This is, I think, one of the most purely French moments ever caught on film, and a revelation if you have only ever heard the recording. Live, Piaf is like some kind of Gallic blues-shouter. She is sick, old, raddled, exhausted - and feral, terrifying, seductive, genius.
Her effect on the audience can be gauged by the storm of an ovation that ends the clip, all the more amazing when you see how she is literally holding herself up, clutching the stage curtain.
For the rather more sedate version peddled, a few years earlier, to American audiences on the Ed Sullivan show (and an example of Piaf's charming way with English), you might watch this clip. But here we see the real, untrammeled, tragic/triumphant thing.