diff --git a/dom/media/mediasource/TrackBuffersManager.cpp b/dom/media/mediasource/TrackBuffersManager.cpp
index b552adf291..5e40a977d9 100644
--- a/dom/media/mediasource/TrackBuffersManager.cpp
+++ b/dom/media/mediasource/TrackBuffersManager.cpp
@@ -31,6 +31,7 @@ mozilla::LogModule* GetMediaSourceSamplesLog()
   return sLogModule;
 }
 #define SAMPLE_DEBUG(arg, ...) MOZ_LOG(GetMediaSourceSamplesLog(), mozilla::LogLevel::Debug, ("TrackBuffersManager(%p)::%s: " arg, this, __func__, ##__VA_ARGS__))
+#define SAMPLE_DEBUGV(arg, ...) MOZ_LOG(GetMediaSourceSamplesLog(), mozilla::LogLevel::Verbose, ("TrackBuffersManager(%p)::%s: " arg, this, __func__, ##__VA_ARGS__))
 
 namespace mozilla {
 
@@ -708,7 +709,11 @@ TrackBuffersManager::SegmentParserLoop()
       if (mNewMediaSegmentStarted) {
         if (NS_SUCCEEDED(newData) && mLastParsedEndTime.isSome() &&
             start < mLastParsedEndTime.ref().ToMicroseconds()) {
-          MSE_DEBUG("Re-creating demuxer");
+          MSE_DEBUG("Re-creating demuxer, new start (%" PRId64
+                    ") is smaller than last parsed end time (%" PRId64 ")",
+                    start,
+                    mLastParsedEndTime.value());
+          mFrameEndTimeBeforeRecreateDemuxer = Some(end);
           ResetDemuxingState();
           return;
         }
@@ -817,7 +822,15 @@ TrackBuffersManager::CreateDemuxerforMIMEType()
       mType.LowerCaseEqualsLiteral("video/x-matroska") ||
       mType.LowerCaseEqualsLiteral("audio/x-matroska") ||
       mType.LowerCaseEqualsLiteral("audio/webm")) {
-    mInputDemuxer = new WebMDemuxer(mCurrentInputBuffer, true /* IsMediaSource*/ );
+    if (mFrameEndTimeBeforeRecreateDemuxer) {
+      MSE_DEBUG(
+          "CreateDemuxerFromMimeType: "
+          "mFrameEndTimeBeforeRecreateDemuxer=%" PRId64,
+          mFrameEndTimeBeforeRecreateDemuxer.value());
+    }
+    mInputDemuxer = new WebMDemuxer(mCurrentInputBuffer, true /* IsMediaSource*/,
+                                    mFrameEndTimeBeforeRecreateDemuxer);
+    mFrameEndTimeBeforeRecreateDemuxer.reset();
     return;
   }
 
@@ -825,6 +838,7 @@ TrackBuffersManager::CreateDemuxerforMIMEType()
   if (mType.LowerCaseEqualsLiteral("video/mp4") ||
       mType.LowerCaseEqualsLiteral("audio/mp4")) {
     mInputDemuxer = new MP4Demuxer(mCurrentInputBuffer);
+    mFrameEndTimeBeforeRecreateDemuxer.reset();
     return;
   }
 #endif
@@ -1229,9 +1243,11 @@ void
 TrackBuffersManager::OnVideoDemuxCompleted(RefPtr<MediaTrackDemuxer::SamplesHolder> aSamples)
 {
   MOZ_ASSERT(OnTaskQueue());
-  MSE_DEBUG("%d video samples demuxed", aSamples->mSamples.Length());
   mVideoTracks.mDemuxRequest.Complete();
   mVideoTracks.mQueuedSamples.AppendElements(aSamples->mSamples);
+  MSE_DEBUG("%zu video samples demuxed, queued-sz=%zu",
+            aSamples->mSamples.Length(),
+            mVideoTracks.mQueuedSamples.Length());
   DoDemuxAudio();
 }
 
