Unlike traditional hardware solutions, like DP 600, the AudioTools WFC option, with its rich XML language created specifically to define complex audio processing, provides an infinite number of possible Workflows. Though our technical services staff is experienced in creating custom Workflows for each of our customer’s specific needs, here are some examples of typical use cases, with pictorial representations of how each works.
Sequential Loudness Control
This basic Workflow is typical of a simple Job that begins with multichannel plus stereo MXF audio essence and ends with loudness corrected audio ReWrapped back into the original container…The process begins with essence extraction of the two separate programs, stereo and surround, from an MXF wrapper. Once the audio data is available, it can be measured for EBU and/or ITU Programme Loudness, Maximum True Peak Level, Loudness Range, Maximum Momentary and/or Short Term Loudness. For dialog-centric content, Dialog Intelligence can be used. Otherwise, the standard ITU 1770-2 gated loudness metric is employed. Once loudness values are obtained, the Program Loudness is adjusted according to the measured value, and True Peak Limiting is applied to ensure it’s in compliance. Then, the 5.1 + 2 essence is re-inserted into the wrapper.
Sequential Dolby E Downmix
This basic Workflow is another typical example that runs as a simple Job through AudioTools Server. It begins with extraction of Dolby E-encoded multichannel essence. The Dolby E data is decoded, and the 5.1 audio is downmixed to a stereo Left total/Right total or LtRt pair. The originally extracted 5.1 mix plus the new LtRt are encoded into a new Dolby E file, maintaining all relevant metadata extracted during the decode operation, and inserted back into the original MXF container.
Complete Loudness Control
In contrast to the linear Workflow shown above for simple loudness control, the inclusion of AudioTools WFC allows AudioTools Server to provide complex, comprehensive processing. This could include loudness measurement and correction as well as many other processes, including upmix/downmix, quality control, encoding/decoding/transcoding and sample rate/time domain modification.
The Workflow below begins with wrapped, mixed-format audio essence. Four programs are extracted, with Dolby E decoding occurring on programs 3 and 4 which results in multiple additional stereo and surround programs being generated. Once all programs are in linear PCM format, they are handed to the loudness measurement module. This is the first instance of conditional Workflow control coming into play as the results of measurement prior to adjustment as well as measurement after adjustment being weighed by AudioTools WFC to determine if the Loudness targets have been met. If the target is hit, then no further adjustment is made. If not, the adjustment is performed with appropriately altered values to hit the targets. At every step in the process, AudioTools Server’s prime directive is to determine if processing is needed at all.
There are certain types of program material that require iterative Loudness Range passes due to the nature of the R 128 Loudness Range specification. AudioTools WFC transparently handles iterative processing with user definable timeouts, which handles exceptional examples of irregular audio. Workflows allow you to customize the action taken on timeout, such as pausing and waiting for manual intervention before restarting the Workflow.
Once all the audio is in compliance, programs 3 and 4 are re-encoded, and the dialnorm metadata values are updated using the findings of the final measurement step after True Peak Limiting. All of the essence is now ready for ReWrapping back into the original QuickTime or MXF container.
An Integrated Workflow Example
The example below shows how the flexibility of AudioTools Server’s processing, driven by AudioTools WFC, can deliver unattended quality control and delivery of mastered assets around the clock. This real world example starts with a variety of wrapped assets and individual audio files. The wrapped programs are extracted, analyzed, and decoded as required. The resulting material is verified to determine if the two independent stereo PCM and 5.1 PCM programs are, in fact, derived from the 5.1 Dolby E-decoded content. If the wrong mix was inserted in the source, AudioTools Server diverts the asset to an ERROR container for manual intervention. If the Program Correlation test is passed, the content passes on to channel order verification where the channel configuration is checked against the expected configuration, and verified or rejected.
Once the channel configuration is known, the decoded 5.1 material is downmixed to an LtRt stereo version. That content, along with a surround M&E element and multilingual stereo dialog elements, are re-encoded as separate Dolby E files. In the ReWrap and Assemble phase, all the elements, some unaltered and brought in directly from the original sources and some created on-the-fly by AudioTools Server, are slotted into a final master container. Additionally, if a downstream participant requires the addition of placeholders, AudioTools Server can insert silent channels into the final master. All this is possible with little or no human intervention, running unattended 24/7.
AudioTools Server is the de facto standard in the EU for automated file-based loudness control and QC. Some of our happy AudioTools customers who have addressed their automated audio processing workflows include: