diff options
| author | Vadim Yanitskiy <vyanitskiy@sysmocom.de> | 2023-05-26 01:38:23 +0700 |
|---|---|---|
| committer | Vadim Yanitskiy <vyanitskiy@sysmocom.de> | 2023-05-26 02:48:21 +0700 |
| commit | b04d59e9973f372ed863be54a250a91eae1a1fd1 (patch) | |
| tree | 39d41a2583b01d15212d3b2cce250ddf0e1c0127 /src/coding | |
| parent | 31f761f7c112a30191be04391dbbbe7cbb377634 (diff) | |
coding: fix _tch_csd_burst_map(): do not overwrite FACCH
As was demonstrated in the unit test [1], FACCH bitstealing does not
work as expected in conjunction CSD specific encoding functions.
The problem is in _tch_csd_burst_map(): we don't check the stealing
flags hu(B) and hl(B) and overwrite both odd and even numbered bits
unconditionally. Even worse, we reset these stealing flags to 0.
* Do not overwrite the hu(B) and hl(B) flags.
* Copy *even* numbered bits only if hu(B) is not set.
* Copy *odd* numbered bits only if hl(B) is not set.
Change-Id: Ib5395c70e3e725469c18ff7d4c47c62ddfdbd55d
Related: [1] Idc6decec3b84981d2aab4e27caab9ad65180f945
Related: OS#1572
Diffstat (limited to 'src/coding')
| -rw-r--r-- | src/coding/gsm0503_coding.c | 20 |
1 files changed, 15 insertions, 5 deletions
diff --git a/src/coding/gsm0503_coding.c b/src/coding/gsm0503_coding.c index 5badbd09..a34cd923 100644 --- a/src/coding/gsm0503_coding.c +++ b/src/coding/gsm0503_coding.c @@ -3298,13 +3298,23 @@ int gsm0503_sch_encode(ubit_t *burst, const uint8_t *sb_info) static inline void _tch_csd_burst_map(ubit_t *burst, const ubit_t *iB) { - for (unsigned int i = 0; i < 57; i++) { - burst[i] |= iB[i]; - burst[59 + i] |= iB[57 + i]; + unsigned int i; + + /* hu(B): copy *even* numbered bits if not stolen by FACCH */ + if (burst[58] == 0) { + for (i = 0; i < 57; i += 2) + burst[i] |= iB[i]; + for (i = 58; i < 114; i += 2) + burst[i + 2] |= iB[i]; } - burst[57] = 0; /* hl(B) */ - burst[58] = 0; /* hu(B) */ + /* hl(B): copy *odd* numbered bits if not stolen by FACCH */ + if (burst[57] == 0) { + for (i = 1; i < 57; i += 2) + burst[i] |= iB[i]; + for (i = 57; i < 114; i += 2) + burst[i + 2] |= iB[i]; + } } /*! Perform channel encoding of a TCH/F9.6 channel as per section 3.3. |