Especially when dealing with older material it is common practice to restore the audio-visual content in order to create a sharper sound and image. Material from olden days often suffered from external influences and therefore deteriorated rapidly. Moreover, the recording technologies used back then were slightly less sophisticated.
In restoring damaged sound recordings we try to minimize unwanted noise as much as possible in order to restore the highest level of audibility. We filter out all noticeable artefacts like cracking, static and other interfering background noises.
Restoring video footage includes colour restoration, polishing away blots and spots (a well-known problem with older films) and unwanted noise reduction.
When the restoration is complete adding metadata is the next important step to ensure that the new material can be archived for use at a later date.