[FFmpeg-devel] [PATCH v2] doc/filters: Add double-pass example for loudnorm

[Carl Eugen Hoyos]

2018-08-20 7:30 GMT+02:00, Gyan Doshi <gyandoshi at gmail.com>:
> On 20-08-2018 03:27 AM, Marvin Scholz wrote:
>
>> + at example
>> +$ ffmpeg -i input -map 0:a -af loudnorm=I=-23:TP=-1:print_format=summary
>> -f null -
>> +
>> +[...]
>> +Input Integrated:     -9.0 LUFS
>> +Input True Peak:      +1.5 dBTP
>> +Input LRA:             9.4 LU
>> +Input Threshold:     -19.5 LUFS
>> + at end example
>> +
>> +Then pass the input measurements to the next run that produces the
>> result:
>> +
>> + at example
>> +ffmpeg -i input -af
>> loudnorm=I=-23:TP=-1:measured_I=-9.0:measured_TP=1.5:
>> measured_LRA=9.4:measured_thresh=-19.5:print_format=summary
>> output
>
> a) Your first pass command will run the filter for all audio streams in
> the input, but your 2nd pass command won't. Suggest you remove the mapping.

Or use -map 0:a:0

Carl Eugen