Protocole Diretta

[Bear]

Bonjour,

Pour avoir des 'jumbo frames' avec DirettaAlsa, Yu m'indique qu'il faut mettre

Code :

TargetProfileLimitTime=0

dans setting.inf

Ça marche:

Code :

07:27:56.628366 00:1b:21:76:ae:ba (oui DCBX) > 00:e0:4c:38:03:cd (oui Unknown), ethertype Unknown (0x88b6), length 9024

À noter le nouvel 'ethertype' déposé par Yu auprès de l'IEEE: 0x88b6 pour Diretta Direct Stream. Yu a fait un long post en Japonais sur Facebook pour expliquer tout cela. En voici la traduction en Anglais (synthétisée par Clause Sonnet 4.5):

Understanding Diretta's MS Modes - Technical Breakdown

This is a summary of Yu's (Diretta developer) explanation of the protocol's evolution:

MS Modes (Multi-Stream Modes) - Evolution of Data Format

MS Mode 1:

• Uses IPv6/UDP packets
  
• 16-byte Diretta header + audio data
  
• 1 byte control data at the end
  
• Multiple UDP ports for stream sorting
  

MS Mode 2:

• Moved control data to front (2 bytes) for efficiency
  
• Optimized for DPDK (Data Plane Development Kit) processing
  
• Better 64-bit alignment
  

MS Mode 3 (DDS - Diretta Direct Stream):

• Major change: Eliminates IPv4/IPv6 entirely
  
• Uses raw Ethernet Frames instead of IP packets
  
• Removes 56 bytes of overhead (IPv6/UDP headers)
  
• 2 bytes control data, 64-bit aligned both ways
  
• Applying for official EtherType registration (~3 month process)
  

Size/Transmission Strategy

• Supports various packet sizes (JumboFrame capable)
  
• Size × Count: Size = data payload, Count = number of transmissions
  
• Splits large data into multiple frames if exceeding MTU
  
• Two adjustment methods:
  
  • Traditional: DAC (Target) declares parameters, Host follows
    
  • Current: Host-controlled (user/manufacturer requested)
    

Configuration

• TargetProfileLimitTime: Minimum sending period Host can operate
  
• Setting to "0" disables Target profile, uses Host settings
  
• ThreadMode controls OS threading behavior
  
• GUI configuration now available in Diretta ASIO Driver 3
  

Key Distinction

Yu emphasizes: MS Mode = packet structure, Host settings = transmission method. These are separate concepts.

The main innovation is Mode 3 eliminating IP overhead for lower latency/jitter in audio streaming.