[FFmpeg-user] FFmpeg AAC encoder produces harsh noise on specific voice

[Ferdi Scholten]

On 09-08-2025 11:25, Agent 45 wrote:
> Hello, FFmpeg team,
>
> I'm encountering a consistent issue when encoding voice with FFmpeg AAC
> encoder.
> At low and medium bitrates the encoded output contains noticeable and
> sometimes harsh noise when encoding specific vocals.
> These noise gradually reduce as the bitrate increases.
>
> I’ve attached all files (input and encoded outputs).
> Here are the commands used, ffmpeg version 7.1.1:
>
> ffmpeg -i input1.wav -c:a aac -b:a 128k output1_128k.m4a
> ffmpeg -i input2.wav -c:a aac -b:a 128k output2_128k.m4a
> ffmpeg -i input3.wav -c:a aac -b:a 128k output3_128k.m4a
>
> ffmpeg -i input1.wav -c:a aac -b:a 192k output1_192k.m4a
> ffmpeg -i input2.wav -c:a aac -b:a 192k output2_192k.m4a
> ffmpeg -i input3.wav -c:a aac -b:a 192k output3_192k.m4a
>
> ffmpeg -i input1.wav -c:a aac -b:a 256k output1_256k.m4a
> ffmpeg -i input2.wav -c:a aac -b:a 256k output2_256k.m4a
> ffmpeg -i input3.wav -c:a aac -b:a 256k output3_256k.m4a
>
> # Observations:
>
> - All 128k versions contain harsh noise, and almost the same if increase
> the bitrate to 160k
>
> - `output1_192k.m4a`: noise at around 0.27s
> - `output2_192k.m4a`: No obvious noise detected
> - `output3_192k.m4a`: Mild noise at around 0.05s and some noise still
> present from 0.3s
>
> - `output1_256k.m4a`: noise at around 0.27s
> - `output2_256k.m4a`: No obvious noise detected
> - `output3_256k.m4a`: Mild noise around at around 0.05s
>
> - No noise detected when increased to 320k
>
>
Please supply the full ffmpeg command as there are several ways and 
encoders to generate AAC with ffmpeg.

For best quality, use the libfdk-aac encoder