CODEWITHSUNDEEP
c++audiowav
user3621123
user3621123

Reputation:

computing duration of a wav file

I am trying to edit a wav file using c++ by directly reading its binary data. I have written the file's header as follows: 

struct header{    
char chunk_id[4];
int chunk_size;
char format[4];
char subchunk1_id[4];
int subchunk1_size;
short int audio_format;
short int num_channels;
int sample_rate;            
int byte_rate;
short int block_align;
short int bits_per_sample;
char subchunk2_id[4];
int subchunk2_size;
 };

Now how to compute the maximum duration of the sound track assuming that the header's data is already loaded in some variable?

Upvotes: 1

Views: 3059

Answers (1)

simonc
simonc

Reputation: 42165

Assuming a duration in seconds (rounded down) is good enough, you can simply use

int durationInSeconds(struct header* hdr)
{
    int numSamples = hdr->subchunk2_size /
                         (hdr->num_channels * (hdr->bits_per_sample/8));
    int durationSeconds = numSamples / hdr->sample_rate;
    return durationSeconds;
}

subchunk2_size gives you the number of bytes of audio data. Dividing this by the product of the number of samples and byte rate (note: bits_per_sample gives you the number of bits in a single sample for a single channel - this is different from byte_rate in header) gives you a total number of samples.

sample_rate is the number of samples per second so dividing the total number of samples by this gives you the total duration in seconds.

Upvotes: 6

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