An audio processing device includes an initial processing module to generate a stream of frequency coefficients based on input audio data, a watermarking module to embed a digital watermark into the stream of frequency coefficients to generate a modified stream of frequency coefficients, and a final processing module to process the modified stream of frequency coefficients to generate output audio data. In some implementations, the input audio data comprises unencoded audio data, the initial processing module comprises a frequency domain transform module to perform a time-to-frequency domain transform to generate the unencoded audio data, and the output audio data is encoded audio data. In other instances, the input audio data comprises encoded audio data, the initial processing module comprises an initial decoding module to partially decode the encoded audio data to generate the stream of frequency coefficients, and the output audio data is decoded audio data.