The film image thus became almost square during the early years of the talkies until the space occupied by the sound track on the film was successfully reduced.

Can someone explain to me what this mean? I don't understand.

In the early years of films with sound (known as "talkies"), the film image on the screen was almost square in shape. However, there was a challenge in fitting the sound track onto the film alongside the visual image. To address this, filmmakers and engineers worked on reducing the amount of space occupied by the sound track on the film. This means that they found ways to make the sound track take up less physical space on the film strip, allowing for a more balanced and aesthetically pleasing image on the screen.