Use of _hint() functions and older machines

Use of _hint() functions and older machines

[Randell Jesup]

[ I initially posted this to the -users list, but it may be more 
appropriate here ]

At Mozilla, we're in the process of adding support for WebRTC 
(http://webrtc.org/), which is being standardized by the IETF (their 
part is 'rtcweb'), and the W3C.  This adds real-time audio and video 
(and data) communication to browsers, peer-to-peer over encrypted channels.

We have a sound library that can load either Pulse or Alsa.  However, 
for Alsa, it wants to look at snd_device_name_hint() and also 
_get_hint() and _free_hint().  It lazy-binds to libasound, so it will 
dlopen() it and then dlsym() all the symbols it uses; if any fail it 
unloads the lib and says it's not there.  It  uses the hint functions to 
build a device list, for example for presenting to the user.

I have two problems:

1) Firefox is build on machines configured with I believe Centos5, and 
I'm told the machines run Alsa 1.0.12, while the hints() functions were 
added in 1.0.14 (released June 2007).  Right now I can't build release 
or 'try' builds on the build servers because of this.

2) We'd like to run on older machines if possible, and official release 
builds are made on those servers.  On older machines, _hint() aren't 
available, so even if I make them optional to dlsym-loading, I would 
need some other method to get the information I assume using older, 
now-deprecated-or-gone interfaces.

Any suggestions?  Tips?

See 
http://code.google.com/p/webrtc/source/browse/trunk/src/modules/audio_device/main/source/linux/audio_device_alsa_linux.cc?r=347#2348 
for how they're used currently.

Thanks!

-- 
Randell Jesup
randell-ietf@jesup.org

Re: Use of _hint() functions and older machines

[Colin Guthrie]

'Twas brillig, and Randell Jesup at 21/10/11 04:28 did gyre and gimble:
> [ I initially posted this to the -users list, but it may be more 
> appropriate here ]
> 
> At Mozilla, we're in the process of adding support for WebRTC 
> (http://webrtc.org/), which is being standardized by the IETF (their 
> part is 'rtcweb'), and the W3C.  This adds real-time audio and video 
> (and data) communication to browsers, peer-to-peer over encrypted channels.
> 
> We have a sound library that can load either Pulse or Alsa.  However, 
> for Alsa, it wants to look at snd_device_name_hint() and also 
> _get_hint() and _free_hint().  It lazy-binds to libasound, so it will 
> dlopen() it and then dlsym() all the symbols it uses; if any fail it 
> unloads the lib and says it's not there.  It  uses the hint functions to 
> build a device list, for example for presenting to the user.
> 
> I have two problems:
> 
> 1) Firefox is build on machines configured with I believe Centos5, and 
> I'm told the machines run Alsa 1.0.12, while the hints() functions were 
> added in 1.0.14 (released June 2007).  Right now I can't build release 
> or 'try' builds on the build servers because of this.

Are you sure? CentOS 5 is fairly new and on a box I have access to:

[csuk@shake ~]$ cat /etc/redhat-release
CentOS release 5.5 (Final)
[csuk@shake ~]$ rpm -q alsa-lib
alsa-lib-1.0.17-1.el5


So I guess it's likely CentOS 4? Even still updating alsa-lib to 1.0.14
should be pretty trivial and safe. Or do you not have any control at all
over the version used?

> 2) We'd like to run on older machines if possible, and official release 
> builds are made on those servers.  On older machines, _hint() aren't 
> available, so even if I make them optional to dlsym-loading, I would 
> need some other method to get the information I assume using older, 
> now-deprecated-or-gone interfaces.

Not sure, but I suspect strongly that you should simply not worry about
this too much. While it's nice to give a good experience to everyone,
people with systems 4 years old have got to expect a degree of
degradation over a more recent install.

My €0.02

Col

-- 

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

Day Job:
  Tribalogic Limited http://www.tribalogic.net/
Open Source:
  Mageia Contributor http://www.mageia.org/
  PulseAudio Hacker http://www.pulseaudio.org/
  Trac Hacker http://trac.edgewall.org/
_______________________________________________
Alsa-devel mailing list
Alsa-devel@alsa-project.org
http://mailman.alsa-project.org/mailman/listinfo/alsa-devel

Re: Use of _hint() functions and older machines

[Randell Jesup]

On 10/22/2011 2:04 PM, Colin Guthrie wrote:
> 'Twas brillig, and Randell Jesup at 21/10/11 04:28 did gyre and gimble:
>> [ I initially posted this to the -users list, but it may be more
>> appropriate here ]
>>
>> At Mozilla, we're in the process of adding support for WebRTC
>> (http://webrtc.org/), which is being standardized by the IETF (their
>> part is 'rtcweb'), and the W3C.  This adds real-time audio and video
>> (and data) communication to browsers, peer-to-peer over encrypted channels.
>>
>> We have a sound library that can load either Pulse or Alsa.  However,
>> for Alsa, it wants to look at snd_device_name_hint() and also
>> _get_hint() and _free_hint().  It lazy-binds to libasound, so it will
>> dlopen() it and then dlsym() all the symbols it uses; if any fail it
>> unloads the lib and says it's not there.  It  uses the hint functions to
>> build a device list, for example for presenting to the user.
>>
>> I have two problems:
>>
>> 1) Firefox is build on machines configured with I believe Centos5, and
>> I'm told the machines run Alsa 1.0.12, while the hints() functions were
>> added in 1.0.14 (released June 2007).  Right now I can't build release
>> or 'try' builds on the build servers because of this.
>
> Are you sure? CentOS 5 is fairly new and on a box I have access to:
>
> [csuk@shake ~]$ cat /etc/redhat-release
> CentOS release 5.5 (Final)
> [csuk@shake ~]$ rpm -q alsa-lib
> alsa-lib-1.0.17-1.el5
>
>
> So I guess it's likely CentOS 4? Even still updating alsa-lib to 1.0.14
> should be pretty trivial and safe. Or do you not have any control at all
> over the version used?

