Incorrect FPS when creating webm dash files

[Aleksandar Milovanovic]

Summary of the bug:

I am trying to transcode from image sequence to webm dash streaming files. I can do that successfully, but ffprobe shows invalid FPS for those afterwards (in this example, 30.30 instead of 30). If I just copy codec into new webm file from dash, it still provides invalid FPS info.

Everything mentioned does not happen for mp4 dash streaming files (they have correct FPS all the time).

Note that manifest.mpd has a property inside stating frameRate="30/1", but that is ignored by the ffprobe.

How to reproduce:

# ffmpeg version is 6.0-essentials_build, but it is the same with 5.1, and I guess others (don't think this is a regression)
# I will attach a very small repro of just 3 jpg files that can be used to reproduce the issue

# Create webm dash manifest in question, with 30 fps input creates files that are described with 30.30 fps
ffmpeg -y -framerate 30 -i "img_%2d.jpg" -c:v libvpx-vp9 -f dash -dash_segment_type webm manifest.mpd
ffprobe manifest.mpd

# Even after moving to webm container (without reencoding), fps is still 30.30
ffmpeg -y -c:v libvpx-vp9 -i manifest.mpd -c copy out.webm
ffprobe out.webm

[Aleksandar Milovanovic]

minimal repro described in the ticket