pcm/SoxrResampler: round output buffer size up

The old formula calculates the output buffer size with "regular" rounding (to the nearest integer), however sometimes, that is insufficient and the last sample cannot be resampled. This causes audible distortions. By changing the formula to consider the worst case (always round up), this problem is eliminated.

pcm/SoxrResampler: round output buffer size up
8d036c4b · Max Kellermann · 8ff0d990 · 8d036c4b · 8d036c4b
Commit 8d036c4b authored Nov 10, 2014 by Max Kellermann
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NEWS NEWS +1 -0

SoxrResampler.cxx src/pcm/SoxrResampler.cxx +2 -1

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--- a/NEWS
+++ b/NEWS
@@ -9,6 +9,7 @@ ver 0.19.3 (not yet released)
  - audiofile: fix crash while playing streams
  - audiofile: fix bit rate calculation
  - ffmpeg: support opus
+* fix distorted audio with soxr resampler

 ver 0.19.2 (2014/11/02)
 * input

--- a/src/pcm/SoxrResampler.cxx
+++ b/src/pcm/SoxrResampler.cxx
@@ -147,7 +147,8 @@ SoxrPcmResampler::Resample(ConstBuffer<void> src, Error &error)

 	const size_t n_frames = src.size / frame_size;

-	const size_t o_frames = size_t(n_frames * ratio + 0.5);
+	/* always round up: worst case output buffer size */
+	const size_t o_frames = size_t(n_frames * ratio) + 1;

 	float *output_buffer = (float *)buffer.Get(o_frames * frame_size);