Attention is currently required from: fixeria.

falconia has posted comments on this change by fixeria. ( 
https://gerrit.osmocom.org/c/osmo-bts/+/38751?usp=email )

Change subject: csd_v110: handle TCH/F14.4
......................................................................


Patch Set 3:

(2 comments)

Commit Message:

https://gerrit.osmocom.org/c/osmo-bts/+/38751/comment/745b4206_41594baa?usp=email
 :
PS3, Line 15: E-TRAU frames (spoken over the air)
Nitpick: E-TRAU frames are not spoken over the air, they are spoken over E1 
Abis. However, the block of 290 bits is exactly the same between E-TRAU and the 
air interface, which is why the same RAA' functions work here as well as 
trau2rtp and rtp2trau functions in libosmotrau, and can be unit-tested for 
exact match against a historical hardware TRAU.

Perhaps reword like this: "which converts between between 290-bit blocks used 
on Um and Abis-E1 interfaces (E-TRAU frames on the latter) and A-TRAU frames 
spoken over the A interface."


File src/common/csd_v110.c:

https://gerrit.osmocom.org/c/osmo-bts/+/38751/comment/d1524b0c_ca1bd39f?usp=email
 :
PS3, Line 113: memset(&ra_bits[0], 0x01, sizeof(ra_bits));
This code won't have the desired effect: `ra_bits[]` is the output buffer for 
`osmo_csd144_to_atrau_bits()`, not the input. Thus the memset itself will have 
no effect whatsoever (the buffer will be fully overwritten two lines later), 
while the A-TRAU encoding function will read from `&data[0]` and `&data[2]`, 
i.e., from non-existing memory, aka an out-of-bound read - obviously bad.

We'll need a separate on-stack temporary buffer to hold the needed 290 dummy 
bits - yes, I know, it's ugly. Alternatively, perhaps have a const array that 
hard-codes the fixed A-TRAU output from all-1s data and M bits, and C5=1 - 
whichever you feel more comfortable implementing.



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