diff --git a/internal/codecprocessor/h264_test.go b/internal/codecprocessor/h264_test.go
index 6f124fb6..fb20b5d5 100644
--- a/internal/codecprocessor/h264_test.go
+++ b/internal/codecprocessor/h264_test.go
@@ -208,7 +208,7 @@ func TestH264RTPOversized(t *testing.T) {
 		}))
 	require.NoError(t, err)
 
-	var out []*rtp.Packet
+	var out []*rtp.Packet //nolint:prealloc
 
 	for _, pkt := range []*rtp.Packet{
 		{
diff --git a/internal/codecprocessor/h265_test.go b/internal/codecprocessor/h265_test.go
index 67767ace..7b094d74 100644
--- a/internal/codecprocessor/h265_test.go
+++ b/internal/codecprocessor/h265_test.go
@@ -208,7 +208,7 @@ func TestH265RTPOversized(t *testing.T) {
 		}))
 	require.NoError(t, err)
 
-	var out []*rtp.Packet
+	var out []*rtp.Packet //nolint:prealloc
 
 	for _, pkt := range []*rtp.Packet{
 		{
diff --git a/internal/core/path.go b/internal/core/path.go
index a06973a8..955dc9fd 100644
--- a/internal/core/path.go
+++ b/internal/core/path.go
@@ -584,9 +584,11 @@ func (pa *path) doAPIPathsGet(req pathAPIPathsGetReq) {
 				return pa.stream.BytesSent()
 			}(),
 			Readers: func() []defs.APIPathSourceOrReader {
-				ret := []defs.APIPathSourceOrReader{}
+				ret := make([]defs.APIPathSourceOrReader, len(pa.readers))
+				i := 0
 				for r := range pa.readers {
-					ret = append(ret, r.APIReaderDescribe())
+					ret[i] = r.APIReaderDescribe()
+					i++
 				}
 				return ret
 			}(),
diff --git a/internal/defs/source.go b/internal/defs/source.go
index ae5fd893..0a0d39e4 100644
--- a/internal/defs/source.go
+++ b/internal/defs/source.go
@@ -42,22 +42,32 @@ func FormatsInfo(formats []format.Format) string {
 		strings.Join(FormatsToCodecs(formats), ", "))
 }
 
-// MediasToCodecs returns the name of codecs of given formats.
-func MediasToCodecs(medias []*description.Media) []string {
-	var formats []format.Format
+func gatherFormats(medias []*description.Media) []format.Format {
+	n := 0
 	for _, media := range medias {
-		formats = append(formats, media.Formats...)
+		n += len(media.Formats)
 	}
 
-	return FormatsToCodecs(formats)
+	if n == 0 {
+		return nil
+	}
+
+	formats := make([]format.Format, n)
+	n = 0
+
+	for _, media := range medias {
+		n += copy(formats[n:], media.Formats)
+	}
+
+	return formats
+}
+
+// MediasToCodecs returns the name of codecs of given formats.
+func MediasToCodecs(medias []*description.Media) []string {
+	return FormatsToCodecs(gatherFormats(medias))
 }
 
 // MediasInfo returns a description of medias.
 func MediasInfo(medias []*description.Media) string {
-	var formats []format.Format
-	for _, media := range medias {
-		formats = append(formats, media.Formats...)
-	}
-
-	return FormatsInfo(formats)
+	return FormatsInfo(gatherFormats(medias))
 }
diff --git a/internal/playback/on_get_test.go b/internal/playback/on_get_test.go
index c0139e90..540d1e6d 100644
--- a/internal/playback/on_get_test.go
+++ b/internal/playback/on_get_test.go
@@ -613,11 +613,11 @@ func TestOnGet(t *testing.T) {
 
 					sampleData := make(map[int][][]byte)
 					for _, track := range p.Tracks {
-						var samples [][]byte
-						for _, sample := range track.Samples {
+						samples := make([][]byte, len(track.Samples))
+						for i, sample := range track.Samples {
 							buf, err = sample.GetPayload()
 							require.NoError(t, err)
-							samples = append(samples, buf)
+							samples[i] = buf
 							sample.GetPayload = nil
 						}
 						sampleData[track.ID] = samples
diff --git a/internal/stream/reader.go b/internal/stream/reader.go
index 359d1426..e1767072 100644
--- a/internal/stream/reader.go
+++ b/internal/stream/reader.go
@@ -41,11 +41,24 @@ func (r *Reader) OnData(medi *description.Media, forma format.Format, cb OnDataF
 
 // Formats returns all formats for which the reader has registered a OnData callback.
 func (r *Reader) Formats() []format.Format {
-	var out []format.Format
+	n := 0
+	for _, formats := range r.onDatas {
+		for range formats {
+			n++
+		}
+	}
+
+	if n == 0 {
+		return nil
+	}
+
+	out := make([]format.Format, n)
+	n = 0
 
 	for _, formats := range r.onDatas {
 		for forma := range formats {
-			out = append(out, forma)
+			out[n] = forma
+			n++
 		}
 	}