flac: fix off-by-one in sample conversion

[mewmew]

Issue spotted by @mehrvarz.

[mewmew]

@faiface Do you think this issue is also present in the WAV decoder?

The fix is based on https://github.com/zikichombo/sound/blob/master/sample/fix.go#L25

func ToFloat(d int64, nBits int) float64 {
	s := float64(int64(1 << uint(nBits-1)))
	return float64(d) / s
}

[faiface]

Thanks for the fix!

[mewmew]

re: @faiface Thanks for merging. When you get a chance, would you mind checking if this is present in the WAV decoder?

Edit: since I copied the logic of the flac decoder from the WAV decoder.

@faiface Do you think this issue is also present in the WAV decoder?

[faiface]

I'm not really sure, I'm looking at the code right now, but it seems to me it should be correct (https://github.com/faiface/beep/blob/master/wav/decode.go#L220), but I'm not really sure, and don't have the time to properly test it right now.

[faiface]

Btw, is there any way I can contact you more directly?

[mewmew]

Btw, is there any way I can contact you more directly?

Sent you contact info per e-mail. I'll be off for the evening, but send a PM if you get it to work; so at least we know the communication channel is working.

Wish you a good evening :)
Cheers /u