[nSLUG] Audio playback in Rosegarden on ubuntu lucid

Herb htheriault at gmail.com
Wed Sep 7 11:57:58 ADT 2011


There should be a module for jackd to play nice with that vile
creature that is pulseaudio. Here's how the Arch Linux deals with it,
if that's any help.

https://wiki.archlinux.org/index.php/PulseAudio#PulseAudio_through_JACK_the_new_way

I always drop into openbox whenever I'm doing anything with audio /
video ( Ardour / xJadeo, Kdenlive) It's just alsa at that point. Much
easier to deal with and no overhead to speak of.

Herb

On Wed, Sep 7, 2011 at 11:47 AM, Dop Ganger <nslug at fop.ns.ca> wrote:
> On Wed, 7 Sep 2011, Ryan Neily wrote:
>
>> To install and run Rosegarden requires jackd.
>> I installed and got jackd running with the assistance of readily found
>> documentation.
>
> [...]
>
>> Rosegarden worked fine except it would not play back the sound. Definitely
>> an obstacle to happiness.
>
> Ubuntu has pulseaudio installed by default, did you take care of that first?
> You may need to remove it and reconfigure all sorts of odds and ends to cope
> with that. My guess is jackd is trying to output to a sound card that is
> held open by pulseaudio.
>
>> Fire up Synaptic and install a realtime kernel. Rosegarden requires a
>> default 1000HZ setting instead of the now default 250HZ to be fast
>> enough to process a midi file. The pre-emptive RT kernel is set to the
>> required 1000HZ.
>
> Just curious, what processing of a midi file requires 1000HZ? I remember
> playing midis on my AWE32 on a 486 without any issue at all.
>
> You might also want to tinker with /proc/sys/kernel/sched*ns to alter the
> latency to boost foreground processes, depending on your workload. I have a
> bug I've been trying to isolate for a while that causes video skips in
> mplayer (audio plays fine, oddly); winching the ns down by orders of
> magnitude makes a vast improvement.
>
> Tuning the readahead with blockdev made a difference for me as well. The
> default is 256k which is excessively small for most devices these days,
> considering the mplayer cache is by default 8 meg. I found a hot spot on my
> system going from filesystem -> LVM -> RAID1 -> disk where almost every
> request was going through in 256k chunks. Ramping them up to 2 meg made a
> big difference in the number of accesses (and thus context switches), and I
> set the RAID1 and disk readahead caches to 4 meg.
>
>> The above script starts by killing off all the apps in the chain so as
>> to have a clean slate. Jackd has to be finished firing up and listening
>> when Timidity starts for example. The parameters need to be set. -iA
>> ( Input alsa ) -B2,8 (2 channels 8 bit) -Oj (output jackd). With the
>> supporting applications running it is time to open Rosegarden.
>
> You might want to use ionice, schedtool and renice to boost the IO priority,
> CPU priority and process priority to start apps, or change them on the fly
> as desired.
>
> Cheers... Dop.
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