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Support of VW / full rate #13

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mweyland opened this issue Oct 15, 2015 · 0 comments
Closed

Support of VW / full rate #13

mweyland opened this issue Oct 15, 2015 · 0 comments

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@mweyland
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The VW mode sends AMBE2+ frames as follows according to the spec:

The transmission rate of the voice signal must be 7.2 kbps or less including the error
correction code. Voice encoding follows the standards stipulated for a frame size of 20 ms
(144 bit), voice code of 4.4 kbps, error correction code of 2.8 kbps Digital Voice Systems, Inc’s
AMBE+2 TM Enhanced Full-Rate (7200 bps).

Check if mbelib supports that. If not, this is probably a lost cause. Also see #12.

mweyland pushed a commit that referenced this issue Mar 28, 2016
… applying FEC.

Because a crude basic VW mode is now implemented (see issue #13).
mweyland pushed a commit that referenced this issue Mar 28, 2016
This feature branch introduces preliminary decoding of the VW (full rate) mode.
This contribution would not have been possible without Sylvain Munaut, who
taught me a number of amazing tricks in the process. The feature branch entails
the following changes:

1. New block YSF FR VCH Decoder
   This block expects a stream of bits. 144 bits of those bits are treated as
   one AMBE frame and converted into something that mbelib can process. We are
   using mbelib's IMBE decoder because the rate stipulated by the Yaesu spec is
   supposed to be backwards compatible to that. This block should apply FEC
   eventually, but currently does not.

2. Changes to the deframer and planner in order to recognize and process packets
   in VW mode.

3. Changes to the ysf_rx.grc example flow graph: A new path was added to receive
   and play voice transmissions in VW mode.

4. Change to the mbelib block: The labels, text strings and code contained the
   FEC size. This was wrong and misleading because we are supposed to do all the
   FEC-work outside of that block. Once we pass a MBE frame to the block, it
   does not have any FEC anymore. We should therefore not imply otherwise.

The merge fixes issue #13.
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