This is the fundamental unit of time (in seconds) in terms
of which frame timestamps are represented.
decoding: set by libavformat
encoding: May be set by the caller before avformat_write_header() to
provide a hint to the muxer about the desired timebase. In
avformat_write_header(), the muxer will overwrite this field
with the timebase that will actually be used for the timestamps
written into the file (which may or may not be related to the
user-provided one, depending on the format).
This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented.
decoding: set by libavformat encoding: May be set by the caller before avformat_write_header() to provide a hint to the muxer about the desired timebase. In avformat_write_header(), the muxer will overwrite this field with the timebase that will actually be used for the timestamps written into the file (which may or may not be related to the user-provided one, depending on the format).