Improved track format selection

player/format.go

@@ -16,3 +16,27 @@ func formatBitrate(format metadatapb.AudioFile_Format) int {
 		return 0
 	}
 }
+
+func selectBestFormat(files []*metadatapb.AudioFile, preferredBitrate int) *metadatapb.AudioFile {
+	absDist := func(a, b int) int {
+		if a > b {
+			return a - b
+		} else {
+			return b - a
+		}
+	}
+
+	// pick the best format by selecting which has the smallest distance from the preferred bitrate
+	var best *metadatapb.AudioFile
+	var bestDist int
+	for _, ff := range files {
+		bitrate := formatBitrate(*ff.Format)
+		dist := absDist(bitrate, preferredBitrate)
+		if best == nil || dist < bestDist {
+			best = ff
+			bestDist = dist
+		}
+	}
+
+	return best
+}

player/player.go

@@ -222,16 +222,9 @@ func (p *Player) NewStream(tid librespot.TrackId, bitrate int, trackPosition int
 		}
 	}
 
-	var file *metadatapb.AudioFile
-	for _, ff := range trackMeta.File {
-		if formatBitrate(*ff.Format) == bitrate {
-			file = ff
-			break
-		}
-	}
-
+	file := selectBestFormat(trackMeta.File, bitrate)
 	if file == nil {
-		return nil, fmt.Errorf("failed fetching requested bitrate: %d", bitrate)
+		return nil, fmt.Errorf("no playable formats for %s", tid.Uri())
 	}
 
 	log.Debugf("selected format %s for %s", file.Format.String(), tid.Uri())