In general no, I do not have any control.  These are the 'hive' of build 
and 'try' servers used at Mozilla; they run a "least-common-denominator" 
set of packages so that we don't accidentally introduce a dependency on 
a newer version.  With 400+ million users, we need to be careful about 
this.  (I don't know how many of those are Linux, but it's still a 
substantial number.)

Also, the point here is we need to package a binary that will operate on 
the minimum configuration we support.  10.1.14 was released initially 
just over 4 years ago; I don't know when it got into distro releases, 
but one would assume that would have occurred over the next 6 months to 
a year, so users who installed more than 3-4 years ago might have 
versions before .14, depending on if they installed updates.

>> 2) We'd like to run on older machines if possible, and official release
>> builds are made on those servers.  On older machines, _hint() aren't
>> available, so even if I make them optional to dlsym-loading, I would
>> need some other method to get the information I assume using older,
>> now-deprecated-or-gone interfaces.
>
> Not sure, but I suspect strongly that you should simply not worry about
> this too much. While it's nice to give a good experience to everyone,
> people with systems 4 years old have got to expect a degree of
> degradation over a more recent install.

I understand, and I can try to make an argument for bumping the minimum 
configuration required - and that might fly.  But I need to know what 
the alternative is to even make the argument for bumping.

Thanks for the reply!


-- 
Randell Jesup
randell-ietf@jesup.org

Re: Use of _hint() functions and older machines

[Clemens Ladisch]

On 10/21/2011 05:28 AM, Randell Jesup wrote:
> On older machines, _hint() aren't available, so even if I make them
> optional to dlsym-loading, I would need some other method to get the
> information I assume using older, now-deprecated-or-gone interfaces.

On older machines, that information wasn't available at all.

The recommendation was to use "default" or to let the user enter
a device name.

The best way to get a list of devices would have been to enumerate sound
cards with snd_card_next(), then use device names "default:CARD=x".
However, this gets only the primary device of each card, there might be
sound cards without a PCM device, devices not based on an ALSA kernel
driver aren't listed, and the "default:CARD=x" mechanism doesn't work if
the user has redefined the "default" device.


Regards,
Clemens

Re: Use of _hint() functions and older machines

[Randell Jesup]

On 10/23/2011 6:36 AM, Clemens Ladisch wrote:
> On 10/21/2011 05:28 AM, Randell Jesup wrote:
>> On older machines, _hint() aren't available, so even if I make them
>> optional to dlsym-loading, I would need some other method to get the
>> information I assume using older, now-deprecated-or-gone interfaces.
>
> On older machines, that information wasn't available at all.
>
> The recommendation was to use "default" or to let the user enter
> a device name.

Ah.  Ok.  Wow, was it really that painful?  I didn't do a lot of Linux 
media stuff back then, and generally had only built-in-audio (no USB 
headsets, etc) with simple speakers.

> The best way to get a list of devices would have been to enumerate sound
> cards with snd_card_next(), then use device names "default:CARD=x".
> However, this gets only the primary device of each card, there might be
> sound cards without a PCM device, devices not based on an ALSA kernel
> driver aren't listed, and the "default:CARD=x" mechanism doesn't work if
> the user has redefined the "default" device.

Ugh.  So, there's no reasonable way to get a user-understandable list 
before .14?  How useful was 
snd_ctl_card_info_get_name()/snd_ctl_card_info()?  And I guess I'd need 
to enumerate the 'devices' and 'subdevices' on each card as well...

Thanks for the info, BTW

-- 
Randell Jesup
randell-ietf@jesup.org

Re: Use of _hint() functions and older machines

[Raymond Yau]

2011/10/24 Randell Jesup <randell1@jesup.org>:
> On 10/23/2011 6:36 AM, Clemens Ladisch wrote:
>> On 10/21/2011 05:28 AM, Randell Jesup wrote:
>>> On older machines, _hint() aren't available, so even if I make them
>>> optional to dlsym-loading, I would need some other method to get the
>>> information I assume using older, now-deprecated-or-gone interfaces.
>>
>> On older machines, that information wasn't available at all.
>>
>> The recommendation was to use "default" or to let the user enter
>> a device name.
>
> Ah.  Ok.  Wow, was it really that painful?  I didn't do a lot of Linux
> media stuff back then, and generally had only built-in-audio (no USB
> headsets, etc) with simple speakers.

Those rack servers which are running 7x24 non-stop inside data center,
does not have any on-board audio,

Re: Use of _hint() functions and older machines

[Clemens Ladisch]

Randell Jesup wrote:
> On 10/23/2011 6:36 AM, Clemens Ladisch wrote:
> > The best way to get a list of devices would have been to enumerate sound
> > cards with snd_card_next(), then use device names "default:CARD=x".
> > However, this gets only the primary device of each card, there might be
> > sound cards without a PCM device, devices not based on an ALSA kernel
> > driver aren't listed, and the "default:CARD=x" mechanism doesn't work if
> > the user has redefined the "default" device.
> 
> Ugh.  So, there's no reasonable way to get a user-understandable list
> before .14?  How useful was snd_ctl_card_info_get_name()?

That gives you the card name, which is not the same as the name of the
PCM device (although it shouldn't matter when the card has only one
PCM device).

> And I guess I'd need to enumerate the 'devices' and 'subdevices' on
> each card as well...

Yes, but subdevices are typically used for multiple streams that are
mixed together, so you can ignore them.


Regards,
Clemens