ALSA layer in Linux 2.6.18 and OSS

ALSA layer in Linux 2.6.18 and OSS

[Viral Mehta]

Hi All,

I am trying to make an application that does Audio playback and record. 
I have configured Kernel and Re-built it.
I want to use only ALSA features. I have said "Yes" to all ALSA related 
options and "No" to all OSS related things.

When I booted my kernel, I found that there was no "/dev/dsp" device and 
so my application was not able to run. The application opens "/dev/dsp" 
device first and then does other things.

Next time, when I enabled few of the OSS options in kernel's config 
file. I was able to run my application. My question is I do not want OSS 
at all. I just need ALSA then in that case what I am doing wrong.

Thanks,
Viral


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Re: ALSA layer in Linux 2.6.18 and OSS

[Takashi Iwai]

At Mon, 16 Feb 2009 13:24:54 +0530,
Viral Mehta wrote:
> 
> Hi All,
> 
> I am trying to make an application that does Audio playback and record. 
> I have configured Kernel and Re-built it.
> I want to use only ALSA features. I have said "Yes" to all ALSA related 
> options and "No" to all OSS related things.
> 
> When I booted my kernel, I found that there was no "/dev/dsp" device and 
> so my application was not able to run. The application opens "/dev/dsp" 
> device first and then does other things.
> 
> Next time, when I enabled few of the OSS options in kernel's config 
> file. I was able to run my application. My question is I do not want OSS 
> at all. I just need ALSA then in that case what I am doing wrong.

Well, rather a real question is which app / subsystem accessing the
OSS device and causes errors.  You can set up ALSA-only system in the
kernel side.  But if the user-space side requires the OSS API, it
won't work.

So,
- if you want to remove all OSS-accessing apps, fix them
or
- build ALSA OSS *emulation* module so that they work both
or
- use aoss wrapper instead


Takashi

Re: ALSA layer in Linux 2.6.18 and OSS

[Viral Mehta]

Takashi Iwai wrote:
> At Mon, 16 Feb 2009 13:24:54 +0530,
> Viral Mehta wrote:
>   
>> Hi All,
>>
>> Next time, when I enabled few of the OSS options in kernel's config 
>> file. I was able to run my application. My question is I do not want OSS 
>> at all. I just need ALSA then in that case what I am doing wrong.
>>     
>
> Well, rather a real question is which app / subsystem accessing the
> OSS device and causes errors.
Thanks for quick response. Well, I myself am writing Audio Player 
application for some embedded device.
I generally used to write open("/dev/dsp") device and then do read/write 
of RAW data on that device and it used to work till now.
I was/am doing so and completely unaware of OSS/ALSA.
>   You can set up ALSA-only system in the
> kernel side.  
But then when I found while rebuilding kernel that there are two sound 
sub-system OSS and ALSA.
ALSA is a new one and OSS is deprecated. And so I thought to remove 
everything about OSS from Kernel.
> But if the user-space side requires the OSS API, it
> won't work.
>
>   
So, I guess my application is such that it wont work with ALSA-only-kernel.
But then on contrary, I think that opening a /dev/dsp and throwing data 
is a simple way AND what is so wrong in that and why ALSA-only-kernel 
cant understand that ?
> So,
> - if you want to remove all OSS-accessing apps, fix them
> or
> - build ALSA OSS *emulation* module so that they work both
> or
> - use aoss wrapper instead
>
>   









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__________________________________________________________________________

Re: ALSA layer in Linux 2.6.18 and OSS

[Takashi Iwai]

At Mon, 16 Feb 2009 16:27:06 +0530,
Viral Mehta wrote:
> 
> 
> 
> Takashi Iwai wrote:
> > At Mon, 16 Feb 2009 13:24:54 +0530,
> > Viral Mehta wrote:
> >   
> >> Hi All,
> >>
> >> Next time, when I enabled few of the OSS options in kernel's config 
> >> file. I was able to run my application. My question is I do not want OSS 
> >> at all. I just need ALSA then in that case what I am doing wrong.
> >>     
> >
> > Well, rather a real question is which app / subsystem accessing the
> > OSS device and causes errors.
> Thanks for quick response. Well, I myself am writing Audio Player 
> application for some embedded device.
> I generally used to write open("/dev/dsp") device and then do read/write 
> of RAW data on that device and it used to work till now.
> I was/am doing so and completely unaware of OSS/ALSA.
> >   You can set up ALSA-only system in the
> > kernel side.  
> But then when I found while rebuilding kernel that there are two sound 
> sub-system OSS and ALSA.
> ALSA is a new one and OSS is deprecated. And so I thought to remove 
> everything about OSS from Kernel.

