Subject: Re: [linux-audio-dev] [ANN] AlsaPlayer 0.99.52-cvs20011126-jack
From: Paul Davis (pbd_AT_Op.Net)
Date: Tue Nov 27 2001 - 22:37:29 EET
>Could you try the above with a single CPU kernel??
i don't have one. there is some boot-time magic to ignore multiple
processors, but i don't remember what it is. anybody?
>I will hack jackd tonight to do only Output.
you mean the alsa-driver. they are separate pieces of code with no
explicit connection. this needs to be remembered at all times.
>The process() call is in app/AlsaNode.cpp, the code looks allright to
>me, but I have only simple_client to compare it to :)
as i've mentioned in private email, i've done a lot of debugging
today. i can't find anything that explains the noise. its definitely
not clipping, at least not at the jack-stage of things. if it is
clipping, its way back at the disk i/o level, and somehow only shows
up because of the float output ...
>Sometimes an overrun will cause massive corruption with the sound, only
>fixable by quitting and restarting jackd. I.e. quitting jackplayer and
>reconnecting will still produce garbled sound. This happens because the
>frequency of the process() calls gets erratic. Jackd will also segfault
>randomly once it is in this state. I can't seem to use GDB to trace the
>crash. I'll try connecting GDB to a running jackd next.
i wouldn't bother. i've found and fixed several critical errors on
jackd during the day today.
>> the effect is strange. its not like harsh clipping. its a strange kind
>> of constant buzzing, but its definitely like clipping in that its
>> clearly signal level related.
>
>Yes, I can get rid of pops by lowering the volume of jackplayer (need
>GTK+ GUI for this). But this suggest the clipping problem is inside
>jackd.
the effect i get is not "pops". its a strange metallic shimmer that
kicks in a louder power levels.
>calles where nframes is 1. I did some statistics over 5000 calls for 64
>frames per interrupt. Roughly 45% of the calls are with nframes around
>64, another 45% around 1, the remaining % is evenly distributed inbetween thes
>e 2 values. Doesn't this make it very inefficient?
yes, this is a bug/misdesign in ALSA. i've added code to avoid it in
the alsa-driver for JACK.
--p
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