RCA discussed on TechStuff
So that was a pretty primitive approach, but it was how some early talking pictures were made including the first one the jazz singer, which debuted in nineteen twenty seven RCA photo phone used a totally different approach. The sound was recorded in a narrow band on the side of the frame of film. Some actual photo reactive film. The band would be out of you. When the film was put through a projector. There was a frame on a projector that covers up the edges of the film. And the audio track is on one of those edges. The wits of this strip on the side of the film varies with the frequency of the sound. That was record. Id onto the film. So essentially if sound that's transmitted into a microphone, it is turned into an electric signal which in turn is used to treat this this federal to film. So that it has this record of the frequency. It's almost like a wave form if you were to think of that, you know, in the modern sense if you were to look at an audio file on a audio editing software. So then when you're playing it back. You have a bright lamp that shines light through this narrow strip. And you have a photo sell that picks up the light that's coming through, and it generates an electric current that matches the amount of light that's hitting the photo cell, and that signal goes to a pre amplifier, which can then boost the signal strength. So it can go to an amplifier. And then ultimately speakers the lamp for reading this optical sound. And the photo cell are not in the same position. As the projection lamp, though, it just get in the way. So. This is actually it creates something of a challenge. It means that the soundtrack is offset from the actual frames of the film itself. The soundtrack is either running a little ahead or a little behind the action of the film, depending upon the method that was actually used so in playback, it's all synchronized because if you as you put the fell through the right type of projector. The audio track gets read through the audio system at the same time as the video or the film rather the images are being projected through the projection lamp, and I'll get synchronized together so in playback, synchronized. But if you were to look at the film itself, like if you took the film out of the projector, then you held it up to the light. And you saw where the audio track is the audio. You're looking at would not be the audio that occurs in synchronisation with the image. You're looking at the advantage of that approach was..