For HDMI, all data island packets consist of a 4-byte packet header and a 32 bytes of packet contents. The packet header, represented in the following figure, contains 24 data bits (3 bytes) and 8 bits (1 byte) of BCH ECC parity.
The packet body, represented in the following figure, is made from four subpackets; each subpacket includes 56 bits (7 bytes) of data and 8 bits (1 byte) of BCH ECC parity.
- ECC is calculated in the HDMI 2.1 TX Subsystem. Therefore, you must construct HB0...HB2, and PB0, PB1...PB26, PB27 according to HDMI specs in the software.
- When calculating the checksum value (PB0), the ECC values are ignored.
- Refer to section 5.2.3.4 and 5.2.3.5 of the HDMI 1.4 specification (https://www.hdmi.org/spec/index) for more information on the Aux packet structure.
In the following table, the packet types are identified as handled by hardware and handled by software.
| Packet Type Value | Packet Type |
|---|---|
| 0x00 1 | Null |
| 0x01 1 | Audio Clock Regeneration (N/CTS) |
| 0x02 1 | Audio Sample (L-PCM and IEC 61937 compressed formats) |
| 0x03 1 | General Control |
| 0x04 | ACP Packet |
| 0x05 | ISRC1 Packet |
| 0x06 | ISRC2 Packet |
| 0x07 | One Bit Audio Sample Packet |
| 0x08 | DST Audio Packet |
| 0x09 1 | High Bitrate (HBR) Audio Stream Packet (IEC 61937) |
| 0x0A | Gamut Metadata Packet |
| 0x0B 1 | 3D Audio Sample Packet (LPCM Format Only) |
| 0x0C | One Bit 3D Audio Sample Packet |
| 0x0D 2 | Audio MetaData Packet |
| 0x80+InfoFrame Type | InfoFrame Packet |
| 0x00 | Reserved |
| 0x01 2 | Vendor-Specific 3 |
| 0x02 2 | Auxiliary Video Information (AVI) |
| 0x03 | Source Product Descriptor |
| 0x04 2 | Audio |
| 0x05 | MPEG Source |
| 0x06 | NTSC VBI |
| 0x07 2 | Dynamic Range and Mastering (HDR) |
|
|
In the HDMI 2.1 TX Subsystem driver, a common API is defined for sending auxiliary packets.
u32 XV_HdmiTxSs1_SendGenericAuxInfoframe(XV_HdmiTxSs1 *InstancePtr, void *AuxPtr);where,
- InstancePtr is a pointer to the HDMI 2.1 TX Subsystem instance.
- Aux is a 36 byte array contains the complete AUX packet.
The AUX packet data structure defined in the driver is:
typedef union {
u32 Data;
u8 Byte[4];
} XHdmiC_AuxHeader;
typedef union {
u32 Data[8];
u8 Byte[32];
} XHdmiC_AuxData;
typedef struct {
XHdmiC_AuxHeader Header;
XHdmiC_AuxData Data;
} XHdmiC_Aux;For packet types not highlighted in the previous table (MPEG Source, NTSC VBI), you can construct packets with respect to the specification, and send them using the same API call. In this case, you must calculate the CRC whenever needed and place the CRC at the right location so that the HDMI Sink can decode the packet.