diff --git a/aegisub/libffms/src/core/lavfvideo.cpp b/aegisub/libffms/src/core/lavfvideo.cpp
index e62a02c7d..07bc40746 100644
--- a/aegisub/libffms/src/core/lavfvideo.cpp
+++ b/aegisub/libffms/src/core/lavfvideo.cpp
@@ -67,6 +67,12 @@ FFLAVFVideo::FFLAVFVideo(const char *SourceFile, int Track, FFMS_Index *Index,
 	VP.FPSNumerator = FormatContext->streams[VideoTrack]->time_base.den;
 	VP.RFFDenominator = CodecContext->time_base.num;
 	VP.RFFNumerator = CodecContext->time_base.den;
+	if (CodecContext->codec_id == CODEC_ID_H264) {
+		if (VP.RFFNumerator & 1)
+			VP.RFFDenominator *= 2;
+		else
+			VP.RFFNumerator /= 2;
+	}
 	VP.NumFrames = Frames.size();
 	VP.TopFieldFirst = DecodeFrame->top_field_first;
 #ifdef FFMS_HAVE_FFMPEG_COLORSPACE_INFO
@@ -115,12 +121,18 @@ void FFLAVFVideo::DecodeNextFrame(int64_t *AStartTime) {
 			if (*AStartTime < 0)
 				*AStartTime = Packet.dts;
 
-			if (CodecContext->codec_id == CODEC_ID_MPEG4 && IsNVOP(Packet)) {
-				av_free_packet(&Packet);
-				goto Done;
-			}
-
 			avcodec_decode_video2(CodecContext, DecodeFrame, &FrameFinished, &Packet);
+
+			if (CodecContext->codec_id == CODEC_ID_MPEG4) {
+				if (IsPackedFrame(Packet)) {
+					MPEG4Counter++;
+				} else if (IsNVOP(Packet) && MPEG4Counter && FrameFinished) {
+					MPEG4Counter--;
+				} else if (IsNVOP(Packet) && !MPEG4Counter && !FrameFinished) {
+					av_free_packet(&Packet);
+					goto Done;
+				}
+			}
         }
 
         av_free_packet(&Packet);
@@ -184,6 +196,7 @@ ReSeek:
 
 		if (HasSeeked) {
 			HasSeeked = false;
+			MPEG4Counter = 0;
 
 			// Is the seek destination time known? Does it belong to a frame?
 			if (StartTime < 0 || (CurrentFrame = Frames.FrameFromPTS(StartTime)) < 0) {
diff --git a/aegisub/libffms/src/core/matroskavideo.cpp b/aegisub/libffms/src/core/matroskavideo.cpp
index d45c95a8f..a815c6fac 100644
--- a/aegisub/libffms/src/core/matroskavideo.cpp
+++ b/aegisub/libffms/src/core/matroskavideo.cpp
@@ -98,6 +98,12 @@ FFMatroskaVideo::FFMatroskaVideo(const char *SourceFile, int Track,
 	VP.FPSNumerator = 30;
 	VP.RFFDenominator = CodecContext->time_base.num;
 	VP.RFFNumerator = CodecContext->time_base.den;
+	if (CodecContext->codec_id == CODEC_ID_H264) {
+		if (VP.RFFNumerator & 1)
+			VP.RFFDenominator *= 2;
+		else
+			VP.RFFNumerator /= 2;
+	}
 	VP.NumFrames = Frames.size();
 	VP.TopFieldFirst = DecodeFrame->top_field_first;
 #ifdef FFMS_HAVE_FFMPEG_COLORSPACE_INFO
@@ -159,11 +165,18 @@ void FFMatroskaVideo::DecodeNextFrame() {
 
 		PacketNumber++;
 
-		if (CodecContext->codec_id == CODEC_ID_MPEG4 && IsNVOP(Packet))
-			goto Done;
-
 		avcodec_decode_video2(CodecContext, DecodeFrame, &FrameFinished, &Packet);
 
