On 04/29/2013 12:18 PM, Tanu Kaskinen wrote:
On Fri, 2013-04-26 at 16:40 +0200, David Henningsson wrote:
On 04/26/2013 03:37 PM, Tanu Kaskinen wrote:
On Fri, 2013-04-26 at 14:54 +0200, David Henningsson wrote:
On 04/26/2013 12:48 PM, Tanu Kaskinen wrote:
On Fri, 2013-04-26 at 05:05 +0200, Alexander Couzens wrote:
Hello,
I would like to work on pulseaudio as gsoc student this year.
Can you give me some feedback about my ideas, please?
I'm working with pulse for a while and this is how I'm using it:
-1-
We have an announcements system at c-base my local hackerspace.
It's a multi speaker setup based on OpenWrt and Ubuntu.
- sender is a Ubuntu x86 system. it plays hourly time announcement +
samples
- receivers are mips32 based routers, arm systems, x86
This system announce every hour. Got a tts + jsonrpc interface to play
soundfiles.
The receiver disappear from time to time. (module-tunnel-sink lacks a
reconnect feature).
Also in future this setup should support playing sounds on a random
group of speakers.
-2-
I'm using it at home
- remote home system: speakers connected to 1 pulseaudio server +
laptop as sender
|- receiver announce themself via avahi/bonjour
|- sender: laptop use them as sink
Pulseaudio should recognize your environment (how? or let the user
choose which environment-profile apply).
Different locations, different audio setup. At work you want to move
only mplayer/vlc/.. stream to
the remote sink. At home, maybe you want to move all streams over to a
good amplifier.
Playing video doesn't work reliable. Playing soundfiles works better,
but not perfect.
My ideas for a gsoc application:
- Fix network sinks. Try to move a stream to network sink and back
moments later it will run into problems.
e.g. mplayer just stop playing and hang. My job would be
additional testing and fixing upcoming bugs in pulseaudio.
Making module-tunnel-sink reliable would be very welcome. Estimating the
amount of work is hard, though, when you don't know what exactly are the
root causes for the bugs, which makes writing the project plan hard too.
I'd like to see a rewrite of module-tunnel-sink to use the libpulse API
instead of doing the protocol stuff directly.
+1
...and in extension, perhaps a module-tunnel-detect that would load the
same amount of module-tunnel-cards, module-tunnel-sinks and
module-tunnel-sources as are present on the remote instance. But that is
just a wild idea at the moment.
I agree that this would be good. We don't currently have
module-tunnel-card, but we should. module-zeroconf-detect is already
used for detecting remote stuff, so I don't know if we need any new
module-tunnel-detect module.
Sure, if module-zeroconf-detect can be configured to follow a specific
server, that would work. I haven't investigated the zeroconf stuff much.
I also think that wifi + TCP + low latency is a very hard thing to
achieve reliably. The question is if it is possible at all, and if not,
what the options are. Arun didn't seem very happy about improving RTP
support in PulseAudio.
At least one option should be to not insist on low latency (IIRC the
latency is now hardcoded to 150 ms). Streaming music over wifi has no
need for low latency.
I tried to google a bit for how long latency Wifi really has, and at
least this [1] link points to a second or two not being too unusual.
And seconds of latency is an annoyance even over Wifi.
Sure, but I think it would still be in many cases better than occasional
drop-outs. To me TCP seems better than UDP for raw PCM data in pretty
much all cases, except when there is a hard requirement for an upper
limit in latency.
I admit that I don't know much about network latency, but my impression
is that we have different people who every now and then drop into our
IRC channel asking why there are several seconds of latency for a simple
network connection, and they are not happy with it.
- authentication - add password based authentication. it can be either
a password or a password to add your cookie to the authorized_cookies.
Also a request + response system would be good. Implement it as popup
Authentication without encryption is very questionable security-wise.
Perhaps it's still useful, though? I would presume that in many cases
it's sufficient that it's not trivial for any random person to gain
access to the server and mess with things. The current cookie-based
authentication isn't any more secure anyway, so a password-based
authentication would just be a more convenient way to achieve roughly
the same level of security.
We could also discuss how to add encryption support to PulseAudio.
Somebody last year tried something popup-like, but it's not easy trying
to get that right with all Desktop Environments.
I'm not seeing the use case for having PulseAudio handle passwords. Can
somebody enlighten me?
I'd imagine it's easier (or at least more intuitive) to run "pactl
set-password-for-remote-clients correcthorsebatterystaple" on a sound
server machine and then type the password to a prompt when connecting
the first time from each client machine, than to figure out and remember
that the cookie file needs to be copied to each client machine, after
the connection is failing with "Access denied".
Right. Then it sounds like an encrypted connection would make more
sense, e g an ssh tunnel that would already cover for both passwords,
keys and what not. However, if that means an additional ssh library to
depend on...
Can you clarify your position? It sounds like you're arguing for two
things:
* We should not implement password support before encryption support,
because they may not be completely orthogonal. For example, if we choose
SSH tunnels as the encryption solution, we may get password
authentication for free (I have doubts about that, but I don't know the
capabilities of SSH well enough to argue).
* We should never implement encryption, because that introduces a
dependency on a crypto library (implementing crypto ourselves is out of
question, I think we can agree that much).
Those two statements are in conflict: if we will never implement
encryption, it doesn't make sense to argue that password authentication
should wait for encryption support. I probably misunderstood you.
Well; having given this a second or two of thought, I think the best
option would be if we had existing support outside PulseAudio. SSH
tunnels can be made by ssh without explicit support within PulseAudio.
It is also something long wanted to have ssh forwarding of the
PulseAudio protocol, just like the X protocol.
That would be my preferred option. If that is not possible, I think
having an optional dependency on a crypto library would be second best,
even if I don't like new dependencies.
--
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic
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