looking for "linux audio device" with digital output


daniel.m

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Hei everybody!


Hope one of you geeks can help me here ;) ... my knowledge is not really that extensive when it comes to low level hardware stuff, but I hope that the developers of the Pandora are not the only people here who could help me. I'm looking for a "Linux device" that has USB, SATA and VGA connectors as well as digital audio output. Probably something similar to the Pandora or Beagle board. Well, the device is meant to be built into a high-end amplifier and that's why I need to have digital audio output.


To be more precise, it should


- be able to play back a broad variety of audio files from memory sticks, a built in hard disk, a CD-drive


- have DVI or HDMI output to connect a small LCD (only 2D, nothing fancy)


- have digital audio output!


So far I have only found single-board computers and audio players that don't meet the last criterion.


And I have another question regarding boot up time: is it possible to get a Linux running that will only perform audio playback tasks and boot extremely quickly (a low power standby mode would also be acceptable).


Sorry if this sounds weird, but I am trying to help out someone and I will not be involved in hardware/software development. The problem is not building the audio player and programming software for it but finding suitable hardware.


Suggestions are highly appreciated! :)
 
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Sounds interesting, but S/PDIF seems to be input only. Apart from that I'd like to avoid VIA, Nvidia and Intel B)


Size doesn't matter that much, but power consumption is very important. The amplifier will produce a lot of heat and the "audio device" should not have a "problem" with heat itself (= need a huge heat sink or even active cooling).


Well, I just stumbled over a USB to S/PDIF converter. If playback would be digital all the way to S/PDIF, that would also be a possibility. Here I lack knowledge again ... I assume that USB can only output digital signals and that, when you connect a "USB audio class device", a digital audio stream could be directed to a USP port. Or is there an A/D-converter sitting in-between that will convert the digital audio stream to an analogue signal that will be connected to the USB-port? (I have a feeling that this is a stupid question, but I want to be sure that audio stays digital all the way without being converted to an analogue signal)


In short: Can I "tell" Linux to output an audio stream to USB and then convert that digital output to S/PDIF with an additional chip like PCM2902?
 
Sounds interesting, but S/PDIF seems to be input only. Apart from that I'd like to avoid VIA, Nvidia and Intel B)


Size doesn't matter that much, but power consumption is very important. The amplifier will produce a lot of heat and the "audio device" should not have a "problem" with heat itself (= need a huge heat sink or even active cooling).


Well, I just stumbled over a USB to S/PDIF converter. If playback would be digital all the way to S/PDIF, that would also be a possibility. Here I lack knowledge again ... I assume that USB can only output digital signals and that, when you connect a "USB audio class device", a digital audio stream could be directed to a USP port. Or is there an A/D-converter sitting in-between that will convert the digital audio stream to an analogue signal that will be connected to the USB-port? (I have a feeling that this is a stupid question, but I want to be sure that audio stays digital all the way without being converted to an analogue signal)


In short: Can I "tell" Linux to output an audio stream to USB and then convert that digital output to S/PDIF with an additional chip like PCM2902?


Well I downloaded the manual for this, I'm interested myself in getting one of these.. they're is a SPDIF OUT pin on a multi-media daughter-board connector. the PDF states it's pin 54.. I'm not sure you may be able to run a jumper directly from this pin or just get the optional multimedia daughter-board.


Direct PDF


http://www.via.com.tw/servlet/downloadSvl?id=472&download_file_id=5801


from page


http://www.via.com.tw/en/products/embedded/ProductDetail.jsp?id=472

In short: Can I "tell" Linux to output an audio stream to USB and then convert that digital output to S/PDIF with an additional chip like PCM2902?

You would need to write a driver to handle something like this, there are USB sound cards availible that have digital out, although the only one I see right off a google search only has optical out.. http://www.turtlebeach.com/products/sound-cards/audio-advantage-micro-ii.aspx
 
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S/PDIF can be transmitted over either coax or TOSLINK optical - and these days any random optical audio out port you find on a consumer device is probably supplying an S/PDIF audio stream.


Re USB audio; USB is a digial only medium, so a USB audio to S/PDIF convertor really out not to contain any A/D or D/As.


