--- a/content/media/webm/EbmlComposer.cpp
+++ b/content/media/webm/EbmlComposer.cpp
@@ -33,27 +33,24 @@ void EbmlComposer::GenerateHeader()
       Ebml_StartSubElement(&ebml, &ebmlLocseg, SeekHead);
       // Todo: We don't know the exact sizes of encoded data and ignore this section.
       Ebml_EndSubElement(&ebml, &ebmlLocseg);
       writeSegmentInformation(&ebml, &ebmlLoc, TIME_CODE_SCALE, 0);
       {
         EbmlLoc trackLoc;
         Ebml_StartSubElement(&ebml, &trackLoc, Tracks);
         {
-          char cid_string[8];
           // Video
           if (mWidth > 0 && mHeight > 0) {
-            strcpy(cid_string, "V_VP8");
-            writeVideoTrack(&ebml, 0x1, 0, cid_string,
+            writeVideoTrack(&ebml, 0x1, 0, "V_VP8",
                             mWidth, mHeight, mFrameRate);
           }
           // Audio
           if (mCodecPrivateData.Length() > 0) {
-            strcpy(cid_string, "A_VORBIS");
-            writeAudioTrack(&ebml, 0x2, 0x0, cid_string, mSampleFreq,
+            writeAudioTrack(&ebml, 0x2, 0x0, "A_VORBIS", mSampleFreq,
                             mChannels, mCodecPrivateData.Elements(),
                             mCodecPrivateData.Length());
           }
         }
         Ebml_EndSubElement(&ebml, &trackLoc);
       }
     }
     // The Recording length is unknow and ignore write the whole Segment element size

--- a/media/libmkv/WebMElement.c
+++ b/media/libmkv/WebMElement.c
@@ -51,17 +51,17 @@ static UInt64 generateTrackID(unsigned i
   UInt64 r = rand();
   r = r << 32;
   r +=  rand();
 //  UInt64 rval = t ^ r;
   return t ^ r;
 }
 
 void writeVideoTrack(EbmlGlobal *glob, unsigned int trackNumber, int flagLacing,
-                     char *codecId, unsigned int pixelWidth, unsigned int pixelHeight,
+                     const char *codecId, unsigned int pixelWidth, unsigned int pixelHeight,
                      double frameRate) {
   EbmlLoc start;
   UInt64 trackID;
   Ebml_StartSubElement(glob, &start, TrackEntry);
   Ebml_SerializeUnsigned(glob, TrackNumber, trackNumber);
   trackID = generateTrackID(trackNumber);
   Ebml_SerializeUnsigned(glob, TrackUID, trackID);
   Ebml_SerializeString(glob, CodecName, "VP8");  // TODO shouldn't be fixed
@@ -74,17 +74,17 @@ void writeVideoTrack(EbmlGlobal *glob, u
     Ebml_SerializeUnsigned(glob, PixelWidth, pixelWidth);
     Ebml_SerializeUnsigned(glob, PixelHeight, pixelHeight);
     Ebml_SerializeFloat(glob, FrameRate, frameRate);
     Ebml_EndSubElement(glob, &videoStart); // Video
   }
   Ebml_EndSubElement(glob, &start); // Track Entry
 }
 void writeAudioTrack(EbmlGlobal *glob, unsigned int trackNumber, int flagLacing,
-                     char *codecId, double samplingFrequency, unsigned int channels,
+                     const char *codecId, double samplingFrequency, unsigned int channels,
                      unsigned char *private, unsigned long privateSize) {
   EbmlLoc start;
   UInt64 trackID;
   Ebml_StartSubElement(glob, &start, TrackEntry);
   Ebml_SerializeUnsigned(glob, TrackNumber, trackNumber);
   trackID = generateTrackID(trackNumber);
   Ebml_SerializeUnsigned(glob, TrackUID, trackID);
   Ebml_SerializeUnsigned(glob, TrackType, 2); // audio is always 2

--- a/media/libmkv/WebMElement.h
+++ b/media/libmkv/WebMElement.h
@@ -15,20 +15,20 @@ extern "C" {
 
 #include "EbmlWriter.h"
 
 // these are helper functions
 void writeHeader(EbmlGlobal *ebml);
 void writeSegmentInformation(EbmlGlobal *ebml, EbmlLoc *startInfo, unsigned long timeCodeScale, double duration);
 // this function is a helper only, it assumes a lot of defaults
 void writeVideoTrack(EbmlGlobal *ebml, unsigned int trackNumber, int flagLacing,
-                     char *codecId, unsigned int pixelWidth, unsigned int pixelHeight,
+                     const char *codecId, unsigned int pixelWidth, unsigned int pixelHeight,
                      double frameRate);
 void writeAudioTrack(EbmlGlobal *glob, unsigned int trackNumber, int flagLacing,
-                     char *codecId, double samplingFrequency, unsigned int channels,
+                     const char *codecId, double samplingFrequency, unsigned int channels,
                      unsigned char *private_, unsigned long privateSize);
 
 void writeSimpleBlock(EbmlGlobal *ebml, unsigned char trackNumber, short timeCode,
                       int isKeyframe, unsigned char lacingFlag, int discardable,
                       unsigned char *data, unsigned long dataLength);
 
 #endif
 

new file mode 100644
--- /dev/null
+++ b/media/libmkv/const_fix.patch
@@ -0,0 +1,37 @@
+diff --git a/WebMElement.c b/WebMElement.c
+--- a/WebMElement.c
++++ b/WebMElement.c
+@@ -56,7 +56,7 @@
+ }
+ 
+ void writeVideoTrack(EbmlGlobal *glob, unsigned int trackNumber, int flagLacing,
+-                     char *codecId, unsigned int pixelWidth, unsigned int pixelHeight,
++                     const char *codecId, unsigned int pixelWidth, unsigned int pixelHeight,
+                      double frameRate) {
+   EbmlLoc start;
+   UInt64 trackID;
+@@ -79,7 +79,7 @@
+   Ebml_EndSubElement(glob, &start); // Track Entry
+ }
+ void writeAudioTrack(EbmlGlobal *glob, unsigned int trackNumber, int flagLacing,
+-                     char *codecId, double samplingFrequency, unsigned int channels,
++                     const char *codecId, double samplingFrequency, unsigned int channels,
+                      unsigned char *private, unsigned long privateSize) {
+   EbmlLoc start;
+   UInt64 trackID;
+diff --git a/WebMElement.h b/WebMElement.h
+--- a/WebMElement.h
++++ b/WebMElement.h
+@@ -20,10 +20,10 @@
+ void writeSegmentInformation(EbmlGlobal *ebml, EbmlLoc *startInfo, unsigned long timeCodeScale, double duration);
+ // this function is a helper only, it assumes a lot of defaults
+ void writeVideoTrack(EbmlGlobal *ebml, unsigned int trackNumber, int flagLacing,
+-                     char *codecId, unsigned int pixelWidth, unsigned int pixelHeight,
++                     const char *codecId, unsigned int pixelWidth, unsigned int pixelHeight,
+                      double frameRate);
+ void writeAudioTrack(EbmlGlobal *glob, unsigned int trackNumber, int flagLacing,
+-                     char *codecId, double samplingFrequency, unsigned int channels,
++                     const char *codecId, double samplingFrequency, unsigned int channels,
+                      unsigned char *private_, unsigned long privateSize);
+ 
+ void writeSimpleBlock(EbmlGlobal *ebml, unsigned char trackNumber, short timeCode,