_MASK) == SND_SOC_DAIFMT_I2S
&& bits > 16) {
printk(KERN_WARNING
"atmel_ssc_dai: sample size %d"
"is too large for I2S\n", bits);
return -EINVAL;
}

Ciao
Andrea
 
#173
Because i would like to use an avr32 based board or an AT91SAM9260 based board like this with linux using alsa driver.
From the source of the alsa driver i see that it's possible to use these MCUs with the SSC in slave mode (BCLK and LRC clocks as input) only in i2s mode. Using it in slave mode is a necessity to have low jitter.
I hope that some next release of alsa implement the other modes that you pointed.

Ciao
Andrea
 
#174
-- To francolargo
You're right sounds almoste like Squeezebox, but
1. Squeezebox - doesn't support anything higher than 24/96
2. Squeezebox doesn't support I2S (wo modification).
3. Is it Squeezebox bit-to-bit perfect?

And I'm completly satisfied with wav files on the NAS.
If audio in wav files then less processing on CPU.

-- To Russ White
Do you have plans to make some software package for this Atmel kit? Or may be it's gonna be a ethernet media player based on this Atmel Kit?
It's all sounds interesting because for the last month I try to make desicion what to choose: stand alone media player or silent audio PC.
 
#176
anbello said:
Because i would like to use an avr32 based board or an AT91SAM9260 based board like this with linux using alsa driver.
From the source of the alsa driver i see that it's possible to use these MCUs with the SSC in slave mode (BCLK and LRC clocks as input) only in i2s mode. Using it in slave mode is a necessity to have low jitter.
I hope that some next release of alsa implement the other modes that you pointed.

Ciao
Andrea
Click to expand...

It would be quite easy to modify the alsa code to do RJ or LJ. Or even to do I2S without the word clock being driven in pulse mode.

I will probably just rewrite that portion of the driver. No problem.
 
#178
Russ White said:


It would be quite easy to modify the alsa code to do RJ or LJ. Or even to do I2S without the word clock being driven in pulse mode.

I will probably just rewrite that portion of the driver. No problem.
Click to expand...


It would be great!

Russ, based on your experience, what could be the limit of the AT91SAM9260 based board linked by me in term of samplerate and bit depth? 48/24? 96/24?

Ciao
Andrea
 
#179
francolargo,
I'm in the same boat - only questions ... who know the answers?

In press release for ATEVK1105 Digital Audio Gateway Kit Atmel says:
... MP3 decoding from a USB mass storage device requires only a third of the AVR32’s processing capacity, leaving plenty of headroom for running the operation system, streaming the data and refreshing the display.
 
#180
anbello said:



It would be great!

Russ, based on your experience, what could be the limit of the AT91SAM9260 based board linked by me in term of samplerate and bit depth? 48/24? 96/24?

Ciao
Andrea
Click to expand...


I have not used that uC, but I think that 96/24 is certainly in the realm of possibility. 🙂

FLAC is relatively computationally inexpensive. It is all integer math on the decode side. So no floating point to worry about.

I did not get very far in my last project I basically just got the decoder working when I got distracted by something else. 🙂

Cheers!
Russ
 
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