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Encoder (line in)

An encoder takes audio from a USB line-in adapter and sends it to the network as an AES67 multicast stream: 24-bit (L24), 48 kHz, one packet per millisecond, stamped with the shared PTP clock.

Set up​

  1. Plug a USB line-in adapter into the board's USB host port.
  2. On the board's page, choose Encoder · line in under Settings.
  3. Set:
    • Stream name: what decoders, the matrix and Dante Controller show.
    • Multicast group: the address the stream is sent to. Each board starts on its own, 239.200. followed by the last two bytes of its MAC address as numbers: etherjax-ab12 sends to 239.200.171.18. The default is outside 239.69.0.0/16, the range Dante uses for its own AES67 streams. If another sender turns up on the same group, the encoder moves (see below).
    • RTP port: an even number, 1024 or above. 5004 is standard.
    • Channels: 1 to 8. The adapter's channels are mapped onto these: the channels they share are copied, and a mono adapter feeds both sides of a stereo stream.
    • Announce with SAP: leave on so decoders, Dante Controller and VLC can find the stream.
  4. Choose Save & reboot.

Check it​

  • Input levels (sent) shows the level of each channel as it is sent.
  • USB line in shows the adapter, its format, and Buffer (how much audio is waiting between USB and the network).
  • Stream shows the group and packet counts.
  • Clock (PTP) shows whether the board is the clock master (grandmaster) or following another one, and how far off it is. See clocks.

If another sender uses the group​

Two senders on one group and port play as one garbled stream on most receivers. Encoders watch for this, both in SAP announcements and among the other EtherJax boards. When an encoder finds another sender on its group, it:

  1. picks a free group: 239.201. and the same two MAC bytes, then 239.202., and so on, skipping any group already in use;
  2. sends there from the next packet, announces the new group at once, and saves it as its Multicast group;
  3. takes its decoders with it: a decoder playing this encoder follows the new announcement on its own. Dante receivers don't: subscribe them again in Dante Controller.

When both senders are EtherJax encoders, only one of them moves: the one with the higher IP address. Until it has moved, the encoder's health shows … also sends to this stream's group.

Boards set up before this release, still on the old shared default (239.200.83.1 or 239.69.83.1), switch to their own group when they start. Route the decoders that played them again, with Listen or in the matrix.

Listen without a decoder​

The stream's SDP description is at http://etherjax-XXXX.local/stream.sdp, which needs no password, so media players can open it directly:

vlc http://etherjax-XXXX.local/stream.sdp

Reboots and the stream list​

When an encoder restarts on purpose (a reboot, saved settings or a firmware update), it withdraws its SAP announcement first, so decoders drop it from their lists straight away instead of after a few minutes. It comes back under the same session, so decoders and Dante receivers playing it pick it up again.