diff --git a/call/rtcp_demuxer.cc b/call/rtcp_demuxer.cc
index e181d3a..d35548d 100644
--- a/call/rtcp_demuxer.cc
+++ b/call/rtcp_demuxer.cc
@@ -18,6 +18,7 @@
 #include "api/rtp_headers.h"
 #include "call/rtcp_packet_sink_interface.h"
 #include "call/rtp_rtcp_demuxer_helper.h"
+#include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
 #include "rtc_base/checks.h"
 
 namespace webrtc {
@@ -39,7 +40,7 @@
 
 void RtcpDemuxer::AddSink(const std::string& rsid,
                           RtcpPacketSinkInterface* sink) {
-  RTC_DCHECK(StreamId::IsLegalRsidName(rsid));
+  RTC_DCHECK(IsLegalRsidName(rsid));
   RTC_DCHECK(sink);
   RTC_DCHECK(!ContainerHasKey(broadcast_sinks_, sink));
   RTC_DCHECK(!MultimapAssociationExists(rsid_sinks_, rsid, sink));
diff --git a/call/rtp_demuxer.cc b/call/rtp_demuxer.cc
index 8f0e2e5..23f605d 100644
--- a/call/rtp_demuxer.cc
+++ b/call/rtp_demuxer.cc
@@ -38,8 +38,8 @@
                          RtpPacketSinkInterface* sink) {
   RTC_DCHECK(!criteria.payload_types.empty() || !criteria.ssrcs.empty() ||
              !criteria.mid.empty() || !criteria.rsid.empty());
-  RTC_DCHECK(criteria.mid.empty() || Mid::IsLegalMidName(criteria.mid));
-  RTC_DCHECK(criteria.rsid.empty() || StreamId::IsLegalRsidName(criteria.rsid));
+  RTC_DCHECK(criteria.mid.empty() || IsLegalMidName(criteria.mid));
+  RTC_DCHECK(criteria.rsid.empty() || IsLegalRsidName(criteria.rsid));
   RTC_DCHECK(sink);
 
   // We return false instead of DCHECKing for logical conflicts with the new
diff --git a/modules/rtp_rtcp/BUILD.gn b/modules/rtp_rtcp/BUILD.gn
index 9fe7fdc..2cabd1e 100644
--- a/modules/rtp_rtcp/BUILD.gn
+++ b/modules/rtp_rtcp/BUILD.gn
@@ -104,6 +104,7 @@
     "../../rtc_base/system:unused",
     "../../system_wrappers",
     "../video_coding:codec_globals_headers",
+    "//third_party/abseil-cpp/absl/strings",
     "//third_party/abseil-cpp/absl/types:optional",
     "//third_party/abseil-cpp/absl/types:variant",
   ]
diff --git a/modules/rtp_rtcp/include/rtp_rtcp_defines.cc b/modules/rtp_rtcp/include/rtp_rtcp_defines.cc
index d23d82d..20bd1e7 100644
--- a/modules/rtp_rtcp/include/rtp_rtcp_defines.cc
+++ b/modules/rtp_rtcp/include/rtp_rtcp_defines.cc
@@ -20,9 +20,8 @@
 
 namespace webrtc {
 
-StreamDataCounters::StreamDataCounters() : first_packet_time_ms(-1) {}
-
-constexpr size_t StreamId::kMaxSize;
+namespace {
+constexpr size_t kMidRsidMaxSize = 16;
 
 // Check if passed character is a "token-char" from RFC 4566.
 static bool IsTokenChar(char ch) {
@@ -31,16 +30,30 @@
          (ch >= 0x41 && ch <= 0x5a) || (ch >= 0x5e && ch <= 0x7e);
 }
 
-bool StreamId::IsLegalMidName(rtc::ArrayView<const char> name) {
-  return (name.size() <= kMaxSize && name.size() > 0 &&
+}  // namespace
+
+StreamDataCounters::StreamDataCounters() : first_packet_time_ms(-1) {}
+
+constexpr size_t StreamId::kMaxSize;
+
+bool IsLegalMidName(absl::string_view name) {
+  return (name.size() <= kMidRsidMaxSize && name.size() > 0 &&
           std::all_of(name.data(), name.data() + name.size(), IsTokenChar));
 }
 
-bool StreamId::IsLegalRsidName(rtc::ArrayView<const char> name) {
-  return (name.size() <= kMaxSize && name.size() > 0 &&
+bool StreamId::IsLegalMidName(rtc::ArrayView<const char> name) {
+  return ::webrtc::IsLegalMidName(absl::string_view(name.data(), name.size()));
+}
+
+bool IsLegalRsidName(absl::string_view name) {
+  return (name.size() <= kMidRsidMaxSize && name.size() > 0 &&
           std::all_of(name.data(), name.data() + name.size(), isalnum));
 }
 
+bool StreamId::IsLegalRsidName(rtc::ArrayView<const char> name) {
+  return ::webrtc::IsLegalRsidName(absl::string_view(name.data(), name.size()));
+}
+
 void StreamId::Set(const char* data, size_t size) {
   // If |data| contains \0, the stream id size might become less than |size|.
   RTC_CHECK_LE(size, kMaxSize);
diff --git a/modules/rtp_rtcp/include/rtp_rtcp_defines.h b/modules/rtp_rtcp/include/rtp_rtcp_defines.h
index a4e75ba..d339ecb 100644
--- a/modules/rtp_rtcp/include/rtp_rtcp_defines.h
+++ b/modules/rtp_rtcp/include/rtp_rtcp_defines.h
@@ -15,6 +15,7 @@
 #include <list>
 #include <vector>
 
+#include "absl/strings/string_view.h"
 #include "absl/types/variant.h"
 #include "api/audio_codecs/audio_format.h"
 #include "api/rtp_headers.h"
@@ -45,6 +46,9 @@
 
 enum StorageType { kDontRetransmit, kAllowRetransmission };
 
+bool IsLegalMidName(absl::string_view name);
+bool IsLegalRsidName(absl::string_view name);
+
 // This enum must not have any gaps, i.e., all integers between
 // kRtpExtensionNone and kRtpExtensionNumberOfExtensions must be valid enum
 // entries.