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TOPIC: Synchronizing the playback and capture streams

Synchronizing the playback and capture streams 2 years 6 months ago #36421

  • stoltzo
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We have the USBstreamer connected to a Raspberry PI3 and are struggling with keeping the playback and capture streams running in sync at the same sample rate. As can be seen in the below information the momentary freq for playback is 47999Hz but for capture it is 48000Hz. We are working on integrating an acoustic echo-canceller and need the two streams to operate at the same frequency.

Does anyone know how to ensure that the streams run at the same rate?

Best
Tom

[email protected]:~ $ cat /proc/asound/card1/stream0
miniDSP USBStreamer at usb-3f980000.usb-1.5, high speed : USB Audio

Playback:
Status: Running
Interface = 1
Altset = 1
Packet Size = 360
Momentary freq = 47999 Hz (0x5.fff8)
Feedback Format = 16.16
Interface 1
Altset 1
Format: S32_LE
Channels: 10
Endpoint: 1 OUT (ASYNC)
Rates: 44100, 48000, 88200, 96000, 176400, 192000
Data packet interval: 125 us

Capture:
Status: Running
Interface = 2
Altset = 1
Packet Size = 360
Momentary freq = 48000 Hz (0x6.0000)
Interface 2
Altset 1
Format: S32_LE
Channels: 10
Endpoint: 2 IN (ASYNC)
Rates: 44100, 48000, 88200, 96000, 176400, 192000
Data packet interval: 125 us
Last Edit: 2 years 6 months ago by stoltzo.
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Synchronizing the playback and capture streams 2 years 6 months ago #36591

  • frnchfrgg
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IĀ also noticed that the "Momentary freq" of the input is never changing; shouldn't it vary depending on the incoming clock ? No device would be stable enough to never have a difference down to the last hertz...

By connecting the USBStreamer IN to its own OUT and selecting the ADAT clock, I noticed a slow diminution of the rate of play, which is sensible since there is no stable rate to sync to, but the momentary freq of the incoming stream is still reported to be exactly the one configured. Is it expected ?
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