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Is 'libao' useful/desirable? [ANSWERED]
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dufeu
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PostPosted: Sun Jul 22, 2012 12:40 am    Post subject: Is 'libao' useful/desirable? [ANSWERED] Reply with quote

I'm building/re-purposing an Intel Atom based system (netbook) from 3rd stage install and I want to be sure the USE flags I set are reasonable.

In this instance, I see the 'ao' USE flag is not part of the standard profile I selected:
Code:
default/linux/x86/10.0/desktop/kde *

As I read the description on xiph.org, libao takes a sound stream which a program wants to play and outputs it into a single format suitable for whatever your sound stack expects.

Do I understand libao's function correctly and is libao actually useful? I've been under the impression that software like 'pulseaudio' and 'phonon' already performed this type of function.

Edit: And the ANSWER is -

I appreciate the answers and they led me in the right direction for what I needed to know.

With the clue of 'sox', I was able to look with more insight at systems where I have 'libao' present. On these systems, it turns out that libao was called in at the behest of 'k3b' only. This is because of my policy to turn on nearly all k3b USE flags on these systems in order to be sure of handling just about any CD/DVD/CVD task that may come up.

Unless you purchase a USB 2.0 connected external CD/DVD/RW drive, k3b is completely pointless for all Atom based netbooks. Since Atoms are used virtually only in netbooks, 'libao' is not useful nor desired for any Atom based computer.

Based on my further reading, 'libao' is not really useful nor desired anywhere. i.e. Those packages that can make use of it all appear to have alternatives for accomplishing the same thing. The only real reason to include 'libao' for most people would appear to be as an alternative library if they're dissatisfied with the provided library a given package uses. At this point, I'll probably turn off USE='ao' on all my systems.

Thanks for the good answers!
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Last edited by dufeu on Tue Jul 31, 2012 3:57 pm; edited 2 times in total
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VinzC
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PostPosted: Mon Jul 23, 2012 12:46 pm    Post subject: Reply with quote

On my system only sox depends on libao, which has been included BTW. So I guess it's a question whether you need sox or not I guess?
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khayyam
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PostPosted: Tue Jul 24, 2012 4:14 pm    Post subject: Reply with quote

dufeu ...

the only pacakges, besides sox, I can think of that might use libao are media-sound/vorbis-tools if the ogg123 useflag is enabled, and media-sound/cmus which works perfectly fine without it.

So, its not widely used, but as VincZ said, it depends on what particular functionality you need.

best ... khay
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dufeu
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PostPosted: Tue Jul 31, 2012 4:11 pm    Post subject: Reply with quote

Finally, I don't consider these kinds of questions/answers to be complete without context. To that end for the systems where I have 'libao' enabled, the following should make it clear where I might possibly use it:
Code:
# USE="-ao" emerge -pNDv @world

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild   R    ] net-misc/rdesktop-1.7.1  USE="alsa ipv6 libsamplerate -ao* -debug -oss -pcsc-lite" 0 kB
[ebuild   R    ] media-sound/sox-14.4.0  USE="alsa amr encode ffmpeg flac id3tag mad ogg openmp png pulseaudio sndfile wavpack -ao* -debug -ladspa -oss -static-libs -twolame" 0 kB

Total: 2 packages (2 reinstalls), Size of downloads: 0 kB

# equery d sox && equery d rdesktop
 * These packages depend on sox:
app-cdr/k3b-2.0.2-r3 (sox ? media-sound/sox)
 * These packages depend on rdesktop:
kde-base/krdc-4.8.4 (rdesktop ? net-misc/rdesktop)

For me, in other words, 'ao' is not really needed for anything anywhere.
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Last edited by dufeu on Wed Aug 01, 2012 5:33 pm; edited 1 time in total
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VinzC
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PostPosted: Tue Jul 31, 2012 5:49 pm    Post subject: Reply with quote

Thank you very much for your deep investigation, dufeu.
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