@@ -1472,6 +1488,9 @@ TrackBuffersManager::ProcessFrames(TrackBuffer& aSamples, TrackData& aTrackData)
     if (trackBuffer.mNeedRandomAccessPoint) {
       // 1. If the coded frame is not a random access point, then drop the coded frame and jump to the top of the loop to start processing the next coded frame.
       if (!sample->mKeyframe) {
+        SAMPLE_DEBUGV("skipping sample [%" PRId64 ",%" PRId64 "]",
+                      sample->mTime,
+                      sample->GetEndTime());
         continue;
       }
       // 2. Set the need random access point flag on track buffer to false.
@@ -1532,6 +1551,7 @@ TrackBuffersManager::ProcessFrames(TrackBuffer& aSamples, TrackData& aTrackData)
         // 3. Unset the last frame duration on all track buffers.
         // 4. Unset the highest end timestamp on all track buffers.
         // 5. Set the need random access point flag on all track buffers to true.
+        MSE_DEBUG("Resetting append state");
         track->ResetAppendState();
       }
       // 6. Jump to the Loop Top step above to restart processing of the current coded frame.
@@ -1930,10 +1950,12 @@ TrackBuffersManager::RecreateParser(bool aReuseInitData)
   // we can optimize this part. TODO
   mParser = ContainerParser::CreateForMIMEType(mType);
   if (aReuseInitData && mInitData) {
+    MSE_DEBUG("Using existing init data to reset parser");
     int64_t start, end;
     mParser->ParseStartAndEndTimestamps(mInitData, start, end);
     mProcessedInput = mInitData->Length();
   } else {
+    MSE_DEBUG("Resetting parser, not reusing init data");
     mProcessedInput = 0;
   }
 }
diff --git a/dom/media/mediasource/TrackBuffersManager.h b/dom/media/mediasource/TrackBuffersManager.h
index 11bcb353ab..7bd2131bce 100644
--- a/dom/media/mediasource/TrackBuffersManager.h
+++ b/dom/media/mediasource/TrackBuffersManager.h
@@ -492,6 +492,8 @@ private:
   media::TimeIntervals mAudioBufferedRanges;
   // MediaInfo of the first init segment read.
   MediaInfo mInfo;
+  
+  Maybe<int64_t> mFrameEndTimeBeforeRecreateDemuxer;
 };
 
 } // namespace mozilla
diff --git a/dom/media/webm/NesteggPacketHolder.h b/dom/media/webm/NesteggPacketHolder.h
index 00a7b12cfb..0f8f9b63ab 100644
--- a/dom/media/webm/NesteggPacketHolder.h
+++ b/dom/media/webm/NesteggPacketHolder.h
@@ -22,10 +22,11 @@ public:
     : mPacket(nullptr)
     , mOffset(-1)
     , mTimestamp(-1)
+    , mDefaultDuration(-1)
     , mDuration(-1)
     , mIsKeyframe(false) {}
 
-  bool Init(nestegg_packet* aPacket, int64_t aOffset, unsigned aTrack, bool aIsKeyframe)
+  bool Init(nestegg_packet* aPacket, nestegg* aContext, int64_t aOffset, unsigned aTrack, bool aIsKeyframe)
   {
     uint64_t timestamp_ns;
     if (nestegg_packet_tstamp(aPacket, &timestamp_ns) == -1) {
@@ -44,6 +45,9 @@ public:
     if (!nestegg_packet_duration(aPacket, &duration_ns)) {
       mDuration = duration_ns / 1000;
     }
+    if (!nestegg_track_default_duration(aContext, mTrack, &duration_ns)) {
+      mDefaultDuration = duration_ns / 1000;
+    }
     return true;
   }
 
@@ -51,6 +55,7 @@ public:
   int64_t Offset() { MOZ_ASSERT(IsInitialized()); return mOffset; }
   int64_t Timestamp() { MOZ_ASSERT(IsInitialized()); return mTimestamp; }
   int64_t Duration() { MOZ_ASSERT(IsInitialized()); return mDuration; }
+  int64_t DefaultDuration() const { MOZ_ASSERT(IsInitialized()); return mDefaultDuration; }
   unsigned Track() { MOZ_ASSERT(IsInitialized()); return mTrack; }
   bool IsKeyframe() { MOZ_ASSERT(IsInitialized()); return mIsKeyframe; }
 
@@ -60,7 +65,7 @@ private:
     nestegg_free_packet(mPacket);
   }
 
-  bool IsInitialized() { return mOffset >= 0; }
+  bool IsInitialized() const { return mOffset >= 0; }
 
   nestegg_packet* mPacket;
 
@@ -72,8 +77,13 @@ private:
   int64_t mTimestamp;
 
   // Packet duration in microseconds; -1 if unknown or retrieval failed.
+  // https://www.webmproject.org/docs/container/#BlockDuration
   int64_t mDuration;
 
