audio_format: hack for DSD to USB conversion

src/audio_format.c

@@ -35,6 +35,15 @@ audio_format_mask_apply(struct audio_format *af,
 	assert(audio_format_valid(af));
 	assert(audio_format_mask_valid(mask));
 
+	if (af->format == SAMPLE_FORMAT_DSD &&
+	    mask->format == SAMPLE_FORMAT_DSD_OVER_USB &&
+	    mask->sample_rate == 0)
+		/* each DSD-over-USB sample contains 2 DSD bytes (16
+		   DSD bits), which means the sample rate must be
+		   halved; this is not the real 1 bit sample rate, but
+		   MPD's point of view */
+		af->sample_rate /= 2;
+
 	if (mask->sample_rate != 0)
 		af->sample_rate = mask->sample_rate;