pcm_resample: choose the fallback resampler at runtime

Even if libsamplerate support is enabled, compile the fallback
resampler.  When the user specifies the option
"samplerate_converter=internal", it is chosen in favor of
libsamplerate.  This may help users with a weak FPU who don't want to
compile a custom MPD from source, because the fallback resampler does
not use floating point operations.

Makefile.am

@@ -198,6 +198,7 @@ src_mpd_SOURCES = \
 	src/pcm_channels.c \
 	src/pcm_format.c \
 	src/pcm_resample.c \
+	src/pcm_resample_fallback.c \
 	src/pcm_dither.c \
 	src/permission.c \
 	src/player_thread.c \
@@ -240,8 +241,6 @@ endif
 
 if HAVE_LIBSAMPLERATE
 src_mpd_SOURCES += src/pcm_resample_libsamplerate.c
-else
-src_mpd_SOURCES += src/pcm_resample_fallback.c
 endif
 
 if HAVE_ID3TAG

NEWS

@@ -53,6 +53,7 @@ ver 0.15 - (200?/??/??)
 * 32 bit audio support
 * Print available protocols in --version
 * fill buffer after seeking
+* choose the fallback resampler at runtime
 
 
 ver 0.14.2 (2009/02/13)

doc/mpd.conf.5

@@ -158,6 +158,11 @@ distortions.
 Linear Interpolator (4)
 
 Linear interpolator, very fast, poor quality.
+.TP
+internal
+
+Poor quality, no floating point operations.  This is the default (and
+only choice) if MPD was compiled without libsamplerate.
 .RE
 .IP
 For an up-to-date list of available converters, please see the libsamplerate

src/pcm_resample.c

@@ -20,15 +20,30 @@
 #include "pcm_resample_internal.h"
 #include "config.h"
 
+#ifdef HAVE_LIBSAMPLERATE
+#include "conf.h"
+#endif
+
 #include <string.h>
 
+#ifdef HAVE_LIBSAMPLERATE
+static bool
+pcm_resample_lsr_enabled(void)
+{
+	return strcmp(config_get_string(CONF_SAMPLERATE_CONVERTER, ""),
+		      "internal") == 0;
+}
+#endif
+
 void pcm_resample_init(struct pcm_resample_state *state)
 {
 	memset(state, 0, sizeof(*state));
 
 #ifdef HAVE_LIBSAMPLERATE
-	pcm_buffer_init(&state->in);
-	pcm_buffer_init(&state->out);
+	if (pcm_resample_lsr_enabled()) {
+		pcm_buffer_init(&state->in);
+		pcm_buffer_init(&state->out);
+	}
 #endif
 
 	pcm_buffer_init(&state->buffer);
@@ -37,10 +52,11 @@ void pcm_resample_init(struct pcm_resample_state *state)
 void pcm_resample_deinit(struct pcm_resample_state *state)
 {
 #ifdef HAVE_LIBSAMPLERATE
-	pcm_resample_lsr_deinit(state);
-#else
-	pcm_resample_fallback_deinit(state);
+	if (pcm_resample_lsr_enabled())
+		pcm_resample_lsr_deinit(state);
+	else
 #endif
+		pcm_resample_fallback_deinit(state);
 }
 
 const int16_t *
@@ -52,14 +68,15 @@ pcm_resample_16(struct pcm_resample_state *state,
 		size_t *dest_size_r)
 {
 #ifdef HAVE_LIBSAMPLERATE
-	return pcm_resample_lsr_16(state, channels,
-				   src_rate, src_buffer, src_size,
-				   dest_rate, dest_size_r);
-#else
+	if (pcm_resample_lsr_enabled())
+		return pcm_resample_lsr_16(state, channels,
+					   src_rate, src_buffer, src_size,
+					   dest_rate, dest_size_r);
+#endif
+
 	return pcm_resample_fallback_16(state, channels,
 					src_rate, src_buffer, src_size,
 					dest_rate, dest_size_r);
-#endif
 }
 
 const int32_t *
@@ -71,12 +88,13 @@ pcm_resample_32(struct pcm_resample_state *state,
 		size_t *dest_size_r)
 {
 #ifdef HAVE_LIBSAMPLERATE
-	return pcm_resample_lsr_32(state, channels,
-				   src_rate, src_buffer, src_size,
-				   dest_rate, dest_size_r);
-#else
+	if (pcm_resample_lsr_enabled())
+		return pcm_resample_lsr_32(state, channels,
+					   src_rate, src_buffer, src_size,
+					   dest_rate, dest_size_r);
+#endif
+
 	return pcm_resample_fallback_32(state, channels,
 					src_rate, src_buffer, src_size,
 					dest_rate, dest_size_r);
-#endif
 }

src/pcm_resample_internal.h

@@ -52,7 +52,7 @@ pcm_resample_lsr_32(struct pcm_resample_state *state,
 		    unsigned dest_rate,
 		    size_t *dest_size_r);
 
-#else
+#endif
 
 void
 pcm_resample_fallback_deinit(struct pcm_resample_state *state);
@@ -75,5 +75,3 @@ pcm_resample_fallback_32(struct pcm_resample_state *state,
 			 size_t *dest_size_r);
 
 #endif
-
-#endif