Attention is currently required from: falconia.

fixeria has posted comments on this change. ( 
https://gerrit.osmocom.org/c/osmo-bts/+/33069 )

Change subject: trx TCH DL: transmit invalid speech frames instead of dummy 
FACCH
......................................................................


Patch Set 1:

(2 comments)

File src/osmo-bts-trx/sched_lchan_tchf.c:

https://gerrit.osmocom.org/c/osmo-bts/+/33069/comment/0096fad3_a0351a92
PS1, Line 500: what is the correct BTS Tx behavior for frame
             :           * gaps in TCH/AFS
I guess we could indicate a bad frame via AMR's in-band signalling? Just an 
idea.
IIRC, this is what ip.access nanoBTS does in the absence of RTP frames.
See also: https://osmocom.org/issues/4823.


https://gerrit.osmocom.org/c/osmo-bts/+/33069/comment/db2c9660_e3ed2799
PS1, Line 505: gsm0503_tch_fr_encode
I suggest using a switch here:

```
switch (tch_mode) {
case GSM48_CMODE_SPEECH_V1:
case GSM48_CMODE_SPEECH_EFR:
    rc = gsm0503_tch_fr_encode(*bursts_p, NULL, 0, 1);
    if (rc == 0)
        break;
    /* fall-through */
default:
    gsm0503_tch_fr_encode(*bursts_p, dummy, sizeof(dummy), 1);
    chan_state->dl_facch_bursts = 8;
}
```

The reason why I am suggesting this, specifically the fall-through if `rc != 
0`, is that the user may be running an older version of libosmocore, predating 
your patch `Iade3310e16b906efb6892d28f474a0d15204e861`. In this case 
`gsm0503_tch_fr_encode()` would return -1 and we will fall-back to FACCH rather 
than sending garbage.



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Gerrit-Project: osmo-bts
Gerrit-Branch: master
Gerrit-Change-Id: I78106802a0aa4af39859c75d29fe0e77037899fe
Gerrit-Change-Number: 33069
Gerrit-PatchSet: 1
Gerrit-Owner: falconia <[email protected]>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: pespin <[email protected]>
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Gerrit-Comment-Date: Mon, 29 May 2023 12:10:19 +0000
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