Loudnorm filter returns positive input_i

[derkades]

To use the loudnorm filter in 2-pass mode measured_I, among other values, needs to be set. This is a value between -99 and 0, according to the documentation. I believe measured_I should be set to the input_i value returned by the measurement pass. However, for one specific mp3 file, I found this value to be greater than 0.

Measurement pass command:

ffmpeg -hide_banner -i "Don't look back.mp3" -map '0:a' -af loudnorm=print_format=json -f null -

Output:

[Parsed_loudnorm_0 @ 0x7490e00] 
{
        "input_i" : "26.43",
        "input_tp" : "76.06",
        "input_lra" : "40.70",
        "input_thresh" : "-9.44",
        "output_i" : "-23.17",
        "output_tp" : "-2.00",
        "output_lra" : "6.20",
        "output_thresh" : "-33.22",
        "normalization_type" : "dynamic",
        "target_offset" : "-0.83"
}

When passed to the filter again, this causes an out of range error:

[loudnorm @ 0x564632fbe900] Value 26.430000 for parameter 'measured_I' out of range [-99 - 0]
[loudnorm @ 0x564632fbe900] Error setting option measured_I to value 26.43.
[Parsed_loudnorm_0 @ 0x564632fba400] Error applying options to the filter.
[AVFilterGraph @ 0x564632fad900] Error initializing filter 'loudnorm' with args 'I=-16:TP=-1.5:LRA=11:measured_I=26.43:measured_TP=76.06:measured_LRA=40.70:measured_thresh=-9.44:offset=-0.83:linear=true'
Error reinitializing filters!
Failed to inject frame into filter network: Numerical result out of range
Error while processing the decoded data for stream #0:0
Conversion failed!

Using ffmpeg git master 2023-10-06 build from johnvansickle.com

[derkades]

I have uploaded the file in question to streams.videolan.org, with the name "loudnorm_filter_positive_loudness.mp3".

[Elon Musk]

Either file is too short, or have out of range values -1/1.