The flagpoles at the end of each level in Super Mario Bros are rewarding when you're playing the game, but if you're setting up a TAS they suddenly become infuriating wastes of time. This video will show you how to TAS skip the flagpoles, which should improve your time substantially.
From the Creator:
In this tutorial, I show you how to both go through some blocks and how to basically do the skip. To go through certain blocks, find the first frame where when Mario jumps, he will not land on top of the block but will half go through it. Hold left once you find it, and depending on the block and the angle and pixel positioning Mario may go through a little or may go all the way through
As for the pole, jump from a decently high distance with running speed. Hold a for a few frames until the first frame where Mario would land on top of the block. Now hold left for 1 frame for positioning. Now, test frames until you find the first frame where when you are holding right, Mario will not land on the block but slightly enter it. Once you are about to go through, hold left and right when Mario lands, hold left, b and a. for 1 frame. then release all input and you should get it.