Audio issues in MIR evaluation Overview of audio formats Preferred presentation of audio files in an MIR testbed A set of simple recommendations Audio Formats I 1. Apple AIFF (Audio Interchange File Format) 2. Microsoft, IBM WAV (Wave) Stores data in chunks Supports a variety of Bit resolutions Sample rates Channels 2 most common uncompressed formats Digital Audio Workstations support both
Broadcast Wave Format EBU standard Based on Wave audio files Additional header chunk defines data format sound sequence description originator name origination and time Play on any system capable of playing WAV AES31 1. physical data transport How files move between systems via removable media or networks 2. audio file format Broadcast Wave format 3. simple project structure Audio Decision List (ADL) 4. object-oriented project structure
Audio Codecs MPEG-2 MP3 MPEG-4 AAC Advanced Audio Coder, efficient, extensible Dolby Digital AC-3 DTS SDDS (Sony Dynamic Digital Sound) WMA9 High res compression Windows specific features Wrappers and exchange formats AES31 OMF- open media framework, 1997 AAF-advanced authoring format metadata, drm, links, interactive content platform independent, extensible, royalty free MXF- Material exchange format file wrapper read metadata regardless of internal data
Simple Guidelines #1 Audio files should be presented in the highest quality format possible, ideally the original master recordings. If a compressed format is used, it should be used in tandem with the original format. Why? Examples Preparation Companding Equalisation Boost Analysis Wavelet Analysis WMA Time domain analysis low sampling rate files Instrument templates Masking and high frequency content in mp3s
Pre-echo Audio Artefacts Aliasing (low frequency sampling) Birdies (masking) Loss of Stereo Image Repeated Encoding Why use the master recordings? Guarantee highest quality Then test robustness Far richer data 20+ tracks 96kHz + 24 bit Many audio processing methods reverseengineer Source separation Instrument recognition Transcription
Simple Guidelines #2 Audio files should be presented in the most open format possible. Users should be allowed to understand how the file was encoded and access the files from any operating system, on any platform, using any development environment. Simple Guidelines #3 Audio files should be presented in the simplest format possible. Tools should be available to read and write files in that format. Converters should be provided for exchange between all major formats.
Recommendations I Popular, simple, well-understood and uncompressed format for original files WAV Provide various converters Store files in multiple formats Guarantee interoperability and usability OS Development environment Programming language Media player Recommendations II Very low quality popular format with embedded artefacts for listening tests Low sample rate, highly compressed mp3s Mono Watermarks Emphasised responsibility Enhanced liability Thumbnails Streaming Pings, drop-outs,? annoying Listening tests Demonstrations
Do your literature search! Audio restoration services guarantee conversion between any formats recommend broadcast WAV for storage http://audio-restore.com/discussions.html Almost all DAWs support output AIFF and WAV and others AES recommends broadcast WAV