+  // Default duration in microseconds; -1 if unknown or retrieval failed.
+  // https://www.webmproject.org/docs/container/#Duration
+  int64_t mDefaultDuration;
+
   // Track ID.
   unsigned mTrack;
 
diff --git a/dom/media/webm/WebMDemuxer.cpp b/dom/media/webm/WebMDemuxer.cpp
index 1009fedc69..fc98db4d77 100644
--- a/dom/media/webm/WebMDemuxer.cpp
+++ b/dom/media/webm/WebMDemuxer.cpp
@@ -17,6 +17,7 @@
 #include "gfx2DGlue.h"
 #include "mozilla/Atomics.h"
 #include "mozilla/EndianUtils.h"
+#include "mozilla/Maybe.h"
 #include "mozilla/SharedThreadPool.h"
 #include "MediaDataDemuxer.h"
 #include "nsAutoPtr.h"
@@ -158,7 +159,9 @@ WebMDemuxer::WebMDemuxer(MediaResource* aResource)
 {
 }
 
-WebMDemuxer::WebMDemuxer(MediaResource* aResource, bool aIsMediaSource)
+WebMDemuxer::WebMDemuxer(MediaResource* aResource,
+                         bool aIsMediaSource,
+                         Maybe<int64_t> aFrameEndTimeBeforeRecreateDemuxer)
   : mVideoContext(this, aResource)
   , mAudioContext(this, aResource)
   , mBufferedState(nullptr)
@@ -174,6 +177,13 @@ WebMDemuxer::WebMDemuxer(MediaResource* aResource, bool aIsMediaSource)
   , mLastWebMBlockOffset(-1)
   , mIsMediaSource(aIsMediaSource)
 {
+  MOZ_ASSERT_IF(!aIsMediaSource,
+                aFrameEndTimeBeforeRecreateDemuxer.isNothing());
+  if (aIsMediaSource && aFrameEndTimeBeforeRecreateDemuxer) {
+    mVideoFrameEndTimeBeforeReset = aFrameEndTimeBeforeRecreateDemuxer;
+    WEBM_DEBUG("Set mVideoFrameEndTimeBeforeReset=%" PRId64,
+               mVideoFrameEndTimeBeforeReset.value());
+  }
 }
 
 WebMDemuxer::~WebMDemuxer()
@@ -592,6 +602,11 @@ WebMDemuxer::GetNextPacket(TrackInfo::TrackType aType, MediaRawDataQueue *aSampl
   }
   int64_t tstamp = holder->Timestamp();
   int64_t duration = holder->Duration();
+  int64_t defaultDuration = holder->DefaultDuration();
+  if (aType == TrackInfo::TrackType::kVideoTrack) {
+    WEBM_DEBUG("GetNextPacket(video): tstamp=%" PRId64 ", duration=%" PRId64, ", defaultDuration=%" PRId64,
+               tstamp, duration, defaultDuration);
+  }
 
   // The end time of this frame is the start time of the next frame. Fetch
   // the timestamp of the next packet for this track.  If we've reached the
@@ -632,6 +647,12 @@ WebMDemuxer::GetNextPacket(TrackInfo::TrackType aType, MediaRawDataQueue *aSampl
                (mIsMediaSource && mLastVideoFrameTime.isSome())) {
       next_tstamp = tstamp;
       next_tstamp += tstamp - mLastVideoFrameTime.refOr(0);
+    } else if (defaultDuration >= 0) {
+      next_tstamp = tstamp + defaultDuration;
+    } else if (mVideoFrameEndTimeBeforeReset) {
+      WEBM_DEBUG("Setting next timestamp to be %" PRId64 " us",
+                 mVideoFrameEndTimeBeforeReset.value());
+      next_tstamp = mVideoFrameEndTimeBeforeReset.ref();
     } else {
       PushVideoPacket(holder);
     }
@@ -865,7 +886,7 @@ WebMDemuxer::DemuxPacket(TrackInfo::TrackType aType,
 
   int64_t offset = Resource(aType).Tell();
   RefPtr<NesteggPacketHolder> holder = new NesteggPacketHolder();
-  if (!holder->Init(packet, offset, track, false)) {
+  if (!holder->Init(packet, Context(aType), offset, track, false)) {
     return NS_ERROR_DOM_MEDIA_DEMUXER_ERR;
   }
 
diff --git a/dom/media/webm/WebMDemuxer.h b/dom/media/webm/WebMDemuxer.h
index a0d2960d33..99d516b632 100644
--- a/dom/media/webm/WebMDemuxer.h
+++ b/dom/media/webm/WebMDemuxer.h
@@ -92,7 +92,9 @@ public:
   explicit WebMDemuxer(MediaResource* aResource);
   // Indicate if the WebMDemuxer is to be used with MediaSource. In which
   // case the demuxer will stop reads to the last known complete block.
-  WebMDemuxer(MediaResource* aResource, bool aIsMediaSource);
+  WebMDemuxer(MediaResource* aResource,
+              bool aIsMediaSource,
+              Maybe<int64_t> aFrameEndTimeBeforeRecreateDemuxer = Nothing());
   
