Hello,

I'm looking for a faster way to de-interleave binary data. I have some source files (~200MB in size) of interleaved data that contain two data streams. The data is interleaved one bit at a time (e.g., if stream one is all 1's and stream two is all 0's, the file would read as "1010101010101010....", and I would like the resultant files to read "1111111..." and "000000...").

The code below works, but is slow (so it seems to me - it takes about 40 minutes to de-interleave a 192MB file on a modern laptop). I read in some data, split each bit into an array, the split that array into two sub arrays, then write it back out. I'm a newbie to Perl and programming in general, which may be obvious from my code. 

until ($filesize <= $offset)
{
        sysseek (INTERLEAVED_DATA, $offset, 0);
        sysread (INTERLEAVED_DATA, $buffer, 8192);

        @interleaved = split(//, unpack("b*", $buffer));
        $buffer = "";
    
        while (@interleaved){

        push @uninterleaved_1, shift @interleaved;
        push @uninterleaved_2, shift @interleaved;
        }

        $uninterleaved_1 = pack "b*", join "", @uninterleaved_1;
        @uninterleaved_1 = "";

        $uninterleaved_2 = pack "b*", join "", @uninterleaved_2;
        @uninterleaved_2 = "";
     
        syswrite (UNINTERLEAVED_1, $uninterleaved_1);
        syswrite (UNINTERLEAVED_2, $uninterleaved_2);

        $uninterleaved_1 = "";
    $uninterleaved_2 = "";
        
        $offset = $offset + 8192;
}

[download]
I've tried reading in bigger chunks of data, but it doesn't help. It seems it's all the unpacking and array operations that take the most time. Thanks.

In reply to de-interleaving binary data by joe_b

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