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2 ) cross ECU interactions (remote control, including comparison with remote servers interaction)

3 ) Audio effects

AVB Network Audio Synchronization

workshop 26/11/2020

  • ECUs spread across a network have different clocks (CPU, network, audio,...)
  • Clock drift, oscillators accuracy (1/day => 10 us/sec => for 44.1KHz one sample loss each 2 sec)
  • Solution run SW on synchronized time
  • how to synchronize time ?
  • asynchronous resampling needed as the speakers DAC always need to be synchronous to their own clock
  • PTP => Wall clock (e.g. +-500 ns to master clock)
    • media clock recovery, second layer (IEEE 1722 frame protocol, presentation time stamp taken as reference)
    • each takes as reference and reproduces a local clock that is in synch with the wall clock
  • PTP does not solve jitter problem => how to compensate jitter ? => increase buffer size => increase latency
  • Clock recovery. Or how to generate a clock when all we get from ptp is sporadic info about delay status + or -
  • real-time accuracy vs latency
  • TNS = Sync + Latency + Reliability, ... (SRP Stream Reservation Protocol)
  • Qav (IEEE 802.1Qav: Forwarding and Queuing for Time-Sensitive Streams)
    • issues of packet loss / drop
    • constraints for each source
    • spread out of stream (traffic shaping)
  • What if we cannot synchronize the time ?
    • Mixing of different streaming sources (can't follow multiple clocks)
    • Asynchronous domain crossing => latency
    • Synchronous resampling (format conversion only for already synchronized clocks 48KHz => 32 KHz)
  • AVB : Routing only => cable connection for a continuous audio stream => No media control, no start, no pause, no skip,...
    • separate control protocol (someip,... although TNS has some but automotive using someip)
  • AVB Software
    • Kernel module (Steve => RENESAS_RCH3M3M3NE3_EAVB_AVBStreaming_UME_v2.00 page 5)
    • (RENESAS_RCH3M3M3NE3_EAVB_LauncherApplication_ANE_v2.00 page 10)
  • ALSA to AVB (RENESAS_RCH3M3M3NE3_EAVB_MSE_UME_v2.00 page 4)
  • Existing open source AVB linux integrations (HW dependent topic)

...

=> CVII common standard initiative

A2B Network Audio

A²B

I²C
I²S

Android A2B/ALSA driver
Android => (I2C,I2S_1,I2S_2) => (A2B devKit) <=> (A2B remote1),(A2B remote2)