I've managed to narrow down the problem with ladspa plugins. Since it used to work, but doesn't any more I figured if I could find the specific change I would be able to get an idea where to look to fix the problem. I checked out 20 some CVS versions, built and patched them as necessary to get things working and found that the ladspa plugins were broken on 2/4/2003. CVS of 2003-02-04 at midnight worked, but CVS of 2003-02-05 didn't. After diffing and then replacing new code with old on a change by change basis, I found that snd_pcm_plugin_mmap() and snd_pcm_plugin_munmap() in alsa-lib/src/pcm/pcm_plugin.c were stubbed out and marked ATTRIBUTE_UNUSED (aparently durring some of perex's DMix plugin changes). Problem is, pcm_ladspa.c and others seem to still use these functions. Adding these functions back into my checked out cvs 2/5/2003 version and ladspa plugins magically start working again.
But, alas, things are not this easy. I took my src copy of the 0.9.6 release (I can't seem to get a current CVS to compile, it complains about a missing alsa-lib/src/userfile.c file) and put the functions back in (added the meat and removed the attribute), compiled and tested. I now get sound out but it's all garbled.
After looking a bit at pcm_ladspa.c and doing a few greps I found or infered that:
1. many of the pcm_{plugintype file here}.c files in there snd_pcm_ops_t structure variable they set the mmap and munmap fields still use this "ATTRIBUTE_UNUSED" function. Line 710 in pcm_ladspa.c.
2. DMix uses it's own version of these functions.
3. I'm infering that since just putting this function back in doesn't work, that something fundamental has changed with the mmap implmentation that makes it so the old functions don't work.
I'm guessing that sometime since Feb., there's been some archetectural changes to some of the plugin stuff to get DMix working. But, the other portions, including ladspa support, haven't kept up with the changes made and so are broken (am I the ONLY person trying to get ladspa plugins working with Alsa?). I'd like to get this fixed. I'm perfectly happy to do the work myself, but I don't know enough of how Alsa works in order to get this done.
Here's what I understand: I'm getting the idea that each plugin type, when it is parsed in the config file, gets setup. I presume that the _snd_pcm_ladspa_open() function is the entry point for the ladspa stuff. It opens and does some stuff then it uses the snd_pcm_ops_t structure to tell the pcm stuff what functions to call in order to get things done when working with this plugin. Kinda a OOP without C++ concept with the pcm_ladspa.c module as the "ladspa plugin handler object". Origionally it seems that the pcm_plugin.c module was to provide the basic functionality for all the plugins, and then pcm_ladspa.c could override or use those functions in it's snd_pcm_ops_t as it needed to.
So, if I was to fix this, I see two potential courses of action:
1. I can put meat back into the snd_pcm_plugin_mmap() ..._munmap() functions and then fix it to make it work with the newer stuff so that I both get sound out and it comes out properly.
2. I can create my own snd_pcm_ladspa_mmap() and ..._munmap() functions and use those.
In either situation, I don't have a clue what I need to put in these functions to make them work. Or even how they really fit into the structure of how things work with the pcm system. I don't know enough about Alsa internals to hack this easily (though I'm finding I'm quickly being forced to learn).
So, can someone either fix this for me
or,
please educate me enough on what I need to do to make this work so I can fix it myself and give you guys a patch.
Help, please!?!?
Thanks, - Steve
Steve deRosier wrote:
All,
I hope that someone here can help with a problem we're having with the newer versions of the alsa-lib. We are using the ladspa interface with alsa to use a pitch-shifting plugin. It worked fine with earlier versions of the alsa lib, but with the newer versions it produces no sound output. The last version of alsa that we know works (and is the "stable" version we're using in our system at the moment because of it) is 0.9.0rc6. Shortly after this version, the ladspa stuff was broken (segfault, see the thread starting with:
http://www.mail-archive.com/[EMAIL PROTECTED]/msg07847.html
). The segfault was fixed, but we've not been able to get audio out of alsa-lib when using the plugin since.
I've been trying to track this down, but I'm out of ideas of what/where to fiddle with. We really want to move to more current versions of alsa, as working with out-of-date versions is causing us other headaches, but we can't till we fix this problem.
One interesting thing...alsa uses an older version of the ladspa.h header. Replaced w/ a more current version and no change though.
I've played with our configuration in asound.conf and no joy. I've examined the code in src/pcm/pcm_ladspa.c and nothing pops up at me. I'm currently looking at the source for the plugin, but nothing obvious is showing itself.
I'd be happy to fix this myself (or get a patch from someone), but I'm out of ideas of where to look or even how to go about debugging this particular problem. Maybe it's a configuration problem; Maybe a problem with pcm_ladspa.c; Maybe a problem with something else that just happened to change around that time. Any ideas of where I can look or how I can debug this issue?
Last known working version: 0.9.0rc6
Currently working with: 0.9.6 and a cvs snapshot from last Thursday (broken in both)
Plugin is from: http://plugin.org.uk/releases/0.4.2/
In our snd_pcm_open call, our device is: "plug:pd"
The plugin we're using is: /lib/ladspa/am_pitchshift_1433.so
our asound.conf file looks like: pcm.pd { type ladspa slave.pcm "plughw:0,0" path "/lib/ladspa" plugins [ { label amPitchshift input { controls [ 1.189207 3 ] } } ] }
Thanks, - Steve
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