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Author Topic: WASAPI in Windows 7 - JRM Audio & Video  (Read 3004 times)

BushPilot

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WASAPI in Windows 7 - JRM Audio & Video
« on: September 15, 2010, 01:59:37 pm »

I am a little confudsed using wasapi in JRM 15. I works well with audio using my benchmark dac however when I tried the the "Wildlife in HD" installed with JRM, audio sputtering took place. When I disabled exclusive mode in Windows 7, both audio and video work as expected. So, does JRM do the exclusive thing and bypass windows kmixer for both audio & video processing?

Sorry, should have checked cd audio playback. Online radio and video work well with exclusive move disabled in windows. However, when I went to cd quality playback audio would not work and I received onscreen instructions to change DSP settings. Once I enabled exclusive mode in windows again, the audio works but Video sputters on play. Kernal streaming works well for both audio and video. The question I have is, does kernal streaming do the same thing as wasapi and bypass windows kmixer?

Finally got everything working with wasapi with help from others in this forum and an answer to wasapi and kernal streaming as well.





Bill
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Blue Boy

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Re: WASAPI in Windows 7 - JRM Audio & Video
« Reply #1 on: September 15, 2010, 05:16:25 pm »

I asked my DAC manufactor the same question and they gave the advice that if WASAPI is provided
that is the way to go, otherwise Kernel streaming. What differs the two settings I haven't a clue,
some reports from this board can hear a difference soundwise...But I would also want to know what the difference there is betwen the both.
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Alex B

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Re: WASAPI in Windows 7 - JRM Audio & Video
« Reply #2 on: September 15, 2010, 05:35:17 pm »

WASAPI (exclusive), Kernel Streaming and ASIO (if the audio device supports ASIO) bypass the Windows mixer and its DSP features. The played stream is outputted in an unaltered form. There is no reason to expect any audio quality differences between these modes. If one of these output modes happens to work without problems you can simply use it.

I can only imagine that an oddly behaving HW device would change its behavior according to the output mode in certain circumstances, but that is unlikely.
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Blue Boy

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Re: WASAPI in Windows 7 - JRM Audio & Video
« Reply #3 on: September 15, 2010, 05:53:27 pm »

Thank you for an quick answer, but (as english is not my native languise)
1) Are you saying tha there is no difference soundwise?
2) Why two different settings?

I tried kernel streaming and it worked okey for me, but as said in the above, my DAC manufactor recomended WASAPI as the best choice.

I ask this because I have no clue myself, and I'm very new to this, so it is always nice to know.

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Alex B

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Re: WASAPI in Windows 7 - JRM Audio & Video
« Reply #4 on: September 15, 2010, 06:15:26 pm »

I typed the reply hastily, "except" should have been "expect" (it's fixed now).

As I said, you can use the output mode that works correctly. Different hardware may work better with a different output mode (by better I mean functionally better, not better audio quality).

Quote
DAC manufactor recomended WASAPI as the best choice

Did they explain why?
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Blue Boy

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Re: WASAPI in Windows 7 - JRM Audio & Video
« Reply #5 on: September 15, 2010, 06:37:38 pm »

No they didn't, hence my question, the only answer was that they recomended Wasapi......who is behind
Wasapi and who is behind Kernel? Is both Windows origins?
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Alex B

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Re: WASAPI in Windows 7 - JRM Audio & Video
« Reply #6 on: September 15, 2010, 07:03:55 pm »

WASAPI means Windows Audio Session API. It is the name of the redesigned audio system in Vista and Windows 7.

Kernel streaming is an output mode that can bypass the Kernel mixer in older Windows operating systems. The "mixer" in WASAPI is not named as Kernel mixer but the Kernel streaming output mode works correctly also in Vista and Windows 7.

More info:
WASAPI  http://en.wikipedia.org/wiki/Technical_features_new_to_Windows_Vista#Audio
Kernel Streaming  http://en.wikipedia.org/wiki/Kernel_streaming

In general, WASAPI in Vista and Windows 7 has many redesigned, possibly improved, signal processing features, but those are bypassed when the Exlusive mode is used and thus WASAPI Exclusive and Kernel Streaming should both provide unaltered audio quality.
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