Considerations for Recorded Programs
The quality of your audio is critical to the way your program will sound when stations air it. The following provides an overview of basic standards and specifications for programs submitted to the ContentDepot.
Program formats
As the program distributor, you will determine the appropriate format for your program and how it is sent to ContentDepot as well as how it is delivered to stations. Live streams, in addition to being delivered to the ContentDepot in real time over ISDN or other circuits, can also originate as playbacks of pre-recorded media or computer files that you send to the Network Operations Center (NOC—formerly the STC) for playout. Live programs are delivered to stations as streams that stations can send directly to air in real time or record for later playback as permitted by your broadcast rights.
File deliveries of pre-recorded content to stations originate from the ContentDepot as files that you upload via the ContentDepot portal in MP2 audio format. File deliveries can also originate from CDs that you send to NPR Distribution for conversion into MP2 audio files. There is a service charge for us to do this conversion on your behalf (refer to "Costs"). Content for file transfers may also be delivered to the NOC in real time via ISDN or other circuits to be recorded as MP2 files for delivery.
Regardless of the methods chosen for delivery to the stations or to the ContentDepot, it is important that producers adhere to the standards below when producing their content. Failure to observe these standards may result in poor audio quality when the content is played on-air at a station.
NPR Distribution will not be responsible for providing any additional transmissions of programs that do not meet the standards.
Pre-recorded, file-based programs can be automated by stations for broadcast and require the least manual intervention. Therefore, program distributors are encouraged to use the features of the file delivery system whenever possible if this format is appropriate to your program content. Obviously, programming that must be aired in real time (e.g., news and live music events) must continue to be delivered through the system as live streams.
Digital Production Recording Levels
The following are general guidelines for ContentDepot recording levels that must be observed when constructing your program master.
In referencing recording levels, dBfs (decibels or dB relative to full scale) is the scale most often used. This indicates the maximum peak record level as indicated by a metering device such as a digital audio workstation, DAT or CD recorder, or a plug-in metering device. Generally speaking, 0 dBfs is the maximum level. Levels are expressed as negative numbers relative to full scale (fs)-for example, -15 dBfs.
Please note that decibel values have no absolute relationship to the electrical power output of an audio device.
The desired maximum dynamic range between peak and average levels for the ContentDepot is 12 dB. Recommended levels are:
0vu at -15 dBfs
No peaks higher than -3 dBfs
The remaining 3 dB should be left as headroom to allow leeway for future processing and for the inexactness of signal chains.
If you are adding automation cue tones to your program, they should be recorded 5 dB below the selected reference tone level.
- When the reference tone is -15 dBfs, then the cue tone level is -20 dBfs.
Managing program levels is an ongoing discussion of tools and best practices; detailed recommendations are well beyond the scope of this overview. In general, you should produce programs for file delivery with smooth and consistent average levels. Merely keeping peak levels within ContentDepot-recommended limits does not guarantee smooth integration with other programs.