+/**
+ * Utility function to access log2_chroma_w log2_chroma_h from
+ * the pixel format AVPixFmtDescriptor.
+ *
+ * This function asserts that pix_fmt is valid. See av_pix_fmt_get_chroma_sub_sample
+ * for one that returns a failure code and continues in case of invalid
+ * pix_fmts.
+ *
+ * @param[in] pix_fmt the pixel format
+ * @param[out] h_shift store log2_chroma_h
+ * @param[out] v_shift store log2_chroma_w
+ *
+ * @see av_pix_fmt_get_chroma_sub_sample
+ */
+