An AXI4-Stream audio cycle is illustrated in the following figure. The data is valid when both the valid (TVLD) and ready (TRDY) signals are asserted. The HDMI 2.1 RX Subsystem sends out adjacent channels in sequential order (CH0, CH1, etc.). Usually, the audio stream receiver also expects the channels in sequential order. If the channel data is not in order, the channel data might be mapped into other channel sample slots. Audio signals are defined in Audio Output Stream Interface.
In the HDMI 2.1 RX Subsystem the audio information, such as format and number of channels, are extracted from the video stream. This information is available through API calls.
- XV_HdmiRxSs1_GetAudioFormat
- XV_HdmiRxSs1_GetAudioChannels
The actual audio data is extracted and sent to AUDIO_OUT interface. Similarly, the ACR values are extracted from the ACR packets and sent to ACR ports.
If an HDMI system does not require audio, tie all audio related input ports Low. The ports are:
- s_axis_audio_aresetn
- s_axis_audio_aclk
- AUDIO_OUT_tready
Audio related output can be left unconnected. The ports are:
- AUDIO_OUT (except tready)
- acr_cts
- acr_n
- acr_valid
In the HDMI 2.1 RX Subsystem, L-PCM (IEC 60958, Packet Type 0x02), HBR (Packet Type 0x09), and 3D Audio (Packet Type 0x0B) are handled by the hardware. For Aux packet with packet type = 0x02, the audio data are routed to the audio interface. Therefore, even IEC 61937 compressed audio is available at the audio interface. In this case, you must develop your module to retrieve and uncompress the audio.