Normalize audio volume using ffmpeg's two-pass loudnorm filter.

Process

•Analyze audio to measure current loudness levels
•Normalize using measured values for accurate results
•Output with suffix _normalized in same format (or user-specified format)
•Display before/after summary

Step 1: Analyze Audio

Run the analysis pass to measure loudness:

bash

ffmpeg -i "<input-file>" -af "loudnorm=I=-16:LRA=11:TP=-1.5:print_format=summary" -f null -

Parse the output for these values:

•Input Integrated → measured_I (e.g., -22.6)
•Input True Peak → measured_TP (e.g., -2.6)
•Input LRA → measured_LRA (e.g., 19.8)
•Input Threshold → measured_thresh (e.g., -35.1)

Step 2: Normalize Audio

Run the normalization pass with measured values. Choose encoder based on output format:

Format	Encoder flags
mp3	`-c:a libmp3lame -q:a 2`
m4a	`-c:a aac -b:a 192k`
flac	`-c:a flac`
wav	`-c:a pcm_s16le`
ogg	`-c:a libvorbis -q:a 6`

bash

ffmpeg -i "<input-file>" -af "loudnorm=I=-16:LRA=11:TP=-1.5:measured_I=<measured_I>:measured_LRA=<measured_LRA>:measured_TP=<measured_TP>:measured_thresh=<measured_thresh>" <encoder-flags> "<output-file>"

Output file: Same directory, base name with _normalized suffix, same extension as input (e.g., audio.m4a → audio_normalized.m4a).

Step 3: Display Summary

Present a before/after comparison:

code

## Audio Normalization Summary

| Metric           | Before     | Target     |
|------------------|------------|------------|
| Integrated       | -22.6 LUFS | -16.0 LUFS |
| True Peak        | -2.6 dBTP  | -1.5 dBTP  |
| Loudness Range   | 19.8 LU    | 11.0 LU    |

Output: /path/to/audio_normalized.m4a

Target Levels

Default targets optimized for podcasts/YouTube/general streaming:

•Integrated loudness: -16 LUFS
•True peak: -1.5 dBTP (headroom for lossy encoding)
•Loudness range: 11 LU

Other platform standards for reference: Spotify/YouTube (-14 LUFS), broadcast EBU R128 (-23 LUFS).