pcm/SoxrResampler: Add configurable quality levels

doc/user.xml

@@ -700,10 +700,47 @@ systemctl start mpd.socket</programlisting>
 
               <row>
                 <entry>
+                  "<parameter>soxr very high</parameter>"
+                </entry>
+                <entry>
+                  Use libsoxr with "Very High Quality" setting.
+                </entry>
+              </row>
+
+              <row>
+                <entry>
+                  "<parameter>soxr high</parameter>" or
                   "<parameter>soxr</parameter>"
                 </entry>
                 <entry>
-                  Use libsoxr.
+                  Use libsoxr with "High Quality" setting.
+                </entry>
+              </row>
+
+              <row>
+                <entry>
+                  "<parameter>soxr medium</parameter>"
+                </entry>
+                <entry>
+                  Use libsoxr with "Medium Quality" setting.
+                </entry>
+              </row>
+
+              <row>
+                <entry>
+                  "<parameter>soxr low</parameter>"
+                </entry>
+                <entry>
+                  Use libsoxr with "Low Quality" setting.
+                </entry>
+              </row>
+
+              <row>
+                <entry>
+                  "<parameter>soxr quick</parameter>"
+                </entry>
+                <entry>
+                  Use libsoxr with "Quick" setting.
                 </entry>
               </row>
 

src/pcm/ConfiguredResampler.cxx

@@ -59,9 +59,9 @@ pcm_resampler_global_init(Error &error)
 		return true;
 
 #ifdef HAVE_SOXR
-	if (strcmp(converter, "soxr") == 0) {
+	if (memcmp(converter, "soxr", 4) == 0) {
 		selected_resampler = SelectedResampler::SOXR;
-		return true;
+		return pcm_resample_soxr_global_init(converter, error);
 	}
 #endif
 

src/pcm/SoxrResampler.cxx

@@ -31,6 +31,72 @@
 
 static constexpr Domain soxr_domain("soxr");
 
+static unsigned long soxr_quality_recipe = SOXR_HQ;
+
+static const char *
+soxr_quality_name(unsigned long recipe)
+{
+	switch (recipe) {
+	case SOXR_VHQ:
+		return "Very High Quality";
+	case SOXR_HQ:
+		return "High Quality";
+	case SOXR_MQ:
+		return "Medium Quality";
+	case SOXR_LQ:
+		return "Low Quality";
+	case SOXR_QQ:
+		return "Quick";
+	}
+
+	gcc_unreachable();
+}
+
+static bool
+soxr_parse_converter(const char *converter)
+{
+	assert(converter != nullptr);
+
+	assert(memcmp(converter, "soxr", 4) == 0);
+	if (converter[4] == '\0')
+		return true;
+	if (converter[4] != ' ')
+		return false;
+
+	// converter example is "soxr very high", we want the "very high" part
+	const char *quality = converter + 5;
+	if (strcmp(quality, "very high") == 0)
+		soxr_quality_recipe = SOXR_VHQ;
+	else if (strcmp(quality, "high") == 0)
+		soxr_quality_recipe = SOXR_HQ;
+	else if (strcmp(quality, "medium") == 0)
+		soxr_quality_recipe = SOXR_MQ;
+	else if (strcmp(quality, "low") == 0)
+		soxr_quality_recipe = SOXR_LQ;
+	else if (strcmp(quality, "quick") == 0)
+		soxr_quality_recipe = SOXR_QQ;
+	else
+		return false;
+
+	return true;
+}
+
+bool
+pcm_resample_soxr_global_init(const char *converter, Error &error)
+{
+	if (!soxr_parse_converter(converter)) {
+		error.Format(soxr_domain,
+			    "unknown samplerate converter '%s'", converter);
+		return false;
+	}
+
+	FormatDebug(soxr_domain,
+		    "soxr converter '%s'",
+		    soxr_quality_name(soxr_quality_recipe));
+
+	return true;
+}
+
 AudioFormat
 SoxrPcmResampler::Open(AudioFormat &af, unsigned new_sample_rate,
 		       Error &error)
@@ -39,9 +105,10 @@ SoxrPcmResampler::Open(AudioFormat &af, unsigned new_sample_rate,
 	assert(audio_valid_sample_rate(new_sample_rate));
 
 	soxr_error_t e;
+	soxr_quality_spec_t quality = soxr_quality_spec(soxr_quality_recipe, 0);
 	soxr = soxr_create(af.sample_rate, new_sample_rate,
 			   af.channels, &e,
-			   nullptr, nullptr, nullptr);
+			   nullptr, &quality, nullptr);
 	if (soxr == nullptr) {
 		error.Format(soxr_domain,
 			     "soxr initialization has failed: %s", e);

src/pcm/SoxrResampler.hxx

@@ -44,4 +44,7 @@ public:
 					   Error &error) override;
 };
 
+bool
+pcm_resample_soxr_global_init(const char *converter, Error &error);
+
 #endif