MPEG Support

MPEG Support

[Kurt Wall]

Hello, all,

Does the 2.2.x sound driver yet support MPEG?  Or is this being coded up in
ALSA (I've not looked at this) or video-for-linux?

On a related question, does anyone know the current status of the
programmer's guide to the OSS API?  I saw a blurb on their site
(http://www.opensound.com/pguide/index.html) that it was currently being
updated, but quite some time has passed, and I'm quite sure that it has
become dated.

Thanks and regards,

Kurt
-- 
We totally deny the allegations, and we're trying to identify the allegators.

Re: MPEG Support

[Benno Senoner]

On Tue, 03 Aug 1999, Kurt Wall wrote:
> Hello, all,
> 
> Does the 2.2.x sound driver yet support MPEG?  Or is this being coded up in
> ALSA (I've not looked at this) or video-for-linux?
> 
> On a related question, does anyone know the current status of the
> programmer's guide to the OSS API?  I saw a blurb on their site
> (http://www.opensound.com/pguide/index.html) that it was currently being
> updated, but quite some time has passed, and I'm quite sure that it has
> become dated.
> 
> Thanks and regards,
> 
> Kurt
> -- 

If you are speaking about MPEG audio Layer II / Layer III ( MP2/MP3) , then
you can AND SHOULD do this in userspace.

there are several  MP2/MP3 players arount like freeamp (
http://www.freeamp.org ) , or XMMS  ( http://www.xmms.org )

if you need a great MPEG decoding audio library you can get it
at http://www.xaudio.com
It's one of the fastest around the planet :-)
(Includes pentium optimized decoding routines)

Alternatively you can use the decoding lib of mpg123.

A good MP3 encoder for Linux is Bladeenc (you can find the link at
http://www.mpeg.org )


hope this helps,

regards,
Benno.

Re: MPEG Support

[Jonathan C. Masters]

I have to disagree with you here. I believe that MPEG audio decoding/encoding
and MPEG video decoding/encoding optional devices such as /dev/mpad /dev/mpae
/dev/mpvd /dev/mpve would be emensely useful. It would save so much rewritten
code (libraries are never quite as good as they sound) and my programs would
instantaneously become much more enhanced. Besides, since MPEG decoding/encoding
cards are popular these days, you begin to see the speed required (so much so
that so many cards exist) so putting low level kernel routines into the kernel
would probably be the only way to achieve maximum software "emulation" of these
expensive cards.

Benno Senoner wrote:

> On Tue, 03 Aug 1999, Kurt Wall wrote:
> > Hello, all,
> >
> > Does the 2.2.x sound driver yet support MPEG?  Or is this being coded up in
> > ALSA (I've not looked at this) or video-for-linux?
> >
> > On a related question, does anyone know the current status of the
> > programmer's guide to the OSS API?  I saw a blurb on their site
> > (http://www.opensound.com/pguide/index.html) that it was currently being
> > updated, but quite some time has passed, and I'm quite sure that it has
> > become dated.
> >
> > Thanks and regards,
> >
> > Kurt
> > --
>
> If you are speaking about MPEG audio Layer II / Layer III ( MP2/MP3) , then
> you can AND SHOULD do this in userspace.
>
> there are several  MP2/MP3 players arount like freeamp (
> http://www.freeamp.org ) , or XMMS  ( http://www.xmms.org )
>
> if you need a great MPEG decoding audio library you can get it
> at http://www.xaudio.com
> It's one of the fastest around the planet :-)
> (Includes pentium optimized decoding routines)
>
> Alternatively you can use the decoding lib of mpg123.
>
> A good MP3 encoder for Linux is Bladeenc (you can find the link at
> http://www.mpeg.org )
>
> hope this helps,
>
> regards,
> Benno.

--
Jonathan C. Masters                     (jonathan@oxlug.org)
                                        PGP: www.brookes.ac.uk/~95227860/KEY

           "Upon this rock I will build my church,
            and the gates of hell shall not prevail against it".

                 -- Matthew 16, 17-18

Re: MPEG Support

[Thomas Sailer]

Kurt Wall wrote:

> Does the 2.2.x sound driver yet support MPEG?  Or is this being coded up in
> ALSA (I've not looked at this) or video-for-linux?

Why would it want to? It doesn't make sense to put a software MPEG
decoding engine in the kernel. Only if the hardware has an MPEG
decoder (is there any PC hardware that does this?) it's interface
should be exposed to user space by the sound driver.

Tom

Re: MPEG Support

[Kurt Wall]

Also sprach Jonathan C. Masters:
> I have to disagree with you here. I believe that MPEG audio decoding/encoding
> and MPEG video decoding/encoding optional devices such as /dev/mpad /dev/mpae
> /dev/mpvd /dev/mpve would be emensely useful. It would save so much rewritten
> code (libraries are never quite as good as they sound) and my programs would
> instantaneously become much more enhanced. Besides, since MPEG decoding/encoding
> cards are popular these days, you begin to see the speed required (so much so
> that so many cards exist) so putting low level kernel routines into the kernel
> would probably be the only way to achieve maximum software "emulation" of these
> expensive cards.

