descriptor formatDataRate expresses the amount
of data in a digital media file that is encoded, delivered or distributed, for every
second of time. Although optimal data rates are often dependent
on the codec used to compress and encode a digital file, generally
speaking, a larger data rate translates into a better quality playback experience, for example 56 kilobits/second vs. 1 megabit/second. Different components of an asset may have their own data rates and when combined report a total data rate. This metadata element can accommodate any of these specifications.
The measurement scale applied to a data rate is variable
depending on the intended purpose of the file (editing, distribution
over LAN or Internet, etc.) The measurment scale may also be dictated by a particular DAM, CMS, or playout storage system. Enter a number followed by the measurement
Data rates for a digital file can refer to...
- video data rate
- audio data rate
- combined total data rate
When entering data rate information, determine which data rate information is needed for your indexing purposes and by your users. Total data rate expresses the complete data transfer load for a file and is likely the most useful. If cataloging the separate data rates for video and/or audio tracks is of importance, then either or both of these should be indicated.
The pbcoreInstantiation container should not be repeated in order to express a video data rate and an associated audio data rate. The two combined are part of a single instantiation for an asset. If, however, a separate audio file is derived from the asset (such as a standalone mp3 file), it is considered a separate rendition of that asset and worthy of a repeated instantiation set of metadata.
PBCore suggests you indicate which data rate you are reporting. For example..
- Video 1930 kilobits/sec
- Audio 230 kilobits/sec
- Total 1930 kilobits/sec; Video 1700 kilobits/sec; Audio 230 kilobits/sec