In that case, simply enable ALSA OSS emulation modules, the second
case below.  Then OSS API will work on the top of ALSA subsystem.


Takashi

> > But if the user-space side requires the OSS API, it
> > won't work.
> >
> >   
> So, I guess my application is such that it wont work with ALSA-only-kernel.
> But then on contrary, I think that opening a /dev/dsp and throwing data 
> is a simple way AND what is so wrong in that and why ALSA-only-kernel 
> cant understand that ?
> > So,
> > - if you want to remove all OSS-accessing apps, fix them
> > or
> > - build ALSA OSS *emulation* module so that they work both
> > or
> > - use aoss wrapper instead
> >
> >   
> 
> 
> 
> 
> 
> 
> 
> 
> 
> -- 
> _____________________________________________________________________
> Disclaimer: This e-mail message and all attachments transmitted with it
> are intended solely for the use of the addressee and may contain legally
> privileged and confidential information. If the reader of this message
> is not the intended recipient, or an employee or agent responsible for
> delivering this message to the intended recipient, you are hereby
> notified that any dissemination, distribution, copying, or other use of
> this message or its attachments is strictly prohibited. If you have
> received this message in error, please notify the sender immediately by
> replying to this message and please delete it from your computer. Any
> views expressed in this message are those of the individual sender
> unless otherwise stated.Company has taken enough precautions to prevent
> the spread of viruses. However the company accepts no liability for any
> damage caused by any virus transmitted by this email.
> __________________________________________________________________________
>  
> 

Re: ALSA layer in Linux 2.6.18 and OSS

[Colin Guthrie]

'Twas brillig, and Viral Mehta at 16/02/09 10:57 did gyre and gimble:
> Thanks for quick response. Well, I myself am writing Audio Player 
> application for some embedded device.

This recent article may make for interesting reading for you:

  http://0pointer.de/blog/projects/guide-to-sound-apis.html

Col


-- 

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gmane(at)colin.guthr.ie
http://colin.guthr.ie/

Day Job:
   Tribalogic Limited [http://www.tribalogic.net/]
Open Source:
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   PulseAudio Hacker [http://www.pulseaudio.org/]
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Re: ALSA layer in Linux 2.6.18 and OSS

[James Courtier-Dutton]

2009/2/16 Viral Mehta <viral.mehta@einfochips.com>:
> Hi All,
>
>
> When I booted my kernel, I found that there was no "/dev/dsp" device and
> so my application was not able to run. The application opens "/dev/dsp"
> device first and then does other things.
>

/dev/dsp is the OSS API. So an install without OSS will not have /dev/dsp.
An application that supports alsa will link to libasound.
If you have an OSS application that you want to work with ALSA, you
need to add the ALSA OSS emulation layer.

Re: ALSA layer in Linux 2.6.18 and OSS

[Viral Mehta]

James Courtier-Dutton wrote:
> 2009/2/16 Viral Mehta <viral.mehta@einfochips.com>:
>   
>> Hi All,
>>
>>
>> When I booted my kernel, I found that there was no "/dev/dsp" device and
>> so my application was not able to run. The application opens "/dev/dsp"
>> device first and then does other things.
>>
>>     
>
> /dev/dsp is the OSS API. So an install without OSS will not have /dev/dsp.
> An application that supports alsa will link to libasound.
> If you have an OSS application that you want to work with ALSA, you
> need to add the ALSA OSS emulation layer.

So, the last question.
Is it possible to write an application totally using ALSA user and 
kernel things (i.e., without having OSS emulation layer)?

In that case, if application will not open /dev/dsp then what ll it do ? 
Just pointers will be great for me.

And will it be possible to implement full-featured application which 
plays stereo and also provides equalizer and etc just by using ALSA ?
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_____________________________________________________________________
Disclaimer: This e-mail message and all attachments transmitted with it
are intended solely for the use of the addressee and may contain legally
privileged and confidential information. If the reader of this message
is not the intended recipient, or an employee or agent responsible for
delivering this message to the intended recipient, you are hereby
notified that any dissemination, distribution, copying, or other use of
this message or its attachments is strictly prohibited. If you have
received this message in error, please notify the sender immediately by
replying to this message and please delete it from your computer. Any
views expressed in this message are those of the individual sender
unless otherwise stated.Company has taken enough precautions to prevent
the spread of viruses. However the company accepts no liability for any
damage caused by any virus transmitted by this email.
__________________________________________________________________________