+		if (CodecContext->codec_id == CODEC_ID_MPEG4) {
+			if (IsPackedFrame(Packet)) {
+				MPEG4Counter++;
+			} else if (IsNVOP(Packet) && MPEG4Counter && FrameFinished) {
+				MPEG4Counter--;
+			} else if (IsNVOP(Packet) && !MPEG4Counter && !FrameFinished) {
+				goto Done;
+			}
+		}
+
 		if (FrameFinished)
 			goto Done;
 	}
@@ -190,6 +203,7 @@ FFMS_Frame *FFMatroskaVideo::GetFrame(int n) {
 
 	int ClosestKF = Frames.FindClosestVideoKeyFrame(n);
 	if (CurrentFrame > n || ClosestKF > CurrentFrame + 10) {
+		MPEG4Counter = 0;
 		PacketNumber = ClosestKF;
 		CurrentFrame = ClosestKF;
 		avcodec_flush_buffers(CodecContext);
diff --git a/aegisub/libffms/src/core/utils.cpp b/aegisub/libffms/src/core/utils.cpp
index 061765bdb..9c0c31a87 100644
--- a/aegisub/libffms/src/core/utils.cpp
+++ b/aegisub/libffms/src/core/utils.cpp
@@ -202,8 +202,17 @@ void InitNullPacket(AVPacket &pkt) {
 	pkt.size = 0;
 }
 
+bool IsPackedFrame(AVPacket &pkt) {
+	for (int i = 0; i < pkt.size - 5; i++)
+		if (pkt.data[i] == 0x00 && pkt.data[i + 1] == 0x00 && pkt.data[i + 2] == 0x01 && pkt.data[i + 3] == 0xB6 && (pkt.data[i + 4] & 0x40))
+			for (i = i + 5; i < pkt.size - 5; i++)
+				if (pkt.data[i] == 0x00 && pkt.data[i + 1] == 0x00 && pkt.data[i + 2] == 0x01 && pkt.data[i + 3] == 0xB6 && (pkt.data[i + 4] & 0xC0) == 0x80)
+					return true;
+	return false;
+}
+
 bool IsNVOP(AVPacket &pkt) {
-	const uint8_t MPEG4NVOP[] = { 0x00, 0x00, 0x01, 0xB6 };
+	static const uint8_t MPEG4NVOP[] = { 0x00, 0x00, 0x01, 0xB6 };
 	return (pkt.size >= 4 && pkt.size <= 8) && !memcmp(pkt.data, MPEG4NVOP, 4);
 }
 
diff --git a/aegisub/libffms/src/core/utils.h b/aegisub/libffms/src/core/utils.h
index 5145c90a9..0e377fe06 100644
--- a/aegisub/libffms/src/core/utils.h
+++ b/aegisub/libffms/src/core/utils.h
@@ -142,6 +142,7 @@ FFMS_TrackType HaaliTrackTypeToFFTrackType(int TT);
 void ReadFrame(uint64_t FilePos, unsigned int &FrameSize, CompressedStream *CS, MatroskaReaderContext &Context);
 bool AudioFMTIsFloat(SampleFormat FMT);
 void InitNullPacket(AVPacket &pkt);
+bool IsPackedFrame(AVPacket &pkt);
 bool IsNVOP(AVPacket &pkt);
 void FillAP(FFMS_AudioProperties &AP, AVCodecContext *CTX, FFMS_Track &Frames);
 #ifdef HAALISOURCE
diff --git a/aegisub/libffms/src/core/videosource.cpp b/aegisub/libffms/src/core/videosource.cpp
index cf03d76cd..45e1230b1 100644
--- a/aegisub/libffms/src/core/videosource.cpp
+++ b/aegisub/libffms/src/core/videosource.cpp
@@ -162,6 +162,7 @@ FFMS_VideoSource::FFMS_VideoSource(const char *SourceFile, FFMS_Index *Index, in
 	SWS = NULL;
 	LastFrameNum = 0;
 	CurrentFrame = 1;
+	MPEG4Counter = 0;
 	CodecContext = NULL;
 	LastFrameHeight = -1;
 	LastFrameWidth = -1;
diff --git a/aegisub/libffms/src/core/videosource.h b/aegisub/libffms/src/core/videosource.h
index 70d25a745..bf09a919a 100644
--- a/aegisub/libffms/src/core/videosource.h
+++ b/aegisub/libffms/src/core/videosource.h
@@ -73,6 +73,7 @@ protected:
 	FFMS_Track Frames;
 	int VideoTrack;
 	int	CurrentFrame;
+	int MPEG4Counter;
 	AVCodecContext *CodecContext;
 
 	FFMS_VideoSource(const char *SourceFile, FFMS_Index *Index, int Track);