[pulseaudio-tickets] [Bug 42804] raop module does not work with shairport

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=42804

--- Comment #30 from Matthias <pulseaudio at niafc.de> ---
(In reply to comment #28)
> I've been testing my code using VLC, and it worked reasonably well so far.
> Today I tested Rhythmbox and found that the sound quality was terrible.
> (Very rough sound). This difference is observed even for the same mp4 file.
> I have so far no clue about what's going on, but will continue to
> investigate this issue.

Hi Hajime,

I'm back from my vacation - the first thing I did when I entered my home was to
boot up my laptop and compile your version of pulseaudio :).

First of all, congratulations and thanks for the great job. Second: I also
encountered your "rough sound" issue when playing music with 'banshee'. Reading
your entry here I wondered what that expression meant, but I can't think of a
better description. Sounds like my Minx Air turned into a 20$ bluetooth speark
;).

I used to test my patches with 'banshee' (as it's preinstalled with ubuntu
12.04) and 'gst123'. I also used 'banshee' to test your version of the raop
module - which resulted in the "rough sound" described above.

Today I merged my work on ALAC encoding into your branch. The sound distortion
(using banshee) is gone now. I confirmed that using my Minx Air using RSA
encryption and without encryption (by commenting out encryption in
raop_client.c).

That leaves me at a point where I don't want to be: This is not a programming,
but a license issue. As pointed out in the ALAC trac [1], the license of the
ALAC codec part is ambiguous (Apple Licence vs. Apache V2.0).

Though, as I already wrote: Timothy Gu created a debian package of Apple's (tm)
ALAC library [2]. I used his library to create a simple encoder library [3].
My patch - as the time of writing it's incomplete and more a proof of concept -
uses these libraries (read: libsalac which in turn uses libalac).

I'm not sure if this "library use" could affect the license of any software
that uses libsalac or libalac. Any software license laywers here ;)?

So, back to the technical discussion: It sounds to me (pun intended) as if the
"rough sound issue" can be resolved using "true" ALAC encoding - and in turn,
that present "encoding" does not work correctly in some situations. I've got no
idea why this should affect rhythmbox, gst123 and banshee but not vlc (wild
guess: are rhythmbox, gst123 and banshee built with gstreamer support?).

I did a packet dump of some playback with your branch and libsalac. It shows
series of retransmit requests. I am currently working on a packet retransmit
buffer implementation.

Until then, please find attached a patch for libsalac to Hajime's branch.
Works for me with my Minx Air. As the license issue is still unresolved, this
is just a proof-of-concept patch and should not be included in any software
distribution whatsoever as I do not want to be hunted by Apple's (tm) laywers.

[1]: Bug #3 http://alac.macosforge.org/trac/ticket/3
[2]: Timothy Gu's LibALAC: https://github.com/TimothyGu/alac
[3]: LibSALAC: http://repo.or.cz/w/libsalac.git

Greetings,

Matthias

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