How to reverse an audio file?

Question

I\'d like to reverse an existing audio file (e.g. WAV, CAF, ...) on iOS. Any suggestions on how to achieve this? Open-source libraries?

Answer 1

Using libsndfile, I was able to read in the recorded audio sample. The following code snippet then shows how to open the input file, and write the output in reversed order. You should note though that all data is read in memory!

SF_INFO info_read;
info_read.format = 0;
SNDFILE* sndfilein = sf_open("my_input_file.caf", SFM_READ, &info_read);

SF_INFO info_write;
info_write.format = info.format;
info_write.channels = info.channels;
info_write.frames = info.frames;
info_write.samplerate = info.samplerate;
info_write.sections = info.sections;
info_write.seekable = info.seekable;

SNDFILE* sndfileout = sf_open("my_output_file.caf", SFM_RDWR, &info_write);

int* buf = new int[8000 * 30];
int framesRead = sf_readf_int(sndfilein, buf, info.frames);
for (int i = 0; i < info.frames; i++)
    sf_writef_int(sndfileout, &buf[info.frames - i], 1);
delete[] buf;

sf_close(sndfilein);
sf_close(sndfileout);