Offer API to precalculate final WAV size (including header)

[MathieuDuponchelle]

Hey, I have a use case where I need to send a WAV file to a service that doesn't accept samples larger than 11 MB. I would love some API to anticipate that before adding more samples to my current writer :)

[ruuda]

There is WavWriter::len which returns the number of samples written so far. You can multiply that by the number of bytes per sample of your chosen format.

[MathieuDuponchelle]

@ruuda thanks for the prompt answer, however this will not include the expected size of the WAV header that will be added on finalization right?

[ruuda]

No, it doesn’t. If you want to know the size of the file itself, you could query that from the underlying writer (which I suppose is inconvenient, because Hound takes ownership of it; maybe a method WavWriter::inner(&self) -> &W would help?). The size of the header is constant for a given sample format, so you could measure its size once and then subtract it.

Also, the header is written at the start, finalization does not change the file size. After all samples are written, Hound needs to seek back to update fields in the header, but that does not affect the final file size.

[MathieuDuponchelle]

Also, the header is written at the start, finalization does not change the file size. After all samples are written, Hound needs to seek back to update fields in the header, but that does not affect the final file size.

Ah that is the piece of info I needed, thanks. re inner method, something to retrieve a reference would be nice yes.

It would also be nice to simply get back the ownership on finalize(), that would let me avoid the pattern I mentioned there: #85 (comment) . I don't know if it would be right semantically to have an into_inner() method that also finalizes however.

[ruuda]

It would also be nice to simply get back the ownership on finalize()

Yes, I agree. Until then, you can pass in an &mut io::Write rather than an io::Write, and then the borrow ends when the WavWriter is destroyed, making the original writer available again. It’s slightly less general, but maybe it solves your problem already?

[MathieuDuponchelle]

It’s slightly less general, but maybe it solves your problem already?

It might, I'll need to test :)