   RefPtr<InitPromise> Init() override;
 
@@ -227,6 +229,8 @@ private:
   Maybe<int64_t> mLastAudioFrameTime;
   Maybe<int64_t> mLastVideoFrameTime;
 
+  Maybe<int64_t> mVideoFrameEndTimeBeforeReset;
+
   // Codec ID of audio track
   int mAudioCodec;
   // Codec ID of video track
diff --git a/dom/script/ScriptLoader.cpp b/dom/script/ScriptLoader.cpp
index a61ba92c23..cbe4265181 100644
--- a/dom/script/ScriptLoader.cpp
+++ b/dom/script/ScriptLoader.cpp
@@ -1307,9 +1307,8 @@ ScriptLoader::StartLoad(ScriptLoadRequest *aRequest, const nsAString &aType,
     // According to the spec, module scripts have different behaviour to classic
     // scripts and always use CORS.
     securityFlags = nsILoadInfo::SEC_REQUIRE_CORS_DATA_INHERITS;
-    if (aRequest->CORSMode() == CORS_NONE) {
-      securityFlags |= nsILoadInfo::SEC_COOKIES_OMIT;
-    } else if (aRequest->CORSMode() == CORS_ANONYMOUS) {
+    if (aRequest->CORSMode() == CORS_NONE ||
+        aRequest->CORSMode() == CORS_ANONYMOUS) {
       securityFlags |= nsILoadInfo::SEC_COOKIES_SAME_ORIGIN;
     } else {
       MOZ_ASSERT(aRequest->CORSMode() == CORS_USE_CREDENTIALS);
diff --git a/layout/media/symbols.def.in b/layout/media/symbols.def.in
index d81b199d05..101e98d6fd 100644
--- a/layout/media/symbols.def.in
+++ b/layout/media/symbols.def.in
@@ -27,6 +27,7 @@ nestegg_track_codec_data_count
 nestegg_track_codec_id
 nestegg_track_content_enc_key_id
 nestegg_track_count
+nestegg_track_default_duration
 nestegg_get_cue_point
 nestegg_track_seek
 nestegg_track_type
diff --git a/media/libjpeg/moz.build b/media/libjpeg/moz.build
index f24b4fcf0f..1068e3f0ff 100644
--- a/media/libjpeg/moz.build
+++ b/media/libjpeg/moz.build
@@ -245,7 +245,7 @@ elif CONFIG['CPU_ARCH'].startswith('ppc'):
         'simd/powerpc/jsimd.c',
     ]
     for srcfile in ppc_vmx_sources:
-        SOURCES[srcfile].flags += CONFIG['PPC_VMX_FLAGS']
+        SOURCES[srcfile].flags += ['-maltivec']
 else: # No SIMD support?
     SOURCES += [
         'jsimd_none.c',
diff --git a/media/libjpeg/simd/powerpc/jsimd.c b/media/libjpeg/simd/powerpc/jsimd.c
index b9e86dcfac..5ff3be48ac 100644
--- a/media/libjpeg/simd/powerpc/jsimd.c
+++ b/media/libjpeg/simd/powerpc/jsimd.c
@@ -38,6 +38,9 @@
 #elif defined(__FreeBSD__)
 #include <machine/cpu.h>
 #include <sys/auxv.h>
+#elif defined(__NetBSD__)
+#include <sys/param.h>
+#include <sys/sysctl.h>
 #endif
 
 static unsigned int simd_support = ~0;
@@ -127,6 +130,9 @@ init_simd(void)
   size_t len = sizeof(altivec);
 #elif defined(__FreeBSD__)
   unsigned long cpufeatures = 0;
+#elif defined(__NetBSD__)
+  int ret, av;
+  size_t len;
 #endif
 
   if (simd_support != ~0U)
@@ -149,6 +155,11 @@ init_simd(void)
 #elif defined(__OpenBSD__)
   if (sysctl(mib, 2, &altivec, &len, NULL, 0) == 0 && altivec != 0)
     simd_support |= JSIMD_ALTIVEC;
+#elif defined(__NetBSD__)
+  len = sizeof(av);
+  ret = sysctlbyname("machdep.altivec", &av, &len, NULL, 0);
+  if (!ret && av)
+    simd_support |= JSIMD_ALTIVEC;
 #elif defined(__FreeBSD__)
   elf_aux_info(AT_HWCAP, &cpufeatures, sizeof(cpufeatures));
   if (cpufeatures & PPC_FEATURE_HAS_ALTIVEC)