Compared to previous peak-based or speech-based attempts of controlling level in broadcast, the BS.1770-2 standard is a remarkable improvement. As shown in Figure 1, even if only digital television (like ATSC A/85) is considered, and mobile TV, podcast and analog distribution are disregarded, the new standard is a giant step forward for audio quality. A fully transparent loop, based entirely on open technology, may now be created between production, ingest, transmission and the home listener, as shown in Figure 2.
Consequently, “sausage processing” at the point of transmission should be considered a thing of the past. Instead, BS.1770-2-compliant metering in production, and at subsequent stages, allows transparent handling and normalization of audio in the chain.
For broadcast platforms based on AC3, the BS.1770-2 measurement also enables a more precise and cheaper setting of dialnorm metadata than ever before. Remember, AC3 decoders are not dialogue-specific, neither with regard to normalization (dialnorm), nor with regard to processing (DRC).
For the plethora of other platforms — mobile TV, IPTV, podcast and counting — BS.1770-2 provides easy and audio-conscious answers also, especially in combination with complementary measurements such as momentary loudness, short-term loudness and loudness range.
Under the new order, programs remain untouched, as long as their loudness range isn’t excessive for the audience of a given platform. This is also an improvement over today, because AC3 processing (DRC) is typically routinely enabled during DTV transmission. Where this kind of domestic processing was supposed to be non-destructive, DRC has ironically become anything but: The home listener cannot turn off a primitive processor that is not even BS.1770-compliant.
In an ideal world, no matter what the program type, the perceived loudness level would stay about the same throughout a full day of broadcast, across channels, across platforms. We’re close to that goal, and it all starts with the BS.1770-2 standard. Further complementary tools should not be dismissed, but the good news is that progress is being made constantly as users everywhere gain experience with the audio revolution that is taking place before our ears. The mere fact that broadcasters, as well as legislative assemblies, across the globe are now focusing on loudness solutions is a positive and welcome development that is sure to make the viewing — and, not least, listening — experience more enjoyable for everyone.
—Thomas Lund is the HD development manager at TC Electronic.