Fix AV1 and VP9 codec matching

Currently, AV1 or VP9 formats are matched regardless of the profile
parameter. This was not noticeable until browsers started advertising
multiple VP9 formats at the same time, each with a different profile
ID, in order to allow the counterpart to send different streams on the
basis of supported profiles.

This causes two issues: first, the library includes in the SDP all
formats passed by the browser, regardless of the fact that the profile
ID is registered in the API or not. Then, the library is unable to
choose the correct format for streaming, causing an intermittent
failure.

This patch fixes the matching algorithm and also covers the case in
which the profile ID is missing, by using values dictated by
specifications.

Tests were refactored since previous ones covered the same lines
multiple times.

internal/fmtp/av1.go

@@ -0,0 +1,40 @@
+// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
+// SPDX-License-Identifier: MIT
+
+package fmtp
+
+type av1FMTP struct {
+	parameters map[string]string
+}
+
+func (h *av1FMTP) MimeType() string {
+	return "video/av1"
+}
+
+func (h *av1FMTP) Match(b FMTP) bool {
+	c, ok := b.(*av1FMTP)
+	if !ok {
+		return false
+	}
+
+	// AV1 RTP specification:
+	// If the profile parameter is not present, it MUST be inferred to be 0 (“Main” profile).
+	hProfile, ok := h.parameters["profile"]
+	if !ok {
+		hProfile = "0"
+	}
+	cProfile, ok := c.parameters["profile"]
+	if !ok {
+		cProfile = "0"
+	}
+	if hProfile != cProfile {
+		return false
+	}
+
+	return true
+}
+
+func (h *av1FMTP) Parameter(key string) (string, bool) {
+	v, ok := h.parameters[key]
+	return v, ok
+}

internal/fmtp/fmtp.go

@@ -8,6 +8,22 @@ import (
 	"strings"
 )
 
+func parseParameters(line string) map[string]string {
+	parameters := make(map[string]string)
+
+	for _, p := range strings.Split(line, ";") {
+		pp := strings.SplitN(strings.TrimSpace(p), "=", 2)
+		key := strings.ToLower(pp[0])
+		var value string
+		if len(pp) > 1 {
+			value = pp[1]
+		}
+		parameters[key] = value
+	}
+
+	return parameters
+}
+
 // FMTP interface for implementing custom
 // FMTP parsers based on MimeType
 type FMTP interface {
@@ -23,29 +39,30 @@ type FMTP interface {
 }
 
 // Parse parses an fmtp string based on the MimeType
-func Parse(mimetype, line string) FMTP {
+func Parse(mimeType, line string) FMTP {
 	var f FMTP
 
-	parameters := make(map[string]string)
-
-	for _, p := range strings.Split(line, ";") {
-		pp := strings.SplitN(strings.TrimSpace(p), "=", 2)
-		key := strings.ToLower(pp[0])
-		var value string
-		if len(pp) > 1 {
-			value = pp[1]
-		}
-		parameters[key] = value
-	}
+	parameters := parseParameters(line)
 
 	switch {
-	case strings.EqualFold(mimetype, "video/h264"):
+	case strings.EqualFold(mimeType, "video/h264"):
 		f = &h264FMTP{
 			parameters: parameters,
 		}
+
+	case strings.EqualFold(mimeType, "video/vp9"):
+		f = &vp9FMTP{
+			parameters: parameters,
+		}
+
+	case strings.EqualFold(mimeType, "video/av1"):
+		f = &av1FMTP{
+			parameters: parameters,
+		}
+
 	default:
 		f = &genericFMTP{
-			mimeType:   mimetype,
+			mimeType:   mimeType,
 			parameters: parameters,
 		}
 	}