CCodec: use known default format for bytebuffer mode decoder

Bug: 181386257
Test: manual
Change-Id: Iaadc1eacd9b4f87d14d9bdef62844a90cd829888
diff --git a/media/codec2/sfplugin/CCodec.cpp b/media/codec2/sfplugin/CCodec.cpp
index 60c5901..b203d24 100644
--- a/media/codec2/sfplugin/CCodec.cpp
+++ b/media/codec2/sfplugin/CCodec.cpp
@@ -996,7 +996,15 @@
                 // needed for decoders.
                 if (!(config->mDomain & Config::IS_ENCODER)) {
                     if (surface == nullptr) {
-                        format = flexPixelFormat.value_or(COLOR_FormatYUV420Flexible);
+                        const char *prefix = "";
+                        if (flexSemiPlanarPixelFormat) {
+                            format = COLOR_FormatYUV420SemiPlanar;
+                            prefix = "semi-";
+                        } else {
+                            format = COLOR_FormatYUV420Planar;
+                        }
+                        ALOGD("Client requested ByteBuffer mode decoder w/o color format set: "
+                                "using default %splanar color format", prefix);
                     } else {
                         format = COLOR_FormatSurface;
                     }