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Biamp Systems

Video to Audio Partition Connections

In Tesira, sending signals between partitions is accomplished using Partition Connector blocks. Using Audio Partition Connectors to send audio signals between partitions is relatively straightforward. However, Video Partition Connectors are a bit more flexible, and therefore they are a bit more complicated. Video Partition Connectors don't necessarily only transport video signals; they transport an "AV Stream", which can be a video signal along with multiple audio signals. Video Partition Connectors can send signals between two video partitions, and they can even send signals from a video partition to an audio partition.  The behavior of the Video Partition Connector depends on what types of partitions are being connected.

This article explains the mechanics of Video to Audio (henceforth referred to as V to A) and Audio to Video (A to V) partition connections, along with the considerations required for the transmission of supported audio formats (mono, stereo, 5.1, 7.1). 

Connectors

Video partitions only contain 'Video TX' and 'Video RX' connectors, accessed under 'Speciality Blocks' of the Video Object Toolbar. These connectors serve AV streams to both Video and Audio partitions. Initialization Dialog asks for number of streams. 


 Video_PartitionCon_TX        Video_PartitionConn_RX
Video_PartitionConn_InitDialog

Audio partitions only transmit and receive audio channels. To receive and transmit audio to/from Video partitions, there are special Partition connectors called 'Audio to Video TX' and 'Video to Audio RX'. Initialization dialog asks for the stream format, 'Mono', 'Stereo', '5.1' and '7.1'. These connectors are listed with other types of Partition connectors under 'Specialty Blocks' in the Audio Object Toolbar. 
        AudioToVideo_Block
 VideoToAudio_Init_Dialog

The Video to Audio RX connection dialogs list AV streams (and not audio channels) available for linking in the system. 

Up/Down-mixing audio formats

Since an AV stream may carry audio in any of the four supported formats, this can create a format mismatch when sending audio between Video and Audio partitions.
For example, consider a TesiraLUX IDH-1 connected to Blu-Ray source with embedded PCM 5.1 channel audio. The 5.1 audio stream can be sent to a V to A Receiver block in the Audio partition configured for 2 channels (Stereo) or even 1 channel (Mono). This mismatch of format is handled by either Up mixing or Down mixing audio channels.

In case of the above example, the PCM 5.1 audio (6 channels) will be down-mixed to stereo or mono audio. Since each channel in surround sound may carry different levels of audio, center channel typically being the loudest, the levels are proportionally adjusted:

                                           

Here is an example of Up mixing a Mono source to to 5.1 format:
                                           Upmixing_Mono_5.1.png

The following charts show all the mismatch combinations possible when Up mixing or Down mixing:

                                                                `

 

Note that the signal level for incoming audio from a HDMI/DP digital audio source will show up much louder than what you normally see from analog sources. Gain structure adjustments and processing will be required to manage levels. This can be done with a simple level control, or a more advanced AGC.

DSP usage by Partition Connectors

The V to A and A to V Partition Connectors can be considered as 'Metamixers' for their Upmix or Downmix functionality. To execute this functionality, these connectors require a small amount of DSP processing. Once compiled, the DSP usage will reflect on the blocks (To make DSP usage visible, go to Tools > Options > Application Settings... > Display > Blocks and select 'Display DSP resource requirements).

Configuration shows 1% (.01) DSP usage for A to V Connector and 2% (.02) DSP usage for V to A Connector. This may change based on Audio format selected. 

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