PcmResampleLibsamplerate: clip 24 bit data

Using pcm_resample_lsr_32() for 24 bit samples works, but may cause 24
bit overflows.  This commit makes 24 bit a special case with explicit
clipping.

NEWS

@@ -7,6 +7,7 @@ ver 0.18.5 (20??/??/??)
   - proxy: provide "db_update" in "stats" response
 * decoder
   - fluidsynth: auto-detect by default
+* clip 24 bit data from libsamplerate
 * fix ia64, mipsel and other little-endian architectures
 * fix build failures due to missing includes
 * fix build failure with static libmpdclient

src/pcm/PcmResample.cxx

@@ -155,8 +155,19 @@ PcmResampler::Resample24(unsigned channels, unsigned src_rate,
 			 unsigned dest_rate, size_t *dest_size_r,
 			 Error &error_r)
 {
+#ifdef HAVE_LIBSAMPLERATE
+	if (pcm_resample_lsr_enabled())
+		return pcm_resample_lsr_24(this, channels,
+					   src_rate, src_buffer, src_size,
+					   dest_rate, dest_size_r,
+					   error_r);
+#else
+	(void)error_r;
+#endif
+
 	/* reuse the 32 bit code - the resampler code doesn't care if
 	   the upper 8 bits are actually used */
-	return Resample32(channels, src_rate, src_buffer, src_size,
-			  dest_rate, dest_size_r, error_r);
+	return pcm_resample_fallback_32(this, channels,
+					src_rate, src_buffer, src_size,
+					dest_rate, dest_size_r);
 }

src/pcm/PcmResampleInternal.hxx

@@ -69,6 +69,15 @@ pcm_resample_lsr_32(PcmResampler *state,
 		    unsigned dest_rate, size_t *dest_size_r,
 		    Error &error);
 
+const int32_t *
+pcm_resample_lsr_24(PcmResampler *state,
+		    unsigned channels,
+		    unsigned src_rate,
+		    const int32_t *src_buffer,
+		    size_t src_size,
+		    unsigned dest_rate, size_t *dest_size_r,
+		    Error &error);
+
 #endif
 
 const int16_t *

src/pcm/PcmResampleLibsamplerate.cxx

@@ -19,6 +19,7 @@
 
 #include "config.h"
 #include "PcmResampleInternal.hxx"
+#include "PcmUtils.hxx"
 #include "util/ASCII.hxx"
 #include "util/Error.hxx"
 #include "util/Domain.hxx"
@@ -283,3 +284,27 @@ pcm_resample_lsr_32(PcmResampler *state,
 
 	return dest_buffer;
 }
+
+const int32_t *
+pcm_resample_lsr_24(PcmResampler *state,
+		    unsigned channels,
+		    unsigned src_rate,
+		    const int32_t *src_buffer, size_t src_size,
+		    unsigned dest_rate, size_t *dest_size_r,
+		    Error &error)
+{
+	const auto result = pcm_resample_lsr_32(state, channels,
+						src_rate, src_buffer, src_size,
+						dest_rate, dest_size_r,
+						error);
+	if (result != nullptr)
+		/* src_float_to_int_array() clamps for 32 bit
+		   integers; now make sure everything's fine for 24
+		   bit */
+		/* TODO: eliminate the 32 bit clamp to reduce overhead */
+		PcmClampN<int32_t, int32_t, 24>(const_cast<int32_t *>(result),
+						result,
+						*dest_size_r / sizeof(*result));
+
+	return result;
+}