diff --git a/dom/media/fmp4/MP4Reader.cpp b/dom/media/fmp4/MP4Reader.cpp
index f1df00e8c218..48c15c048d7e 100644
--- a/dom/media/fmp4/MP4Reader.cpp
+++ b/dom/media/fmp4/MP4Reader.cpp
@@ -15,7 +15,10 @@
 #include "Layers.h"
 #include "SharedThreadPool.h"
 #include "mozilla/Preferences.h"
+#include "mozilla/Telemetry.h"
 #include "mozilla/dom/TimeRanges.h"
+#include "mp4_demuxer/AnnexB.h"
+#include "mp4_demuxer/H264.h"
 #include "SharedDecoderManager.h"
 
 #ifdef MOZ_EME
@@ -64,6 +67,28 @@ TrackTypeToStr(TrackType aTrack)
 }
 #endif
 
+bool
+AccumulateSPSTelemetry(const ByteBuffer* aExtradata)
+{
+  SPSData spsdata;
+  if (H264::DecodeSPSFromExtraData(aExtradata, spsdata) &&
+      spsdata.profile_idc && spsdata.level_idc) {
+    // Collect profile_idc values up to 244, otherwise 0 for unknown.
+    Telemetry::Accumulate(Telemetry::VIDEO_DECODED_H264_SPS_PROFILE,
+                          spsdata.profile_idc <= 244 ? spsdata.profile_idc : 0);
+
+    // Make sure level_idc represents a value between levels 1 and 5.2,
+    // otherwise collect 0 for unknown level.
+    Telemetry::Accumulate(Telemetry::VIDEO_DECODED_H264_SPS_LEVEL,
+                          (spsdata.level_idc >= 10 && spsdata.level_idc <= 52) ?
+                          spsdata.level_idc : 0);
+
+    return true;
+  }
+
+  return false;
+}
+
 // MP4Demuxer wants to do various blocking reads, which cause deadlocks while
 // mDemuxerMonitor is held. This stuff should really be redesigned, but we don't
 // have time for that right now. So in order to get proper synchronization while
@@ -114,6 +139,7 @@ MP4Reader::MP4Reader(AbstractMediaDecoder* aDecoder)
   , mLastReportedNumDecodedFrames(0)
   , mLayersBackendType(layers::LayersBackend::LAYERS_NONE)
   , mDemuxerInitialized(false)
+  , mFoundSPSForTelemetry(false)
   , mIsEncrypted(false)
   , mIndexReady(false)
   , mDemuxerMonitor("MP4 Demuxer")
@@ -465,6 +491,11 @@ MP4Reader::ReadMetadata(MediaInfo* aInfo,
     nsresult rv = mVideo.mDecoder->Init();
     NS_ENSURE_SUCCESS(rv, rv);
     mInfo.mVideo.mIsHardwareAccelerated = mVideo.mDecoder->IsHardwareAccelerated();
+
+    // Collect telemetry from h264 AVCC SPS.
+    if (!mFoundSPSForTelemetry) {
+      mFoundSPSForTelemetry = AccumulateSPSTelemetry(video.extra_data);
+    }
   }
 
   // Get the duration, and report it to the decoder if we have it.
@@ -682,6 +713,13 @@ MP4Reader::Update(TrackType aTrack)
 
   if (needInput) {
     MP4Sample* sample = PopSample(aTrack);
+
+    // Collect telemetry from h264 Annex B SPS.
+    if (sample && !mFoundSPSForTelemetry && AnnexB::HasSPS(sample)) {
+      nsRefPtr<ByteBuffer> extradata = AnnexB::ExtractExtraData(sample);
+      mFoundSPSForTelemetry = AccumulateSPSTelemetry(extradata);
+    }
+
     if (sample) {
       decoder.mDecoder->Input(sample);
       if (aTrack == kVideo) {
diff --git a/dom/media/fmp4/MP4Reader.h b/dom/media/fmp4/MP4Reader.h
index 04a1afc28efc..0c894a626d71 100644
--- a/dom/media/fmp4/MP4Reader.h
+++ b/dom/media/fmp4/MP4Reader.h
@@ -260,6 +260,9 @@ private:
   // True if we've read the streams' metadata.
   bool mDemuxerInitialized;
 
+  // True if we've gathered telemetry from an SPS.
+  bool mFoundSPSForTelemetry;
+
   // Synchronized by decoder monitor.
   bool mIsEncrypted;
 
diff --git a/toolkit/components/telemetry/Histograms.json b/toolkit/components/telemetry/Histograms.json
index b76b1a0b4f92..64c74c0a2d1e 100644
--- a/toolkit/components/telemetry/Histograms.json
+++ b/toolkit/components/telemetry/Histograms.json
@@ -5471,6 +5471,18 @@
     "n_values": 244,
     "description": "The H.264 profile number (profile_idc) as extracted from the codecs parameter passed to HTMLMediaElement.canPlayType."
   },
+  "VIDEO_DECODED_H264_SPS_LEVEL": {
+    "expires_in_version": "40",
+    "kind": "enumerated",
+    "n_values": 51,
+    "description": "The H.264 level (level_idc) as extracted from the decoded SPS, from levels 1 (10) to 5.2 (51), with the addition of 0 for unknown values."
+  },
+  "VIDEO_DECODED_H264_SPS_PROFILE": {
+    "expires_in_version": "40",
+    "kind": "enumerated",
+    "n_values": 244,
+    "description": "The H.264 profile number (profile_idc) as extracted from the decoded SPS."
+  },
   "WEBRTC_ICE_FINAL_CONNECTION_STATE": {
     "expires_in_version": "never",
     "kind": "enumerated",