[Libav-user] How to know if lavf guessed the duration from the bitrate or not?

[Michael Bradshaw]

avformat_find_stream_info() attempts to find the file's and streams'
durations, but it will guess them based on the bitrate if it can't
determine the actual duration. This guess can be useful, but I need to
be able to know if the AVFormatContext's or AVStream's duration was a
guess   based on the bitrate or not, so I know how much I should trust
this duration.

Is there a way to know this?

Thanks,

Michael