Conversion of MP3 to AAC in the Compressed Domain

In this paper, we propose an efficient algorithm for conversion of an MP3 stream into AAC. Generally, this kind of conversion, transcoding, requires full decoding and re-encoding. However, the re-encoding based transcoding process may result in degradation of quality and take longer than encoding from a PCM signal. This paper proposes a method to inherit the frame structure and quantization scale from MP3 to AAC. This enables a reduction in the iteration process, which requires the most time in the AAC encoding process, without incurring degradation in quality. Experimental results show that the proposed method can perform bitstream domain transcoding at high speed while maintaining a high level of audio quality