Recommendations

Option 1: Go ConstraintLayout

Option 2:

if still wants to use LinearLayout Please remove relative layout. try the below code, Relplace the image with yours original one i have used placeholder. If still you see the bad UI please share the file @style/MediaButton

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingHorizontal="10dp"
    android:gravity="center">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:gravity="center"
        android:paddingVertical="6dp"
        android:layout_marginTop="12dp"
        android:layout_marginBottom="12dp"
        android:weightSum="5">

        <ImageButton
            android:id="@+id/btnvolumdown"
            android:layout_width="0dp"
            android:layout_height="35dp"
            android:layout_weight="1"
            android:background="@android:drawable/ic_media_next"
            android:contentDescription="Volume Down"
            android:tint="@color/black" />

        <ImageButton
            android:id="@+id/rew"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="@android:drawable/ic_media_previous"
            android:contentDescription="Rewind" />

        <ImageButton
            android:id="@+id/play"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="@android:drawable/ic_media_play"
            android:contentDescription="Play" />

        <ImageButton
            android:id="@+id/ffwd"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="@android:drawable/ic_media_next"
            android:contentDescription="Fast Forward" />

        <ImageButton
            android:id="@+id/btnvolumup"
            android:layout_width="0dp"
            android:layout_height="35dp"
            android:layout_weight="1"
            android:background="@android:drawable/ic_media_pause"
            android:contentDescription="Volume Up" />
    </LinearLayout>

</LinearLayout>