AUDIO Management

AUDIO Management

The way ICE Live manages audio is highly depending on the audio format as well as the type of transport for the signal, as all interfaces do not have the same capabilities for transporting information.

Using a SDI Interface

Traditional SDI audio is uncompressed linear PCM, typically 48 kHz / 24-bit, carried using an AES3-based structure. In HD-SDI, up to 16 audio channels (8 AES pairs) can be embedded in a single SDI signal.

The fixed relationship between audio and the SDI video signal makes SDI a tightly coupled transport: audio channels have a defined position within the signal, rather than being independent network flows. This brings constraints when managing multichannel or Next Generation Audio, particularly around channel allocation, grouping, synchronization, and the limited space available for embedded audio.

For ICE Live, this distinction is important because an SDI signal may contain conventional PCM audio AND / OR NGA-related data, such as MPEG-H or S-ADM, transported using mechanisms defined for non-PCM data over AES3/SDI (SMPTE ST-337).

Audio Layout configuration

SDI transports the audio channels, but does not inherently describe how those channels should be interpreted as an audio layout. For example, a set of 8 or 16 channels could represent different channel layouts or program structures.

Therefore, when using an SDI input, the operator must select the appropriate audio layout so that ICE Live can correctly interpret and analyze the incoming channels.

-> To configure the Audio Layout, In the   Live page, choose AUDIO > CONFIGURATION : Audio Layouts

The way ICE Live output the audio depends on this Audio Layout.
  1. For traditional PCM audio, the output audio will be equivalent to the input audio. In the case of multiple audio layouts (e.g. 2.0 and 5.1), you can select in the AUDIO > CONFIGURATION which one you want to monitor.
  1. For NGA audio, like MPEG-H or S-ADM audio, or mixed with legacy audio,  in addition to the active audio, the operator also needs to select what program, in which rendered configuration (e.g 5.1.4, binaural, etc) and what language he wants to monitor. This is done in AUDIO > PROGRAMS/PRESETS/PRESENTATIONS*
Notes
*ICE Live's interface changes according to the type of NGA selected, and modifies the names of the programs according to each technology: ADM = Audio Programs, Dolby = Presentations, MPEG-H = Presets

Info
This choice of audio layout also affects the audio scopes, as they will automatically reflect the audio layout set


Example for traditional audio


In this example, the second AES pair transports Dolby E (compressed audio using SMPTE ST-337). In this case, to monitor the Dolby E Program 2, the Operator must select:
  1. the audio configuration must be set on 2x 2.0 + 2x5.1 in LIVE > AUDIO > CONFIGURATION
  2. the Program 2 must be selected from the LIVE > AUDIO > PROGRAM tab


Example for MPEG-H audio with Control Track

In an SDI-based MPEG-H production workflow, the audio essence is transported as conventional uncompressed PCM audio, while the MPEG-H metadata is carried separately in a dedicated Control Track. The Control Track is a time-code-like PCM signal containing the metadata required to describe and control the MPEG-H audio scene.
Typically, in a 16-channel SDI configuration:
  • Channels 1–15: PCM audio essence
  • Channel 16: MPEG-H Control Track
  • 48 kHz: same audio clock as the PCM audio
  • Transport: embedded in SDI like a normal audio channel
  • Content: MPEG-H metadata, including information needed to interpret the audio channels/objects, their configuration, labels, positioning, loudness and rendering behavior.
The important point is that the Control Track is not an audio track containing audible content. It is a specially modulated signal that carries the MPEG-H metadata while remaining compatible with the conventional PCM audio infrastructure.
In this example, to monitor the Preset 3, the Operator must select:
  1. the audio configuration must be set on MPEG-H 16ch Control track in LIVE > AUDIO > CONFIGURATION
  2. Select the desired language and audio configuration rendering in LIVE > AUDIO > PRESET
  3. Select the Preset 3 in LIVE > AUDIO > PRESET

Example for S-ADM audio

S-ADM and MPEG-H are NGA, therefore there is no difference for the set up of the audio to monitor. 



In this example, to monitor the Audio Program 3, the Operator must select:
  1. the audio configuration must be set on S-ADM 16ch  in LIVE > AUDIO > CONFIGURATION
  2. Select the desired language and audio configuration rendering in LIVE > AUDIO > AUDIO PROGRAMS
  3. Select the Preset 3 in LIVE > AUDIO > AUDIO PROGRAMS

Example for mixed legacy and S-ADM audio


In this example, to monitor the Dialog Boost presentation, the Operator needs to:

  1. the audio configuration must be set on 2x2.0 + S-ADM 12 ch  in LIVE > AUDIO > CONFIGURATION
  2. Select the desired language and audio configuration rendering in LIVE > AUDIO > PRESENTATIONS
  3. Select the Dialog Boost in LIVE > AUDIO > PRESENTATIONS


Active Audio Soundfield

ICE monitors audio on a soundfield base. Each audio configuration is composed of 1 or more soundfields.
For example:
  1. 16 x mono = 16 soundfields of 1 channel each
  2. 2 x 2.0 = 8 soundfields of stereo
  3. S-ADM 16 channels = 1 soundfield of 16 channels
The audio configuration will then define how ICE Live render the audio (audio output) but also how the audio scopes will measure the audio.

The video scopes measure and analyse the ACTIVE SOUNDFIELD only.

In the case of multiple soundfields , by default the active soundfield is the first one.

-> To change the active soundfield, use the keyboards 1 and 2 key to go to next or previous soundfield.


Automatic audio detection

Even though using the SDI as transport, with no metadata present to carry the audio layout information, ICE Live is able to detect some specific audio patterns and deduct the current audio format for some cases.

Dolby E detection

Notes
The  actual decoding of Dolby E requires a specific Dolby decoding licence. However,  even without this license, ICE live can display the Dolby E metadata (programs, audio configurations, etc) and allows the validation of the signal, but will not decode the audio.

In order for ICE Live to detect the Dolby E, and because the Dolby E is only carried in a stereo pair, the Audio Layout must be set on audio pairs.

In the exemple below, the Audio Layout is set on 16 x mono.


We can easily identify visually on the VU meter the location of the Dolby E on channels 5 to 8, and can deduct that the suitable audio configuration, here 2 pairs of normal stereo and 2 pairs of Dolby E audio.

When we set the Audio Layout is set on 8 X 2.0, the VU meter starts to show a relevant audio:


-> In order to display the Dolby E program informations, use keyboard 1 or 2 to select the desired active soundfield (here the 3rd and 4th ones)

-> The program information is displayed in the  AUDIO > PROGRAM tab

S-ADM detection in a mixed audio configuration

ICE Live is always looking if ADM metadata are present in the last channel of a particular soundfield. In the exemple described on the diagram above using the France TV mixed audio use case, and even if the audio configuration is not set properly, for example on S-ADM 16 channels, ICE Live detects the ADM metadata in the last channel, and using the metadata present in the XML is able to output the chosen program accordingly.