Solved: Traktor "ID3-Tags could not be read" caused by corrupted M4A containers, not corrupted audio

SWee13

Traktor repeatedly displayed the message "WARNING: ID3-Tags could not be read for ..." during startup. Some tracks were also repeatedly analysed, and metadata changes such as BPM, beatgrids and cue points were not always written back reliably. My theory is that a playlist or cleanup tool modified these M4A containers at some point in the past. The affected files played perfectly in Apple Music and showed no obvious corruption.

The relevant log file on macOS is:~/Documents/Native Instruments/Traktor <version>/Logs/Traktor.log

The log contained entries pointing to the affected M4A files.

The root cause was not damaged AAC audio. The issue was the M4A container itself. Apple Music could read the files without problems, while Traktor had difficulties reading and writing metadata.

I rebuilt the M4A containers with a lossless FFmpeg remux using stream copy only. No audio was re-encoded; Apple Music continued to play the files normally; Traktor stopped reporting ID3 errors; and BPM, beatgrids, and cue points remained intact after restarting Traktor.

One additional finding may help others: Traktor escapes certain characters in its log files, including brackets and underscores. If you automatically extract affected file paths from the log, you must remove those escape characters, or some files may be missed.

Hopefully, this helps others who are seeing this error and assume the audio files themselves are damaged. In my case, the audio was fine. The container was the problem.

SWee13

For anyone who wants to reproduce the process, these were the exact steps I used.
If not already available, install ffmpeg from Martin-Riedl. Below is my Terminal script, be sure

Step 1: Close Traktor, Apple Music and any tagging software.

Step 2: Extract the affected file paths from Traktor.log.

Paste the following command into Terminal:

LOG="$HOME/Documents/Native Instruments/Traktor 3.11.1/Logs/Traktor.log"
LIST="$HOME/Desktop/traktor-affected-m4a.txt"
MISSING="$HOME/Desktop/traktor-unresolved-paths.txt"

: > "$LIST"
: > "$MISSING"

grep 'ID3-Tags could not be read for ' "$LOG" |
sed -E 's/^.*ID3-Tags could not be read for //; s/.$//' |
sed 's/\[/[/g; s/\]/]/g; s/\//g; s/\\/\/g' |
sort -u |
while IFS= read -r file
do
if [ -f "$file" ]; then
printf '%s\n' "$file" >> "$LIST"
else
printf '%s\n' "$file" >> "$MISSING"
fi
done

Step 3: Check how many affected files were found.

echo "Found: $(wc -l < "$LIST")"
echo "Missing: $(wc -l < "$MISSING")"

Step 4: Create the repair script.

Run:

nano ~/Desktop/remux_traktor_files.sh

Paste the following script into Nano:

#!/bin/bash

set -u

ROOT="$HOME/Music/Music/Media.localized/"
LIST="$HOME/Desktop/traktor-affected-m4a.txt"
LOGDIR="$HOME/Desktop/traktor-remux-logs"

DONE="$LOGDIR/success.txt"
FAILED="$LOGDIR/failed.txt"
MISSING="$LOGDIR/missing.txt"

mkdir -p "$LOGDIR"
touch "$DONE" "$FAILED" "$MISSING"

command -v ffmpeg >/dev/null 2>&1 || exit 1
command -v ffprobe >/dev/null 2>&1 || exit 1

while IFS= read -r file || [ -n "$file" ]
do
[ -z "$file" ] && continue

if grep -Fqx "$file" "$DONE"; then
    continue
fi

[ -f "$file" ] || continue

dir=$(dirname "$file")
base=$(basename "$file")
stem="${base%.*}"

tmp="$dir/.${stem}.remux-temp.m4a"

rm -f "$tmp"

if ffmpeg -nostdin -v error -y \
    -i "$file" \
    -map 0 \
    -map_metadata 0 \
    -c copy \
    "$tmp"
then
    codec=$(ffprobe -v error \
        -select_streams a:0 \
        -show_entries stream=codec_name \
        -of default=noprint_wrappers=1:nokey=1 \
        "$tmp" 2>/dev/null)

    if [ -n "$codec" ]; then
        touch -r "$file" "$tmp"
        mv -f "$tmp" "$file"
        printf '%s\n' "$file" >> "$DONE"
    else
        rm -f "$tmp"
        printf '%s\n' "$file" >> "$FAILED"
    fi
fi

done < "$LIST"

Save with Ctrl+O, press Enter, then exit Nano with Ctrl+X.

Step 5: Make the script executable.

chmod +x ~/Desktop/remux_traktor_files.sh

Step 6: Run the script.

~/Desktop/remux_traktor_files.sh

Step 7: Start Traktor again and verify the result.

Clear the log first:

: > "$HOME/Documents/Native Instruments/Traktor 3.11.1/Logs/Traktor.log"

Start Traktor, wait until the collection has loaded, close Traktor and check the log:

LOG="$HOME/Documents/Native Instruments/Traktor 3.11.1/Logs/Traktor.log"

echo "Unreadable: $(grep -c 'ID3-Tags could not be read' "$LOG")"