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Digital audio out

 
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phlashgringo



Joined: 26 Mar 2009
Posts: 4
PostPosted: Thu Mar 26, 2009 4:41 am    Post subject: Digital audio out Reply with quote
Hi,

Since I found nothing about it, I thought I might ask here.
Is there or has there been a project like realising a digital audio out for the psp.
I guess the sio port is too slow. But it should be possible for stereo signal over usb port.
Is there such a project, and if no - why not?
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Torch



Joined: 28 May 2008
Posts: 842
PostPosted: Thu Mar 26, 2009 10:03 pm    Post subject: Reply with quote
There is a sample by moonlight which can capture the audio output. There are plenty of examples on how to communicate with USB. There is enough bandwidth to pump out the uncompressed audio through USB. Only thing is you need a custom program on the host side. Unless you take the effort to present a usb audio device to the host.
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J.F.



Joined: 22 Feb 2004
Posts: 2906
PostPosted: Fri Mar 27, 2009 7:25 am    Post subject: Reply with quote
Something Torch touched on is the main reason why not - you don't just have to write code for the PSP, you need to write a driver for the PC side as well. Very few people can write Windows drivers, and even fewer can write drivers for other OSes.
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phlashgringo



Joined: 26 Mar 2009
Posts: 4
PostPosted: Fri Mar 27, 2009 8:40 am    Post subject: Reply with quote
maybe I didn't make myself clear - my wish is to push the digital audio signal out from the psp (over the usb plug - since there's no alternative) and plug it direclty - over some fancy adapter thing - into a av receivers digital coax in.
The adapter thing should be nothing more than a soldered cable connection.
Maybe some active or passive devices (resistor) for the right voltage level.
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Torch



Joined: 28 May 2008
Posts: 842
PostPosted: Fri Mar 27, 2009 1:46 pm    Post subject: Reply with quote
There is no way you can manipulate a standard USB port at that level as it uses differential levels. Only specially designed hardware can do this (even then it would simply be a USB plug on the cable and not actual USB communication).
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phlashgringo



Joined: 26 Mar 2009
Posts: 4
PostPosted: Fri Mar 27, 2009 8:50 pm    Post subject: Reply with quote
>even then it would simply be a USB plug on the cable and not actual USB communication

I don't want actual USB connection. I just want the usb plug :)

>There is no way you can manipulate a standard USB port at that level as it uses differential levels.

What do you mean by differential levels. Just to satisfy my greed for understanding:
Now - is it possible to send pure raw (user generated) bitwise data over the usb port. If this is possible everything else should be no problem
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Torch



Joined: 28 May 2008
Posts: 842
PostPosted: Fri Mar 27, 2009 9:21 pm    Post subject: Reply with quote
phlashgringo wrote:
What do you mean by differential levels. Just to satisfy my greed for understanding:
Now - is it possible to send pure raw (user generated) bitwise data over the usb port. If this is possible everything else should be no problem


The voltage produced at the Tx/Rx is the output after the hardware level protocol packaging. You wouldn't be able to to communicate with non-USB compliant hardware unlike a serial port which can be wired up to all kinds of inputs since you have direct control of on/off on the pins. Unfortunately the serial port is too slow for your needs.

I think the only thing you can do is manipulate the headphone out. Capture the audio in software, prevent it from playing through the output (if thats even possible; maybe mute the channel in use while still being able to capture data??) Convert the captured audio into spdif data and turn it into a waveform. Play the waveform and you should have spdif output at the headphone socket. You'll need a level converter or whatever to convert the voltages at the headphone output to spdif standards.
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phlashgringo



Joined: 26 Mar 2009
Posts: 4
PostPosted: Sat Mar 28, 2009 12:09 am    Post subject: Reply with quote
Quote:
The voltage produced at the Tx/Rx is the output after the hardware level protocol packaging.

Oh, bad luck - so there is no way for unpackaged raw data, I see.

Thanks for your idea with the headphone jack. Do you maybe have a good information source at hand for psp system programming resources. I think I have something lying around ... but if you got something relating in your pocket - you're welcome :)
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jean



Joined: 05 Jan 2008
Posts: 489
PostPosted: Sat Mar 28, 2009 9:28 pm    Post subject: Reply with quote
Quote:
Capture the audio in software, prevent it from playing through the output

...Maybe you could simply hook some waveform playing api function...
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