alsa plugin data flow for capture

Hi All
Could any one tell me how does the data flow like for arecord with alsa plugin?
I found the description on alsa document, with a plugin definition in asound.conf


pcm.myplugdev {
    type plug
    slave { 
        pcm default 
        rate 48000
    }
}

the data flow for aplay ：aplay -D myplugdev foobar.wav as follows
aplay--> myplugdev (plugin named "plug" converts rate) --> default --> hw:0,0



How about the data flow for arecord：aplay -D myplugdev -c 2 -r 48000 save.wav
should be like this? No matter what sample rate for input source , the save.wav should always be 48000? 
arecord--> hw:0,0->default->myplugdev (plugin named "plug" converts rate) --> save.wav?


It is wired it does not work when I am using a dummy codec to capture  I2S audio data to a file, the sample rate is always the same with the source, it seems the converts rate plugin does not work.
Who can kindly give me an explanation for it? I am new to alsa.


Thanks

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