[FFmpeg-user] Measurement differences between loudnorm and ebur128 filter

[Remko Tronçon]

Hi,

When I run an audio file through the 'loudnorm' filter, I get the following:
    > ffmpeg -i <file> -af loudnorm=print_format=json -f null -
    ...
    "input_i" : "-13.87",
    "input_tp" : "0.06",
    "input_lra" : "8.50",
    "input_thresh" : "-24.45",
    ...

When I run the same audio file through the ebur128 filter, I get the
following:

    > ffmpeg -i <file>  -af ebur128 -f null -
    Integrated loudness:
       I:         -13.8 LUFS
       Threshold: -24.4 LUFS
    Loudness range:
       LRA:         8.7 LU
       Threshold: -34.3 LUFS
       LRA low:   -20.1 LUFS
       LRA high:  -11.4 LUFS

Why are these measurements different? Even if rounding would be towards 0,
that would not explain the LRA difference?

thanks,
Remko