ABSTRACT
Recording delays an audio signal. For a radio interview the delay might involve only a few seconds, just enough for a ‘top and tail’ edit. On the other hand, a transcription recording of a live concert could well be recorded and then lay dormant for a century or more. Nowadays, economic pressures in the broadcast industry
demand a recording process that is far more complex than these two examples represent. For instance, if a recording can be made available to multiple operators soon after the start of that recording, the editing processes for different distribution paths and different programmes could take place in parallel. Therefore, we now need to think of broadcast sound record-
ing as a part of general ‘workflow’, and in this context the audio will in all probability accompany other ‘essence’ such as text and pictures. These essence items are all linked together by the ‘metadata’, which takes the place of the information once carried on the label and package of a disc or tape recording, although the metadata by itself possesses a much greater potential power than a label. For the overall workflow process to be a success, there are
several presumptions that are made about the sound recording. Firstly, the technical quality of the recording must be adequate to survive the numerous signal processing and editing procedures that may be applied at any stage along the workflow route. Another way of putting this requirement is to demand the ‘transparency’ of the recording stage, meaning that the other items in the signal chain produce greater level of impairments than the recording. This does not mean that current sound recording practices are perfect, it simply means that the recording should be better than the worst other items in current use in the audio signal chain. This requirement leaves implications about any bit rate reduction of the recording. The highest source quality should be preserved as far along the workflow chain as possible. This then preserves the possibilities for later processing, or for future (and possibly lucrative) applications of the recorded material. The
days of needing bit-rate-reduced recordings for the convenience or economic use of Information Technology (IT) applications are long over, although low-bit-rate contribution of interviews, and similar recordings over dial-up telephone circuits, is likely to remain a prime use of bit rate reduction for many years to come. This should not give the impression that sterility has crept into
sound recording. In reality, the creative opportunities available in the most basic computer recording equipment well exceed those existing in the most complex analogue studio facilities of 10 years ago. What has gone are the subtle perceptual sound effects that were inherent in analogue recording or noise reduction processes. However much of a cult built up around some of those effects over the years, there can be no doubt about the technical efficiency of a digital recording process. Digital recording has enabled big and helpful changes in audio production, mainly as a result of the ‘transparency’ factor. For instance, the recording of two-channel stereo in the form of Mixed and Side (M and S) channels was not considered using analogue equipment, because any recording artefacts such as noise on the M channel would appear as a coherent centre image in the reproduced sound field. ‘A and B’ (Left and Right channel) analogue recording resulted in a much more diffusely reproduced field of any recording noise; therefore, this method became the standard for two-channel stereo recording. Now M and S recording can prove very useful, and there are other examples of such potential useful recording techniques being discovered (or rediscovered) as the freedoms of digital recording become apparent. Perhaps this is a good point to step back from the actual
details of the recording technology, and ask if we have actually experienced some kind of Digital Audio Revolution.
