--- a/media/libstagefright/binding/MP4Metadata.cpp
+++ b/media/libstagefright/binding/MP4Metadata.cpp
@@ -138,16 +138,20 @@ MP4Metadata::GetNumberTracks(mozilla::Tr
 {
 #ifdef MOZ_RUST_MP4PARSE
   static LazyLogModule sLog("MP4Metadata");
   // Try in rust first.
   mRustState.reset(mp4parse_new());
   int32_t rust_mp4parse_success = try_rust(mRustState, mSource);
   Telemetry::Accumulate(Telemetry::MEDIA_RUST_MP4PARSE_SUCCESS,
                         rust_mp4parse_success == 0);
+  if (rust_mp4parse_success < 0) {
+    Telemetry::Accumulate(Telemetry::MEDIA_RUST_MP4PARSE_ERROR_CODE,
+                          -rust_mp4parse_success);
+  }
   uint32_t rust_tracks = mp4parse_get_track_count(mRustState.get());
   MOZ_LOG(sLog, LogLevel::Info, ("rust parser found %u tracks", rust_tracks));
 #endif
   size_t tracks = mPrivate->mMetadataExtractor->countTracks();
   uint32_t total = 0;
   for (size_t i = 0; i < tracks; i++) {
     sp<MetaData> metaData = mPrivate->mMetadataExtractor->getTrackMetaData(i);
 

--- a/toolkit/components/telemetry/Histograms.json
+++ b/toolkit/components/telemetry/Histograms.json
@@ -6027,21 +6027,32 @@
   "DEVTOOLS_DEBUGGER_RDP_REMOTE_RECONFIGURETHREAD_MS": {
     "expires_in_version": "never",
     "kind": "exponential",
     "high": "10000",
     "n_buckets": "1000",
     "description": "The time (in milliseconds) that it took a 'reconfigure thread' request to go round trip."
   },
   "MEDIA_RUST_MP4PARSE_SUCCESS": {
+    "alert_emails": ["giles@mozilla.com", "kinetik@flim.org"],
     "expires_in_version": "50",
     "kind": "boolean",
+    "bug_numbers": [1220885],
     "description": "(Bug 1220885) Whether the rust mp4 demuxer successfully parsed a stream segment.",
     "cpp_guard": "MOZ_RUST_MP4PARSE"
   },
+  "MEDIA_RUST_MP4PARSE_ERROR_CODE": {
+    "alert_emails": ["giles@mozilla.com", "kinetik@flim.org"],
+    "expires_in_version": "50",
+    "kind": "enumerated",
+    "n_values": 32,
+    "bug_numbers": [1238420],
+    "description": "The error code reported when an MP4 parse attempt has failed.",
+    "cpp_guard": "MOZ_RUST_MP4PARSE"
+  },
   "MEDIA_RUST_MP4PARSE_TRACK_MATCH_AUDIO": {
     "alert_emails": ["giles@mozilla.com", "kinetik@flim.org"],
     "expires_in_version": "50",
     "kind": "boolean",
     "bug_numbers": [1231169],
     "description": "Whether rust and stagefight mp4 parser audio track results match.",
     "cpp_guard": "MOZ_RUST_MP4PARSE"
   },