Subjective Evaluation of Music Compressed with the ACER Codec Compared to AAC, MP3, and Uncompressed PCM

Abstract

Audio data compression has revolutionised the way in which the music industry and musicians sell and distribute their products. Our previous research presented a novel codec named ACER (Audio Compression Exploiting Repetition), which achieves data reduction by exploiting irrelevancy and redundancy in musical structure whilst generally maintaining acceptable levels of noise and distortion in objective evaluations. However, previous work did not evaluate ACER using subjective listening tests, leaving a gap to demonstrate its applicability under human audio perception tests. In this paper, we present a double-blind listening test that was conducted with a range of listeners (N=100). The aim was to determine the efficacy of the ACER codec, in terms of perceptible noise and spatial distortion artefacts, against de facto standards for audio data compression and an uncompressed reference. Results show that participants reported no perceived differences between the uncompressed, MP3, AAC, ACER high quality, and ACER medium quality compressed audio in terms of noise and distortions but that the ACER low quality format was perceived as being of lower quality. However, in terms of participants’ perceptions of the stereo field, all formats under test performed as well as each other, with no statistically significant differences. A qualitative, thematic analysis of listeners’ feedback revealed that the noise artefacts that produced the ACER technique are different from those of comparator codecs, reflecting its novel approach. Results show that the quality of contemporary audio compression systems has reached a stage where their performance is perceived to be as good as uncompressed audio. The ACER format is able to compete as an alternative, with results showing a preference for the ACER medium quality versions over WAV, MP3, and AAC. The ACER process itself is viable on its own or in conjunction with techniques such as MP3 and AAC.

Effectiveness of MP3 Coding Depends on the Music Genre: Evaluation Using Semantic Differential Scales

“…In order to form the questionnaire for this study, various other approaches and questionnaires from other audio-linked studies were taken into account [24,25,[38][39][40][41][42]. For this study, the semantic differential method [27] was selected in order to evaluate various aspects of the MP3 compression effects.…”

“…According to [18,19], the most common artifacts are the birdie effect, pre-echo effect, spectral clipping in the high frequencies, spatial distortions and temporal smearing. Most of the previous work carried out focuses on the objective evaluation of the MP3 algorithm [20][21][22], the comparison of the algorithm with high resolution audio [23] and the comparison among different compression algorithms (in terms of quality) for a variety of music genres [24], rather than the comparison between the MP3 and WAV formats [25,26]. Although these studies have identified and described in detail the nature of the MP3 artifacts and the impact these have on the audio signal, the human factor is almost absent in the majority of them.…”

Evaluating Use of the Doppler Effect to Enhance Auditory Alerts

“…It was anticipated that additional, descriptive information about the qualities of the sounds might be highlighted using timbral descriptions, as well as the five-point scale antonyms, as well as reflection upon the sounds and the testing process itself. Thematic analysis and qualitative techniques are found to provide useful insight in audio listening studies (Francombe et al, 2018;Ratcliffe, Gatersleben, & Sowden, 2013) and can be used to complement and triangulate with quantitative data (Cunningham & McGregor, 2019).…”