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From: Alex Shulgin on 8 Jan 2008 22:49
On Jan 8, 4:20 pm, sidkdbl07 <sidkwak...(a)gmail.com> wrote:
>
> On Dec 15 2007, 3:56 pm, Alex Shulgin <alex.shul...(a)gmail.com> wrote:
>
> > On Dec 15, 6:12 am, sidkdbl07 <sidkwak...(a)gmail.com> wrote:
>
> > > I have a binary file with 16-bit samples and I'd like to down convert
> > > to 1-bit
>
> > > Here's what I have but it doesn't work. any suggestions?
>
> > You cannot feed a binary file to your program and expect it to work.
> > Try this instead:
>
> > $ cat input.txt
> > 0000000000000000
> > 1111111111111111
> > $ ./a.out input.txt
> > Found on
> > $ cat output.bin
> > 01
>
> I don't understand why I can't load a binary file and expect it to
> work. I have a binary file that was written with 16-bit samples. Ergo,
> if I read in 16 bits, then I should have one sample, no?
>
> Your file called input.txt is an ASCII file, so it doesn't look like
> it would really serve my purposes. Please correct me if I'm wrong.

Sorry, I think I wasn't specific enough but hoped that you could
figure out the rest by yourself. :)

My point was that you cannot feed a binary file to _the_ program you
posted, not that you can't do that with some other program. The
problem here is that std::bitset<n> once read from the stream expects
a series of characters representing 'zero' and 'one', not n-bit
samples. So one of the ways to solve you problem is to read samples
by hand, like this:

std::ifstream input(infile, std::ios::binary);
std::ofstream output(outfile, std::ios::binary);
uint8_t out = 0;
size_t bits = 0;
while (input)
{
uint16_t sample;
input.read(& sample, sizeof(sample));
if (input.eof()) break;

// TODO: handle byte-order

if (sample & 0x8000) // highest bit set
// add up the sample to 'out'
++bits;

if (bits == sizeof(out))
{
output.write(& out, sizeof(out));
bits = 0;
}
}

You have to decide on byte-order of the input samples and bit-order of
the output samples in order for this to work across platforms.


Good luck!
--
Alex Shulgin
PS: the code is out of the top of my head -- might not even compile.

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