Subject: Re: [ecasound] clicking
From: Kai Vehmanen (k_AT_eca.cx)
Date: Wed Oct 10 2001 - 01:57:05 EEST
On Fri, 17 Aug 2001, kelly george hirai wrote:
> i reciently upgraded to the 2.0.2 ecasound from 1.9.4 because i've
> been getting a clicking on the output of my playback file only when i do
> duplex recording (recording with playback). it doesn't effect the
> recording but is annoying. 2.0.2 didn't seem to help this problem. also,
This sounds like a driver problem. You might want to try a different set
of drivers (ALSA, OSS/comm, etc), or just upgrading to a later version.
> after i upgraded to the 2.0.2, i'm getting my input signal from /dev/dsp1
> comming out of the pcm channel of my sound card. with 1.9.4, i was only
> getting the line-thru, and thus no latency on the performance i was
> currently recording. i wonder what happend.
Enabling line-in monitoring is a mixer feature. Ecasound doesn't touch
any mixer settings, so problem is probably elsewhere.
> also, is there a way to have my tracks loaded into memory, record to
> memory and hold off on the disk writing until recording is done or maybe
> write to disk on comand?
Actually yes, but only for reading files. Ecasound has a separate mmap()
mode for .wav and .raw access. This is not a very well known feature,
although it's quite old. At the time it was implemented, SCHED_FIFO+mmap()
-based streaming was the hot topic of the day on linux-audio-dev. :)
Anyway, to enable mmap():
ecasound -i somefile.wav,1 -o /dev/dsp
... and that's it. Ecasound mmap()'s the whole file and kernel takes care
of copying data from disk to memory (on-demand). Ecasound just accesses
the file as if it was completely in memory.
Implementing this for wav and raw output shouldn't be too hard, but there
hasn't been much use for this feature. Using -z:db solves most disk i/o
performance problems and scales better for streaming large amounts of
data.
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