The original question I asked was simply if MPEG support had ever been added
to the <linux/soundcard.h>, as some of the declarations therein seemed to
suggest that such support would be added.  I didn't ask for a lecture on
whether or not it is appropriate to add such to the kernel

As it is, I concur with the posters who wrote that this is not appropriate
for the kernel.  The kernel is big enough as it is, but, more to the point,
this is just something that needs to be done in userland or, perhaps,
implemented as a loadable module if you the need for kernel access can be
demonstrated.  There appear to be several good libraries for achieving the
sort of speed necessary for decoding/encoding layer II/III files, so I don't
see the need for more bulk in the kernel.

My $US 1/50.  Thanks to those who replied.

[snippety snip snip]

Kurt
-- 

Re: MPEG Support

[Thomas Sailer]

"Jonathan C. Masters" wrote:
> 
> I have to disagree with you here. I believe that MPEG audio decoding/encoding
> and MPEG video decoding/encoding optional devices such as /dev/mpad /dev/mpae
> /dev/mpvd /dev/mpve would be emensely useful. It would save so much rewritten
> code (libraries are never quite as good as they sound) and my programs would

Why should a library be worse than kernel code?

Furthermore, in the kernel, you can't use:
- MMX
- Floating point
- KNI or ISSE or 3dNOW.

So kernel code will be slower than usermode code.

> instantaneously become much more enhanced. Besides, since MPEG decoding/encoding
> cards are popular these days, you begin to see the speed required (so much so

Please name one that does MPEG _AUDIO_, I don't know one. (I know
about MPEG video cards...)

Tom

Re: MPEG Support

[Kurt Wall]

Also sprach Hannu Savolainen:
> On Thu, 5 Aug 1999, Kurt Wall wrote:
> 
> > The original question I asked was simply if MPEG support had ever been added
> > to the <linux/soundcard.h>, as some of the declarations therein seemed to
> > suggest that such support would be added.  I didn't ask for a lecture on
> > whether or not it is appropriate to add such to the kernel
> The define for MPEG audio was added there for cards with hardware MPEG
> audio capability. At that time (good old 486 days) software MPEG in kernel
> simply was not possible. The definition was added just for future
> purposes.

Well, da man hisself, he done said it.  Thread closed. :-)

Kurt
-- 
Didja' ever have to make up your mind,
Pick up on one and leave the other behind,
It's not often easy, and it's not often kind,
Didja' ever have to make up your mind?
		-- Lovin' Spoonful

Re: MPEG Support

[sbenno]

On Thu, 05 Aug 1999, Thomas Sailer wrote:
> "Jonathan C. Masters" wrote:
> > 
> > I have to disagree with you here. I believe that MPEG audio decoding/encoding
> > and MPEG video decoding/encoding optional devices such as /dev/mpad /dev/mpae
> > /dev/mpvd /dev/mpve would be emensely useful. It would save so much rewritten
> > code (libraries are never quite as good as they sound) and my programs would
> 
> Why should a library be worse than kernel code?
> 
> Furthermore, in the kernel, you can't use:
> - MMX
> - Floating point
> - KNI or ISSE or 3dNOW.

Tom, could you please explain why we can't use these instructions in kernel
mode ?
I thougth that Linux don't use FP due to performance reasons, but not
because it's not allowed.
RT Linux seems to have some FP restrictions as well, but I think this is
due to the fact that FP instructions could cause exceptions, which might
ruin RT responsiveness by a few usecs.
:-)

> 
> So kernel code will be slower than usermode code.
> 
> > instantaneously become much more enhanced. Besides, since MPEG decoding/encoding
> > cards are popular these days, you begin to see the speed required (so much so
> 
> Please name one that does MPEG _AUDIO_, I don't know one. (I know
> about MPEG video cards...)

Agreed, just provide a standard mpeg library with a well defined API , that
every audio app can use easily.


> 
> Tom

Benno.

Re: MPEG Support

[Thomas Sailer]

sbenno@gardena.net wrote:

> Tom, could you please explain why we can't use these instructions in kernel
> mode ?
> I thougth that Linux don't use FP due to performance reasons, but not
> because it's not allowed.
> RT Linux seems to have some FP restrictions as well, but I think this is
> due to the fact that FP instructions could cause exceptions, which might
> ruin RT responsiveness by a few usecs.
> :-)

Exceptions are one thing, the other is that the kernel doesn't save FPU
state
in the normal case (it does so lazily when switching user space apps).

You could do fsave;fninit by hand, but that would be unportable to other
archs and depending on where you do it would ruin some fast paths
(like lazy FPU switching 8-)). And fsave/frestore is expensive.

Tom

Re: MPEG Support

[Hannu Savolainen]

On Thu, 5 Aug 1999, Kurt Wall wrote:

> The original question I asked was simply if MPEG support had ever been added
> to the <linux/soundcard.h>, as some of the declarations therein seemed to
> suggest that such support would be added.  I didn't ask for a lecture on
> whether or not it is appropriate to add such to the kernel
The define for MPEG audio was added there for cards with hardware MPEG
audio capability. At that time (good old 486 days) software MPEG in kernel
simply was not possible. The definition was added just for future
purposes.

Best regards,

Hannu
-----
Hannu Savolainen (hannu@opensound.com)
http://www.opensound.com (Open Sound System (OSS))
http://www.compusonic.fi (Finnish OSS pages)

Re: MPEG Support

[Dan Hollis]

On Wed, 4 Aug 1999, Jonathan C. Masters wrote:
> Besides, since MPEG decoding/encoding cards are popular these days,

But no vendor will release programming information for any of them.

-Dan