Bertrand, until recently INA was like a fortress. Very difficult to enter and nearly impossible to come out from the place with anything unless you paid the price which could be sky high.
However there have been cracks recently and most noticeably when they opened their video archives.
http://www.ina.fr/index.en.html
You can peek inside, lots of free stuff but if you want the full videos you've got to pay the price. But I have not been able to get a look at the video of the Love Supreme 1965 concert by Coltrane at the Juan les Pins festival. I'm not sure they still have that even if it's supposed to be archived at their place.
No idea who to contact there for a good look at what they have archived. All I know is that they have plenty.
The jazz albums they put out back around 1990 had some incredible concert tapes. They were released on the Esoldun label. Stuff rom Coltrane, Monk, Roland Kirk, Charles Mingus, Stuff Smith, Coleman Hawkins, Count Basie, Woody Herman, Bill Evans among many others. Those CDs disappeared when INA was taken to court by the Monk, Bill Evans, Mingus estates among others. INA was fined a stiff sentence and they have kept away from handling any of those archives.
Doubt they are ready to get back on that field for the time being.