ACodec: don't enable B frames for AVC by default

The default behavior has been no B-frames for AVC encoders, and it
should stay that way. The explicit setting for enabling the feature
is under discussion.

Bug: 122855205
Test: builds
Change-Id: I76bae5ad78ef9ecbfadecc64c3bd4e9eb8f58011
diff --git a/media/libstagefright/ACodec.cpp b/media/libstagefright/ACodec.cpp
index 52cb5fa..9c46659 100644
--- a/media/libstagefright/ACodec.cpp
+++ b/media/libstagefright/ACodec.cpp
@@ -4431,9 +4431,9 @@
         h264type.nRefFrames = 2;
         h264type.nBFrames = mLatency == 0 ? 1 : std::min(1U, mLatency - 1);
 
-        // disable B-frames until MPEG4Writer can guarantee finalizing files with B-frames
-        // h264type.nRefFrames = 1;
-        // h264type.nBFrames = 0;
+        // disable B-frames until we have explicit settings for enabling the feature.
+        h264type.nRefFrames = 1;
+        h264type.nBFrames = 0;
 
         h264type.nPFrames = setPFramesSpacing(iFrameInterval, frameRate, h264type.nBFrames);
         h264type.nAllowedPictureTypes =