Ensure the SRT file matches your video source (usually 24fps for modern restorations or 25fps for PAL region formats).
To help you find exactly what you need for your viewing experience, let me know:
To find or use subtitles for Alfred Hitchcock's Blackmail (1929)
Before searching for subtitle files, you must know which version of the film you have. In 1929, studios were terrified of the new sound-on-film technology. Hitchcock shot Blackmail as a silent film. Halfway through production, the studio ordered him to convert it into a talkie.