Set Opus Audio Bitrate to 128k in FFmpeg

Setting the audio bitrate for an Opus stream in FFmpeg is a straightforward process that ensures high-quality audio compression. This guide provides the exact FFmpeg command and syntax required to set your Opus audio stream to 128k, along with explanations of the key parameters used and how to control the bitrate mode.

To encode an audio file to the Opus format at 128k, use the following basic FFmpeg command:

ffmpeg -i input.wav -c:a libopus -b:a 128k output.opus

Command Breakdown

• -i input.wav: Specifies the path to your input audio or video file.
• -c:a libopus: Selects the Opus encoder (libopus). This is the standard library used by FFmpeg for Opus encoding.
• -b:a 128k: Sets the target audio bitrate to 128 kbps. You can also write this as 128000.
• output.opus: The name and format of the resulting output file.

Controlling Bitrate Mode (VBR vs. CBR)

By default, the FFmpeg libopus encoder uses Variable Bitrate (VBR) mode. VBR is highly recommended for the Opus codec because it allocates bits dynamically based on the complexity of the audio, offering superior sound quality at 128k.

If your project specifically requires a strict Constant Bitrate (CBR) at 128k, you can disable VBR by adding the -vbr off flag to your command:

ffmpeg -i input.wav -c:a libopus -b:a 128k -vbr off output.opus

If you want to explicitly ensure that standard Variable Bitrate is enabled (which is the default behavior), you can use the -vbr on flag:

ffmpeg -i input.wav -c:a libopus -b:a 128k -vbr on output.opus