Re: [Audacity-devel] BUG: Audacity and Pulseaudio issue (was: Audacity hangs in Ubuntu pressing space bar many times)

[Al D. <bus...@gm...>]

On Sat, Dec 19, 2009 at 12:36 PM, Luigino Bracci <lb...@gm...> wrote:
>
> 2009/12/19 Al Dimond <bus...@gm...>
>>
>> This is a known bug. ALSA/default on most Linux distros today makes
>> output go through PulseAudio, and there's a deadlock when stopping and
>> starting streams repeatedly somewhere between Audacity, our PortAudio
>> ALSA layer, ALSA's pulse output plugin, and the Pulse client
>> libraries.
>
> Hi Al, Thanks you for your response.
>
> Just a suggestion: What if Audacity opens the connection to Pulseaudio at
> startup, keeps it open all the time, and closes it when Audacity finishes?
> If the problem is opening/closing connections, that can help to keep
> Audacity stable with Pulseaudio.
>

I'd like to do this (both for PulseAudio and JACK). Currently our
audio abstraction layer, PortAudio, doesn't directly support Pulse,
which makes this difficult. Adding Pulse support to PortAudio and a
persistent server connection mode (we certainly don't want a
persistent connection unless it's to a server) to Audacity seems like
a pretty big change to make before 2.0 (I definitely won't be able to
work on it until I'm back home in a week; if the 2.0 timeline is long
it might be worth a shot... I'm just not sure what the plans are
there).

I assume that if I write a Pulse backend for PortAudio it will take a
very long time for it to be adopted upstream, but the changes would be
essentially be isolated, so that would probably be OK.

> As I've explained before, my real problem with Audacity is not hitting
> spacebar too fast. I have six users editing multitrack audio using Audacity
> in Ubuntu 9.04 (they work with 5 or 6 tracks; the tracks have a length of a
> few seconds to a hour). They use Audacity in their full-time job as radio
> producers, but Audacity hangs while editing, at least 4 or 5 times at a day.
> It's hard to trace and reproduce this bug, I just noticed it happens more
> when my users play/stop using spacebar.
>
> I did the hitting-spacebar-many-many-
> many-times thing as a way of reproduce this bug so I can report it here
> easily, but it would be nice to see Audacity without all that inestability.
>
>
>>
>> You'll probably notice that when you use ALSA/hw:0,0 there's a long
>> delay between hitting Play/Record and the stream starting. This is
>> because when you do that Pulse temporarily suspends itself, which
>> takes time. If you really need to use hw:0,0 you should disable
>> PulseAudio temporarily while you do. To do that: open up the
>> PulseAudio volume control applet, click on the "Configuration" tab, and
>> choose the profile "Off" for your sound card. When you're done with
>> Audacity and want the rest of your sound stuff to work again, choose
>> the profile you were using before. But you probably don't really need
>> to use ALSA/hw:0,0 when using Audacity. Just try not to hit the
>> spacebar too fast.
>
> I'm thinking on uninstalling Pulseaudio and use dmix or ESD. What do you
> think is better? I need to get the most stability in Audacity as possible,
> without blocking the sound in other applications; unfortunely, finding
> soundcards in my country with hardware mixing capabilities is near to
> impossible.
>
>>
>> One of these days one of the following will happen, in ascending order
>> of likelihood: (1) I'll figure out what's going on and fix it (2)
>> Someone smarter than me will do it (3) Someone (maybe me) will
>> implement proper libpulse support in PortAudio and it will all go
>> away.
>
> I think that solving this bug is very important for Audacity 2.0; many, many
> people uses Audacity under Ubuntu using cheap hardware, and many of them
> feels that Audacity is very unstable, apparently for the Audacity/Pulseaudio
> issue.
>

I agree... unfortunately it's been really tough to find the bug and
the workaround is a large change.

This was the first I'd heard of people being impacted by this hang in
real-world situations since the transcription slider change... and
then, like clockwork, I ran into it while editing some concert tracks
on Friday.

 - Al