The format is fairly complicated, but I need to take 4 bytes from that
buffer and extract two 12-bit numbers from that 32-bit string (along with
some reversing operations, as you can see in the function). I cannot seem
to find bit operations that address/concatenate individual bits without
going through a string format and parsing. Would you have any guidance as
to where in the manual I should look?
On Thursday, October 6, 2016 at 8:15:41 PM UTC-4, Yichao Yu wrote:
>
> On Thu, Oct 6, 2016 at 5:40 PM, Jérémy Béjanin <jeremy....@gmail.com
> <javascript:>> wrote:
> > Thanks! this works perfectly.
> >
> > The pointer_to_array() function seems to be deprecated, however, do you
> know
> > how to use the suggested replacement, unsafe_wrap()?
>
> Yes.
>
> >
> > And if it's not too much to ask, I am wondering how I can do the
> conversion
> > from this UInt8 buffer more efficiently. This is what I am currently
> doing,
> > where blocks is the buffer:
> >
> > # We now have all the blocks in the blocks array, we need to extract the
> > # 12-bit samples from that array. The data in the blocks is organized in
> 4
> > # bytes / 32-bit words, and each word contains two 12-bit samples.
> > # Calculate the number of 32-bit words in the blocks array
> > numwords = div(numblocks*DIG_BLOCK_SIZE,4)
> > # Initialize array to store the samples
> > data = Array{Int32}(2*numwords)
> > for n=1:numwords
> > # Convert next four bytes to 32-bit string
> > s =
> >
> reverse(bits(blocks[(n-1)*4+1]))*reverse(bits(blocks[(n-1)*4+2]))*reverse(bits(blocks[(n-1)*4+3]))*reverse(bits(blocks[(n-1)*4+4]))
>
>
> > # Parse the first 12 bits as the first sample and the 12 bits 4 bits
> > later as the second sample
> > data[(n-1)*2+1] = parse(Int,reverse(s[1:12]),2)
> > data[(n-1)*2+2] = parse(Int,reverse(s[17:28]),2)
> > end
> >
> > This is pretty slow, I assume due to the translation between numbers and
> > strings. Is there a better way to do this?
>
> I don't know what exactly the format is but you should not go though
> string and you should be able to do what you want with simple
> interger/bits operations.
>
> >
> > Thanks,
> > Jeremy
> >
>
