Hi Max,
2009/3/23 Max Kellermann m...@duempel.org:
On 2009/03/22 11:43, Kodest kod...@gmail.com wrote:
Just tell me when i can check the wakeups again :)
Submit a bug report, we'll add it to the 0.15 roadmap.
http://musicpd.org/mantis/view.php?id=2183
Is there any docs on how the output mechanism works? I would be
interested in how the audio chunks travel among the different
threads at the output subsystem, but the code is quite
complex. Maybe I can help if i understand this one. (Only maybe
because my time is really limited nowadays.)
Yes, I've been missing your regular contributions in the past months
;)
Basically: the decoder thread feeds music_chunk objects into a
music_pipe. The player thread takes them from there, and appends them
to the output's music_pipe instance. The output threads now consume
them. When all output threads have consumed a music_chunk, it is
freed (returned to the music_buffer).
The frequent wakeups (supposedly) come from the threads waiting for
more chunks, or waiting for enough room in the pipe, or waiting for
free chunks in the music_buffer. They're just using g_usleep(10ms) to
synchronize, because I havn't had time to think about the proper
solution yet (using GCond or struct notify).
For most setups (small buffers, low latency), the
music_pipe/chunk/buffer code is more efficient than the old method
(fully synchronous buffer passing), but for your setup, it's worse.
We will optimize MPD for all possible use cases.
I tried with default sized alsa buffer (period_size=1024; buffer_size=8192).
I get the same amount of wakeups caused by mpd (~950 per sec).
Only the number of interrupts changed to 50 per sec from 10.
Btw low latency can be achieved through large buffers as well; this
could be useful reading:
http://0pointer.de/blog/projects/pulse-glitch-free.html
I believe it'll take some time to fully understand that code, so if
you have little time, I promise to fix it this week.
Thanks for the info, I will look at that code too.
Regards,
Kodest
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