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osmo-bts-trx: perform error concealment for FR frames 

When a bad voice frame is received, it is replaced by
a silence frame. This may cause unpleasant audio effects.

This change implements a functionality to craft a replacement
frame from the last known good frame using ECU implementation
from libosmocodec. At the moment, only FR is supported.

Depends: libosmocore I06a21f60db01bfe1c2b838f93866fad1d53fdcd1
Change-Id: Iae9e69a9578ae305bca42f834694af96a29084e6
This commit is contained in:
Philipp Maier 2017-12-06 18:08:38 +01:00
parent dd4a6518f2
commit 69d0d50677
2 changed files with 22 additions and 2 deletions
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6
include/osmo-bts/gsm_data_shared.h
View File

@ -5,6 +5,7 @@
#include <stdbool.h>
#include <stdint.h>
#include <osmocom/codec/ecu.h>
#include <osmocom/core/timer.h>
#include <osmocom/core/bitvec.h>
#include <osmocom/core/statistics.h>
@ -316,6 +317,11 @@ struct gsm_lchan {
} ms_power_ctrl;
struct msgb *pending_rel_ind_msg;
/* ECU (Error Concealment Unit) state */
union {
struct osmo_ecu_fr_state fr;
} ecu_state;
};
extern const struct value_string lchan_ciph_state_names[];

18
src/osmo-bts-trx/scheduler_trx.c
View File

@ -31,6 +31,7 @@
#include <osmocom/core/msgb.h>
#include <osmocom/core/talloc.h>
#include <osmocom/codec/codec.h>
#include <osmocom/codec/ecu.h>
#include <osmocom/core/bits.h>
#include <osmocom/gsm/a5.h>
#include <osmocom/coding/gsm0503_coding.h>
@ -964,6 +965,7 @@ int rx_tchf_fn(struct l1sched_trx *l1t, uint8_t tn, uint32_t fn,
uint8_t tch_data[128]; /* just to be safe */
int rc, amr = 0;
int n_errors, n_bits_total;
bool bfi_flag = false;
struct gsm_lchan *lchan =
get_lchan_by_chan_nr(l1t->trx, trx_chan_desc[chan].chan_nr | tn);
@ -1054,11 +1056,13 @@ int rx_tchf_fn(struct l1sched_trx *l1t, uint8_t tn, uint32_t fn,
if (rc < 0) {
LOGL1S(DL1P, LOGL_NOTICE, l1t, tn, chan, fn, "Received bad data (%u/%u)\n",
fn % l1ts->mf_period, l1ts->mf_period);
bfi_flag = true;
goto bfi;
}
if (rc < 4) {
LOGL1S(DL1P, LOGL_NOTICE, l1t, tn, chan, fn, "Received bad data (%u/%u) "
"with invalid codec mode %d\n", fn % l1ts->mf_period, l1ts->mf_period, rc);
bfi_flag = true;
goto bfi;
}
@ -1075,8 +1079,14 @@ bfi:
case GSM48_CMODE_SPEECH_V1: /* FR */
if (lchan->tch.dtx.ul_sid)
return 0; /* DTXu: pause in progress */
memset(tch_data, 0, GSM_FR_BYTES);
tch_data[0] = 0xd0;
/* Perform error concealment if possible */
rc = osmo_ecu_fr_conceal(&lchan->ecu_state.fr, tch_data);
if (rc) {
memset(tch_data, 0, GSM_FR_BYTES);
tch_data[0] = 0xd0;
}
rc = GSM_FR_BYTES;
break;
case GSM48_CMODE_SPEECH_EFR: /* EFR */
@ -1104,6 +1114,10 @@ bfi:
if (rsl_cmode != RSL_CMOD_SPD_SPEECH)
return 0;
/* Reset ECU with a good frame */
if (!bfi_flag && tch_mode == GSM48_CMODE_SPEECH_V1)
osmo_ecu_fr_reset(&lchan->ecu_state.fr, tch_data);
/* TCH or BFI */
return _sched_compose_tch_ind(l1t, tn, (fn + GSM_HYPERFRAME - 7) % GSM_HYPERFRAME, chan,
tch_data, rc);