Assessing the quality of audio and video media files and identifying defects in digitized content of the Montreux Jazz Festival archive.
Quality assessment for digitized content from analogue magnetic tapes (2/3 of the MJF archive) was completed in December 2014 and a description is provided below. From January 2015, quality asessment is continuing as part of the HD Capture process to the remaining audio-visual content (1/3 of the MJF archive).
Quality Assessment began at EPFL in 2011 a few months after the first batch of inventoried tapes from the Montreux Jazz Festival archive was sent to Vectracom for large-scale digitization. The Quality Assessment procedure aims to ensure digitization of original source media was performed according to a set of standards defined by specialists at EPFL. Two workstations were used by an AV technician and students to complete routine checks on all digitized concerts supplied to EPFL by Vectracom.
Audio and video quality assessment criteria:
- Audio level (maximum and average peak level, maximum RMS)
- Audio defects (cuts, saturation, crackling, balance bias, hum, hiss, pops, tones etc.)
- Audio phase correlation, audio balance, spectral analysis
- Video level (maximum and minimum chrominance and luminance)
- Video defects (cuts, dropouts, lines, jumps, color, stroboscopic effect etc.)
- Overall auido-visual quality grade (ok/not ok)
Once identified, the nature and location in the time-code of a concert for a particular defect is recorded in the Montreux Jazz Digital Project database. This information is of great value for research purposes. These data entries can serve as a reference for algorithms and automated control processes.
Origins of audio and video defects:
- Recording equipment
- Original source tape
- Playback equipment
- Digitization process
If a defect is due to the digitization process or tape reader, re-encoding may be necessary. If a defect is native to the original tape or due to original recording techniques, solutions can be developed by labs at EPFL to adjust and repair the problem such as the video defect detection and correction tool developed by MMSPG lab.
Quality Assessment workstation equipment:
- Adobe Premiere CS6
- Adobe Audition CS6
- Pro Tools
- Black magic design professional image and audio analysis tool
- JVC high performance monitor for image observation and analysis
- AJA digital video interface
- High quality headphones and loudspeakers