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1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitchesUse FFmpeg’s loudnorm filter with the same loudness, loudness-range, and true-peak targets for every video, but measure each video separately. For a batch of files, a two-pass workflow gives each file its own measurements before processing. The example target values below are practical starting points, not YouTube requirements.
Why normalize each video separately?
Integrated loudness is a better guide to perceived volume than matching sample peaks alone. Two videos can have similar peaks yet sound markedly different in overall loudness. The loudnorm filter targets integrated loudness and true peak, and supports both single-pass and double-pass processing for files. See the FFmpeg Filters Documentation.
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For a YouTube loop made from multiple videos, apply common target settings but use measurements from each individual file. Reusing one video’s measurements across the rest of the playlist undermines the point of per-file normalization.
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Choose targets without treating them as YouTube rules
YouTube’s official upload guidance specifies supported audio formats and sample rate, but the cited guidance does not declare a mandatory LUFS mastering target. Do not treat a particular LUFS figure as a YouTube upload requirement. The values in the commands here—I=-16, LRA=11, and TP=-1.5—are illustrative production choices, not an official platform preset.
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In loudnorm, I is the target integrated loudness in LUFS, LRA is the target loudness range in LU, and TP is the maximum true peak in dBTP. FFmpeg documents ranges of -70 to -5 LUFS for I, 1 to 50 LU for LRA, and -9 to 0 dBTP for TP. Its defaults are I=-24, LRA=7, and TP=-2; defaults are not a YouTube recommendation. Pick targets suited to the material and intended playback, then keep them consistent across the batch.
Normalize each file with a two-pass workflow
1. Measure the input file
Run this once for each video. It analyzes the first audio stream, discards processed output, and prints the measurements needed for the second pass:
ffmpeg -i input.mp4 -map 0:a:0 -af "loudnorm=I=-16:LRA=11:TP=-1.5:print_format=json" -f null -At the end of the output, note that file’s input_i, input_lra, input_tp, and input_thresh values. Keep the measurements associated with the correct input. If a video has no audio stream, this command will fail; omit that video from audio normalization or handle it separately rather than assuming an audio track exists.
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2. Process the file using its own measurements
Replace each uppercase INPUT_* value below with the corresponding measurement from that same file. These are explanatory placeholders, not literal FFmpeg values:
ffmpeg -i input.mp4 -map 0:v? -map 0:a:0
-af "loudnorm=I=-16:LRA=11:TP=-1.5:measured_I=INPUT_I:measured_LRA=INPUT_LRA:measured_TP=INPUT_TP:measured_thresh=INPUT_THRESH:linear=true"
-c:v copy -c:a aac output.mp4This maps the video stream if present and the first audio stream, filters and re-encodes the audio as AAC, and copies the video without re-encoding. -c:v copy does not copy the audio unchanged: the audio must be filtered, so it is encoded again. Check the mapping and codecs against your files and target container; files with multiple audio tracks or unusual stream layouts may need explicit mapping adjustments.
3. Check the filter mode and listen
Linear normalization requires the four measured values. FFmpeg can revert to dynamic mode if linear processing cannot satisfy the requested constraints: the target LRA must not be lower than the source LRA, and the gain must not push true peak above the target. Do not assume the filter will always produce linear-mode output just because linear=true is present. Check FFmpeg’s output and listen to the encoded result, especially at transitions between playlist items.
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Dynamic mode upsamples audio to 192 kHz to detect true peaks, as described in the FFmpeg documentation. If you need a particular output sample rate, set it explicitly with -ar or an aresample filter.
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Automate a batch without mixing up measurements
For a folder of videos, the reliable pattern is to run measurement and processing for each file as a pair. Keep a record keyed by filename, use the same target values for all files, and substitute only that file’s measurements into its processing command. Do not measure one representative file and reuse its values throughout the playlist.
- Run the measurement command for a file and capture its JSON block.
- Associate its four input measurements with that filename.
- Run the processing command for that filename with those values and your shared targets.
- Verify the output exists, has the expected audio and video streams, and plays correctly before adding it to the loop.
Automating JSON extraction can make large batches faster, but ensure the script handles missing audio, unusual stream layouts, and command failures rather than assigning stale measurements to the next file.
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When single-pass normalization makes sense
loudnorm also supports single-pass processing. It can be useful when a separate full-file measurement pass is impractical. It does not provide the same measure-then-process workflow with file-specific measurements gathered from a preliminary analysis of each complete file. For a playlist where consistent treatment across files matters, use two passes when feasible.
For mono input intended for stereo playback, consider whether the dual_mono option is appropriate: FFmpeg documents it as compensation for perceptual measurement differences in that case. Listen to the result on the playback setup that matters to you.
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Prepare the normalized files for YouTube
YouTube’s upload encoding recommendations list AAC-LC, Opus, or Eclipsa Audio and a 48 kHz sample rate. The example encodes audio as AAC but does not explicitly set sample rate; add -ar 48000 if that is the output you intend. YouTube also warns that poor mono compatibility can degrade or mute sound after stereo-to-mono conversion. Check that important content remains audible in mono as well as stereo.
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Normalization during file preparation is distinct from volume processing at playback. YouTube says Stable volume is on by default when watching videos, where available, but it is unavailable for some videos and disabled for YouTube Music and official music videos. See YouTube’s Stable volume help page and its audio enhancements guidance. That playback behavior is not a reason to skip checking the files you prepare.
Troubleshoot common problems
- “Stream specifier” or no audio stream: The input may not contain audio or may use a different stream layout. Inspect the file’s streams and adjust
-map; do not try to normalize a nonexistent audio track. - The filter falls back from linear mode: The source LRA or true-peak constraint may conflict with the requested targets. Confirm that all four measurements belong to the input, review the reported mode, and revise targets if necessary; the filter’s dynamic fallback is not a guarantee of linear processing.
- Output audio is missing or wrong: Review stream mapping and confirm that the selected audio stream is the one you intended. The example deliberately selects the first audio stream with
-map 0:a:0. - Output is unexpectedly large or incompatible: Audio is re-encoded while video is stream-copied. Confirm the output container supports the chosen codecs and select an audio bitrate or codec appropriate to your delivery needs.
- Volume still changes at playlist boundaries: Confirm each file was measured and processed individually with the same targets. Then listen for differences in arrangement, silence, or transitions; loudness normalization does not make different mixes sound identical.
- Audio sounds wrong on some devices: Check the encoded file in stereo and mono, and verify sample rate and channel layout. YouTube notes that poor mono compatibility can cause degraded or muted audio after conversion.
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