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Author Topic: ASIO output and DSP  (Read 5706 times)

PLuft

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ASIO output and DSP
« on: February 19, 2008, 06:24:26 pm »
Hello,

Based on what I can see, ASIO seems to output every audio file only as 32bit.   If I *deliberately* disable my audio card in device manager, disable all DSP effects, and attempt to play a 16bit audio file using ASIO, I receive the following message:

Playback could not be started on the output 'ASIO' using format '44100 Hz, 32 Bits Per Sample, 2 Channels

Does this mean that ASIO always outputs 16bit files as 32bit?  If I enable 'Output Format' in DSP and select a bitdepth of 16bit, I still receive an error message about 32 Bits Per Sample. 

If I attempt to playback a 16bit audio file using Direct Sound with all DSP effects off, the error message correctly states MC can't ouput using '44100 Hz, 16 Bits Per Sample'

Although this is a little picky on my part, I'd rather have 16bit files output as 16bit via ASIO.   Am I missing something obvious here?  If so, my apologies.  I am using MC 12.0.438.

Thank you.
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JimH

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Re: ASIO output and DSP
« Reply #1 on: February 19, 2008, 06:58:57 pm »
OK.  I own the company and I can barely follow your question.  But Welcome to Interact and why have you waited so long to post?

The point of ASIO is to output an unmodified bitstream to the device.  I'm pretty confident we do that.

MC uses a 32 bit data path internally to route all audio.  That isn't related to how the audio file is _stored_.

I expect to be corrected any moment by the real experts here, but I think you can just set MC to ASIO and let it fly.
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jgreen

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Re: ASIO output and DSP
« Reply #2 on: February 19, 2008, 07:27:03 pm »
Pluft, I'm no expert either, but the experts are running a little slow today.  It's cold out and audio expertise is a little bit like tree sap in that regard.

I'm not sure you're actually set up for ASIO.  Under "tools/options/playback/audio", once you select "asio" under "output mode", did you go to the second option "output mode settings" and identify your ASIO (software) device? 
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JimH

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Re: ASIO output and DSP
« Reply #3 on: February 19, 2008, 07:36:55 pm »
Quote from: jgreen on February 19, 2008, 07:27:03 pm
audio expertise is a little bit like tree sap
I said I would be corrected shortly.
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Matt

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Re: ASIO output and DSP
« Reply #4 on: February 19, 2008, 07:44:09 pm »
Quote from: PLuft on February 19, 2008, 06:24:26 pm
Hello,

Based on what I can see, ASIO seems to output every audio file only as 32bit.   If I *deliberately* disable my audio card in device manager, disable all DSP effects, and attempt to play a 16bit audio file using ASIO, I receive the following message:

Playback could not be started on the output 'ASIO' using format '44100 Hz, 32 Bits Per Sample, 2 Channels

Does this mean that ASIO always outputs 16bit files as 32bit?  If I enable 'Output Format' in DSP and select a bitdepth of 16bit, I still receive an error message about 32 Bits Per Sample. 

If I attempt to playback a 16bit audio file using Direct Sound with all DSP effects off, the error message correctly states MC can't ouput using '44100 Hz, 16 Bits Per Sample'

Although this is a little picky on my part, I'd rather have 16bit files output as 16bit via ASIO.   Am I missing something obvious here?  If so, my apologies.  I am using MC 12.0.438.

Thank you.


Each sound card defines a native buffer format that ASIO data must be delivered in.

In your case, it sounds like you have a 32-bit card.  This is good -- it means 16, 24, and 32 bit playback will all be bit perfect.  Remember that changing the bit-depth from 16 to 32 is a perfectly lossless transform.

As Jim mentioned, MC actually always uses 32-bits for the audio internally.  It then converts to the appropriate bit-depth at output time.  This approach remains bit-perfect if no DSP is applied, but can produce better S/N ratios when effects are applied or the input material is of better quality.

Hopefully this makes some sense.  Basically, the comment about setting ASIO and letting it fly is correct.

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Matt Ashland, JRiver Media Center

PLuft

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Re: ASIO output and DSP
« Reply #5 on: February 20, 2008, 05:32:39 pm »
Hi Matt,

Thank you for the response.  I think that makes sense.  It's nice to know it isn't a bug with Media Center. 

