MatroskaExtractor: don't use new buffer unless necessary

When the NAL size length is 4 bytes, we can store the start code in the space
occupied by the NAL size length and avoid allocating a new buffer and copying
the data into it.
Also fix potential memory leak.

Change-Id: I29dd72a0616dfae66ddd7b7f9478678e356df440

1 files changed, 17 insertions, 6 deletions

diff --git a/media/libstagefright/matroska/MatroskaExtractor.cpp b/media/libstagefright/matroska/MatroskaExtractor.cpp
index ff81379..06057d0 100644
--- a/media/libstagefright/matroska/MatroskaExtractor.cpp
+++ b/media/libstagefright/matroska/MatroskaExtractor.cpp
@@ -548,6 +548,7 @@ status_t MatroskaSource::readBlock() {
             mPendingFrames.clear();
 
             mBlockIter.advance();
+            mbuf->release();
             return ERROR_IO;
         }
 
@@ -668,9 +669,11 @@ status_t MatroskaSource::read(
             if (pass == 1) {
                 memcpy(&dstPtr[dstOffset], "\x00\x00\x00\x01", 4);
 
-                memcpy(&dstPtr[dstOffset + 4],
-                       &srcPtr[srcOffset + mNALSizeLen],
-                       NALsize);
+                if (frame != buffer) {
+                    memcpy(&dstPtr[dstOffset + 4],
+                           &srcPtr[srcOffset + mNALSizeLen],
+                           NALsize);
+                }
             }
 
             dstOffset += 4;  // 0x00 00 00 01
@@ -692,7 +695,13 @@ status_t MatroskaSource::read(
         if (pass == 0) {
             dstSize = dstOffset;
 
-            buffer = new MediaBuffer(dstSize);
+            if (dstSize == srcSize && mNALSizeLen == 4) {
+                // In this special case we can re-use the input buffer by substituting
+                // each 4-byte nal size with a 4-byte start code
+                buffer = frame;
+            } else {
+                buffer = new MediaBuffer(dstSize);
+            }
 
             int64_t timeUs;
             CHECK(frame->meta_data()->findInt64(kKeyTime, &timeUs));
@@ -706,8 +715,10 @@ status_t MatroskaSource::read(
         }
     }
 
-    frame->release();
-    frame = NULL;
+    if (frame != buffer) {
+        frame->release();
+        frame = NULL;
+    }
 
     if (targetSampleTimeUs >= 0ll) {
         buffer->meta_data()->setInt64(