stereo delay plugin for ladspa

My latest music player project has an special demand which require to delay one channel of stereo a little than another, the supposedly applied scene is that listener is not sitting in the middle of speakers, As we all know sound also need time to arrive
the target,here your ear, since the distance between user and two speaks is different, theoretically user should has a bad music experience, in fact in most conditions the different is so little that ears can't discern it. But don't we should have an attractable
point . so do it. from point of technique, the process is really simple, buffer one channel till the wanted time reached. I thought there should be ready open source code can be used, it really does after search on the yahoo. ladspa has a lot of plugin and
can do almost everything you want to hack your audio. after try all the delay plugin integrated into that project, I have to say these plugins is really powerful but can't act what I want, all of them use complicated algorithm to achieve functions far more
what I needed. so I write my own , it is very simple but really work, the code is listed here for you refer.

Insert attached code into 'lcr_delay_1436.xml', between ' ]]></callback>' and '</ladspa>' and recompile the whole ladspa plugin.

usage:

for alsa user, the asound.conf should look like this:

pcm.ladspa {

type ladspa

slave.pcm "plughw:0,0";

path "/usr/lib/ladspa";

plugins [{

label lrDelay

id 1437

input {

controls [ 1000 2 ]

}

}]

}

pcm.!default{

type plug

slave.pcm ladspa

}

meaning of the controls parameters:

first one: delay time (ms) , range of value between 1 to 2700

second: channel you want to delay. 1 left,2 right.

code:

<plugin label="lrDelay" id="1437" class="DelayPlugin">

<name>L/R Delay</name>

<p>This is a very simple left/right delay .</p>

<callback event="instantiate"><![CDATA[

buffer_size = 32768;

buffer_offset=0;

fs = s_rate;

// printf("s_rate=%d\n",s_rate);

while (buffer_size < fs * 2.7f) {

buffer_size *= 2;

}

buffer = calloc(buffer_size, sizeof(LADSPA_Data));

plugin_data->buffer_pos_w=0;

plugin_data->buffer_pos_r=0;

]]></callback>

<callback event="activate"><![CDATA[

memset(buffer, 0, buffer_size * sizeof(LADSPA_Data));

]]></callback>

<callback event="connect_port"><![CDATA[

]]></callback>

<callback event="cleanup"><![CDATA[

free(plugin_data->buffer);

]]></callback>

<callback event="run"><![CDATA[

unsigned long pos;

unsigned int tmp;

LADSPA_Data * p;

tmp=(int)(del*fs/1000);

if(tmp!=buffer_offset)

{

plugin_data->buffer_pos_w=tmp>=plugin_data->buffer_size?plugin_data->buffer_size-1:tmp-1;

buffer_offset=tmp;

}

tmp=(int)(channel+0.1);

for (pos = 0; pos < sample_count; pos++) {

/*put the data into buf*/

p= tmp==1?in_l:in_r;

plugin_data->buffer[plugin_data->buffer_pos_w]=p[pos];

plugin_data->buffer_pos_w=plugin_data->buffer_pos_w>=plugin_data->buffer_size?0:plugin_data->buffer_pos_w+1;

/* Left and right channel outs */

if(p==in_l)

{

buffer_write(out_l[pos], plugin_data->buffer[plugin_data->buffer_pos_r]);

buffer_write(out_r[pos], in_r[pos] );

}

else{

buffer_write(out_l[pos], in_l[pos] );

buffer_write(out_r[pos], plugin_data->buffer[plugin_data->buffer_pos_r]);

}

plugin_data->buffer_pos_r=plugin_data->buffer_pos_r>=plugin_data->buffer_size?0:plugin_data->buffer_pos_r+1;

}

]]></callback>

<port label="del" dir="input" type="control" hint="default_low">

<name>delay (ms)</name>

<p>The delay of the left/right output in milliseconds.</p>

<range min="1" max="2700"/>

</port>

<port label="channel" dir="input" type="control" hint="default_low">

<name>channel to delay</name>

<p>The channel need to delay.</p>

<range min="1" max="2"/>

</port>

<port label="in_l" dir="input" type="audio">

<name>L input</name>

</port>

<port label="in_r" dir="input" type="audio">

<name>R input</name>

</port>

<port label="out_l" dir="output" type="audio">

<name>L output</name>

</port>

<port label="out_r" dir="output" type="audio">

<name>R output</name>

</port>

<instance-data label="buffer" type="LADSPA_Data *" />

<instance-data label="buffer_pos_w" type="unsigned int" />

<instance-data label="buffer_pos_r" type="unsigned int" />

<instance-data label="buffer_size" type="unsigned int" />

<instance-data label="fs" type="float" />

</plugin>