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- Q : Is is possible to use AVB over a standard network adapter (without HW support)
- A : No, not for high fidelity Audio automotive or pro equipment.
- Although it is possible to apply the same algorithms with as reference a timer for SW timestamp, but that might induce one or more orders of magnitude of precision loss, that results in a different concepts of buffer dimensioning and so on.
- Q : ptp target precision (~ 5 ns)
- 5 ns ? 5 us ?
48 KHz => ~ 20 us
1, 2 samples ? => 50 us - produce a sample (3 ms), touch the screen (interrupt) => loop 2ms, 2 ms buffer (100 samples)
- 5 ns ? 5 us ?
- Latency (transmitter + network propagation + receiver)
- network propagation depends on number of switches e.g. 2 ms latency over 7 hops
- end to end latency (ADC → net → DAC) hop ~ 250 us
- 6 samples packets processing (48 KHz) every 125 us
- buffers go critical down to 1 sample...
- e.g. 5 us => 125 that means 4% more latency for 5 us precision in stead of 5 ns
- what are the latency requirements and which equipment needs which latency
- RNC AEC ANC Active Noise Cancelling (< 1ms) (Automotive - should not involve netwrok)
- musical instrument(end to end ~ 2 ms) (not Automotive- should not involve netwrok)
- Gaming ?
- playing smartphone instrument (10 ms) (Automotive infotainment - might involve network)
- streaming musing (1 s) (Automotive Infotainment - can involve network)
- Lip sync not problematic because none of the audio/video is real time, you can delay both stream with the same amount => sync 20~40 ms.
- cold start latency : is a different KPI than the sync delta of video audio => (~ 500 ms).
- Phase manipulation in case of audio zones
- problem starts if the different zones are played from different network devices
- Network stability, reduction of jitter
- => SRP Stream reservation protocol
AVB over RTP IP without HW
- => SRP Stream reservation protocol
- Renesas example on references, usage of OpenAvenu
- Avenu as open source but more reliable implementation than other existing ones
- Q : Steps to be taken for starting the SW
- Q : clock recovery algorithm, might recover smoother by catching up
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