Actually, I have a 24-bit card.  A CardDeluxe by Digital Audio. 

Cheers,

Pat
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Alex B

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Re: ASIO output and DSP
« Reply #6 on: February 20, 2008, 06:12:39 pm »
Quote from: PLuft on February 20, 2008, 05:32:39 pm
Hi Matt,

Thank you for the response.  I think that makes sense.  It's nice to know it isn't a bug with Media Center. 

Actually, I have a 24-bit card.  A CardDeluxe by Digital Audio.

It makes sense, but didn't you have an actual problem that is not solved yet? I mean if you get the "playback could not be started" message you can't play?

Quote from: PLuft on February 19, 2008, 06:24:26 pm
Hello,

Based on what I can see, ASIO seems to output every audio file only as 32bit.   If I *deliberately* disable my audio card in device manager, disable all DSP effects, and attempt to play a 16bit audio file using ASIO, I receive the following message:

Playback could not be started on the output 'ASIO' using format '44100 Hz, 32 Bits Per Sample, 2 Channels

Does this mean that ASIO always outputs 16bit files as 32bit?  If I enable 'Output Format' in DSP and select a bitdepth of 16bit, I still receive an error message about 32 Bits Per Sample.

What you mean by "deliberately disabling audio card in device manager"? I don't think it can work at all if you do that. Or did you do that only for testing and when you enable the card it works normally?

Quote
If I attempt to playback a 16bit audio file using Direct Sound with all DSP effects off, the error message correctly states MC can't ouput using '44100 Hz, 16 Bits Per Sample'

I suppose also this happens only when you deliberately disable the card. Correct?

If you have a problem did you do what jgreen suggested? What are your exact settings in MC's Output Mode settings? Are you using the card manufacturer's ASIO driver?
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PLuft

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Re: ASIO output and DSP
« Reply #7 on: February 20, 2008, 06:35:55 pm »
HI Alex,

I appreciate your response.

I wasn't concerned about the error message, and would expect an error from Media Center because I disabled the card.  I was more concerned about the content of the error message - Since I wasn't using DSP at all, why was Media Center trying to output audio from a 16bit audio file as 32 bit?  The error message stated it couldn't output 32bit data using ASIO.   So... my assumption was Media Center normally ouput 32 bit audio all the time with ASIO when my audio card is enabled and working normally. 

Not to confuse the issue further, but my audio card has a configuation section that will restrict audio output to either 16bit or 24bit.  If I select 16bit, ASIO doesn't work under any circumstances via Media Center, with all DSP settings disabled.  I assume this is because of what Matt said - that it's expecting a 32 bit buffer?

Anyway, I was just concerned about the audio being 'bit-perfect' and apparently it is, based on Matt's response.  Sorry, I should have quoted his response. 

Regards,

Pat



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Alex B

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Re: ASIO output and DSP
« Reply #8 on: February 20, 2008, 07:04:44 pm »
As Matt said, in this case the bit-depth is irrelevant to the bit-perfectness. When a 16-bit signal is output in 32-bit format (without any DSP alterations) only the 16 topmost bits contain signal. The lower bits are padded with zeros. A 24-bit sound card just drops the eight lowest bits. Actually, I don't think any sound card can output real 32-bit signal.
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Ripper

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Re: ASIO output and DSP
« Reply #9 on: February 22, 2008, 12:37:46 pm »
    I have Windows Vista Home Premium 32-bit and an M-Audio Delta Audiophile 192 sound card.  I don't think that I can select ASIO output, but I would like unadulterated, bit-perfect audio to stream out of my card.  Is this possible?  If not, is it Vista's fault?  Is there a way around this?

    Thanks.


Quote from: JimH on February 19, 2008, 06:58:57 pm
OK.  I own the company and I can barely follow your question.  But Welcome to Interact and why have you waited so long to post?

The point of ASIO is to output an unmodified bitstream to the device.  I'm pretty confident we do that.

MC uses a 32 bit data path internally to route all audio.  That isn't related to how the audio file is _stored_.

I expect to be corrected any moment by the real experts here, but I think you can just set MC to ASIO and let it fly.

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