Constrained Variable bit rate is not constraining

[mmynsted]

When using dBpoweramp Music Converter to convert audio files from Flac (also produced by dBpoweramp), the constrained variable bit rate setting is not transcoding the audio file to new file that is constrained to the upper bound defined.

I know this at least two ways. First because an audio player that does not accept files above 256kbps rejects the files and second because I can see the rate in playback, and watch it exceed the defined bounds.

- dBpoweramp Music Converter Release 2025-12-04 (1)
- macOS 26.2 (25C56) on Apple silicon

1. See target is set to `Constrained Variable Bit Rate`
2. Bit Rate is set to 256 kbps








Is there a fix for this?

[PeterP]

I'm sorry but there's no easy fix.

dBpoweramp passes arguments to Apple encoder (afconvert), asking for VBR file with constrained bitrate of 256000 bits per second ( -s 2 -b 256000 ).

It doesn't seem like Apple encoder restricts the bitrate enough for your use case.

To satisfy quirks of specific player, you might have to fall back to constant bit rate, or lower the bitrate enough to mitigate this.

What exact player has such AAC bitrate restrictions if I may ask? Maybe there's some other workaround for this.

[moneymatt4life]

It's an older article, so some things may be as relevant now, but Apple says bitrate selection for cvbr is the lower limit, not an upper limit unfortunately. Unless it's tucked away somewhere in some undocumented -ue property, there isn't a way to select minimum or maximum values like LAME does. While it's possible to be inaccurate in the current operation of the encoder, the note page provides a slightly more in depth description to see if one of the other modes would be more suitable for your needs. Assuming whatever hardware/software issue causing the player to refuse the files can't be worked around to use cvbr that is.