Hi android devs!
How can I record a double[] or byte[] into a pcm in order to convert it to a wav file?
My life depends on this one 😬

You just spit out a WAV file header and then the data: http://soundfile.sapp.org/doc/...

C header definition: https://gist.github.com/Jon-Schneid...

@Fast-Nop how can i apply since it is a c++ lib?

@R1100 You'd build up that structure in memory and then write it to disk via file I/O. Here a C function for writing the header of a 16 bit mono WAV, that's how I did it 20 years ago (error handling omitted):

(The crazy shifting stuff is to make sure it works regardless of endianess.)

@R1100

void write_wave_header(FILE *wav_file, long wav_cnt, unsigned long s_freq)

{

unsigned long totalsize,bytespersec;

fprintf(wav_file,"RIFF");

totalsize = 2 * wav_cnt + 36;

fputc((totalsize & 0x000000ff),wav_file); /* File size */

fputc((totalsize & 0x0000ff00) >> 8,wav_file);

fputc((totalsize & 0x00ff0000) >> 16,wav_file);

fputc((totalsize & 0xff000000) >> 24,wav_file);

fprintf(wav_file,"WAVE");

fprintf(wav_file,"fmt "); /* fmt_ chunk */

fputc(16,wav_file); /* Chunk size */

fputc(0,wav_file);

fputc(0,wav_file);

fputc(0,wav_file);

fputc(1,wav_file); /* Format tag - uncompressed */

fputc(0,wav_file);

fputc(1,wav_file); /* Channels */

fputc(0,wav_file);

@R1100

fputc((s_freq & 0x000000ff),wav_file); /* Sample frequency (Hz) */

fputc((s_freq & 0x0000ff00) >> 8,wav_file);

fputc((s_freq & 0x00ff0000) >> 16,wav_file);

fputc((s_freq & 0xff000000) >> 24,wav_file);

bytespersec = 2 * s_freq;

fputc((bytespersec & 0x000000ff),wav_file); /* Average bytes per second */

fputc((bytespersec & 0x0000ff00) >> 8,wav_file);

fputc((bytespersec & 0x00ff0000) >> 16,wav_file);

fputc((bytespersec & 0xff000000) >> 24,wav_file);

fputc(2,wav_file); /* Block alignment */

fputc(0,wav_file);

fputc(16,wav_file); /* Bits per sample */

fputc(0,wav_file);

fprintf(wav_file,"data");

totalsize = 2 * wav_cnt;

fputc((totalsize & 0x000000ff),wav_file); /* Data size */

fputc((totalsize & 0x0000ff00) >> 8,wav_file);

fputc((totalsize & 0x00ff0000) >> 16,wav_file);

fputc((totalsize & 0xff000000) >> 24,wav_file);

}

@Fast-Nop thanks bro !
U saved me 😀

@Fast-Nop can i convert it to java to be able to use it as a class?

@R1100 Java should already have that since Java has classes for everything. Is that one here available?

http://labbookpages.co.uk/audio/...

https://pamguard.org/devDocs/...

@Fast-Nop yesss!
There is a lib named wavfiles
Hope it works

Do my homework 😭

@Fast-Nop Shouldn’t that gist contain an aligned attribute or maybe switch to uint32 instead of char[4] to ensure the correct alignment is used? That first char array might not be guaranteed to be placed on a 32-bit aligned address and if not might result in extra pad bytes to be inserted which would likely result in a malformed header.

@aether the overall alignment of a struct is always the alignment of the biggest elementary data type that it contains. If a struct contains a 4 byte integer, the struct will always start at an address that is divisible by 4 even if that integer is not the first element.

The issue why the Github gist is a little sloppy is that it assumes int to be 4 bytes, but the C standard guarantees only 2 bytes. That should have been done with the C99 data types. However, on PCs and Android, int is 4 bytes so that it will work.

@Fast-Nop ah right you are. I mixed up the rule in my head.