CODEWITHSUNDEEP
compressionmp3wavrun-length-encoding
rossmcm
rossmcm

Reputation: 5640

Can the mp3 or wav file format take advantage of repetitious sounds?

I want to store a number of sound fragments as MP3 or WAV files, but these fragments are each highly repetitive (a 10 second burst of tone for example). Are the MP3 or WAV file formats able to take advantage of this - i.e. is there a sound file equivalent of run-length encoding?

Upvotes: 1

Views: 301

Answers (1)

Brad
Brad

Reputation: 163488

No, neither codec can do this.

WAV files (typically) use PCM, which holds a value for every single sample. Even if there were complete digital silence (all values the same), every sample is stored.

MP3 works in frames of 1,152 samples. Each frame stands alone (well, there is the bit reservoir but for the purpose of encoding/decoding, this is just extra bandwidth made available). Even if there were a way to say do-this-n-times, it would be fixed within a frame. Now, if you are using MP3 with variable bit rate, I suspect that you will have great results with perfect sine waves since they have no harmonics. MP3 works by converting from the time domain to the frequency domain. That is, it samples the frequencies in each frame. If you only have one of those frequencies (or no sound at all), the VBR method would be efficient.

I should note that FLAC does use RLE when encoding silence. However, I don't think FLAC could be hacked to use RLE for 10 seconds of audio, since again there is a frame border. FLAC's RLE for silence is problematic for live internet radio stations that leave a few second gap inbetween songs. It's important for these stations to have a large buffer, since clients will often pause the stream if they don't receive enough data. (They do get caught back up again though as soon as that silent block is sent, once audio resumes.)

Upvotes: 2

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