Re Linux drivers, I have a set of USB headphones and my install of Fedora recognised them without installing any non-standard drivers. USB audio is apparently an official USB device class, like HID (for mouse/kbd) or mass storage (for external discs etc.). I'd hope most mature USB implementations would have built in support for it (except for Windows of course, which even needs to install a separate driver for mass storage devices).
 
S/PDIF can be transmitted over either coax or TOSLINK optical - and these days any random optical audio out port you find on a consumer device is probably supplying an S/PDIF audio stream.


Re USB audio; USB is a digial only medium, so a USB audio to S/PDIF convertor really out not to contain any A/D or D/As.


Re Linux drivers, I have a set of USB headphones and my install of Fedora recognised them without installing any non-standard drivers. USB audio is apparently an official USB device class, like HID (for mouse/kbd) or mass storage (for external discs etc.). I'd hope most mature USB implementations would have built in support for it (except for Windows of course, which even needs to install a separate driver for mass storage devices).

what he wanted to do was directly connect USB cable and expect it to work right.. He needs to get a USB audio device to handle the digital out. I've had good luck with USB audio devices in Linux.
 
Re USB audio; USB is a digial only medium, so a USB audio to S/PDIF convertor really out not to contain any A/D or D/As.
Good, just wanted to be 110% sure :D

Re Linux drivers, I have a set of USB headphones and my install of Fedora recognised them without installing any non-standard drivers. USB audio is apparently an official USB device class, like HID (for mouse/kbd) or mass storage (for external discs etc.). I'd hope most mature USB implementations would have built in support for it (except for Windows of course, which even needs to install a separate driver for mass storage devices).
That is what I found out too. Sounds like I could use just any single-board computer with a USB S/PDIF converter :)

what he wanted to do was directly connect USB cable and expect it to work right.. He needs to get a USB audio device to handle the digital out. I've had good luck with USB audio devices in Linux.
No, I wanted to use a converter (like the PCM2902 I mentioned before), not a USB cable directly.
 
Good, just wanted to be 110% sure :D


That is what I found out too. Sounds like I could use just any single-board computer with a USB S/PDIF converter :)


No, I wanted to use a converter (like the PCM2902 I mentioned before), not a USB cable directly.

It would require building the supporting circuitry for the chip on a circuit or pro-typing board.. if you want to go through all that or buy a $24 - $35 prebuilt device off newegg.com
 
It would require building the supporting circuitry for the chip on a circuit or pro-typing board.. if you want to go through all that or buy a $24 - $35 prebuilt device off newegg.com
Building that converter is not a problem, and maybe we can even build the computer ourselves ...
 
Building that converter is not a problem, and maybe we can even build the computer ourselves ...

Well I mean that's a good project, but building a computer from component level is very difficult, especially how most components now require surface mount soldering or components so small that it would require robotics to solder them properly. If you built a computer with components that are easily solder-able or can fit on a prototype board it will about be 4 times the size of one using surface mount components.


The small computerboard I posted above DOES have SPDIF out, just on a multimedia connector.. Not to mention this was just the first one that I found in a google search. Both Via, Intel and several other companies have a good selection of Mini/ultra small computer solutions that could be easily adapted to your project.


But don't let me squash your ideas, Like I said It could be a good project to build something on your own.
 
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Well I mean that's a good project, but building a computer from component level is very difficult, especially how most components now require surface mount soldering or components so small that it would require robotics to solder them properly. If you built a computer with components that are easily solder-able or can fit on a prototype board it will about be 4 times the size of one using surface mount components.


The small computerboard I posted above DOES have SPDIF out, just on a multimedia connector.. Not to mention this was just the first one that I found in a google search. Both Via, Intel and several other companies have a good selection of Mini/ultra small computer solutions that could be easily adapted to your project.


But don't let me squash your ideas, Like I said It could be a good project to build something on your own.
Don't worry, you didn't squash anything :)


This is not a private project, so we will either design a mainboard and let someone else produce it or buy mainboards from some other company. Even though I'm still not sure if it is feasible since it would involve a lot of work and might not be worth it for the few devices that would be produced.


But thanks for all the comments!
 
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