libosmocodec: implement ECU (Error Concealment Unit) for FR

When a bad GSM voice frame is received, it's being 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. Currently, only FR is
supported, support for other codecs may be added latter.

Change-Id: I06a21f60db01bfe1c2b838f93866fad1d53fdcd1

2 files changed, 338 insertions, 0 deletions

diff --git a/tests/codec/codec_ecu_fr_test.c b/tests/codec/codec_ecu_fr_test.c
new file mode 100644
index 00000000..0fdc489d
--- /dev/null
+++ b/tests/codec/codec_ecu_fr_test.c
@@ -0,0 +1,146 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+
+#include <osmocom/core/bitvec.h>
+#include <osmocom/core/utils.h>
+
+#include <osmocom/codec/codec.h>
+#include <osmocom/codec/ecu.h>
+
+/* Set with sample full-rate voice frames and some intentional dropouts */
+static const char *fr_frames_hex[] = {
+	"d9aa93ae63de00471a91b95b8660471392b4a2daa037628f391c624039258dc723",
+	"d8eb83699a66c036ec89b7246e6034dc8d48948620589b7256e3a6603b2371b8da",
+	"d967abaa1cbe4035238da6ace4c036d46ec69ba600391c4eb8a2b040591c6a3924",
+	"d8e8a42662c240472469b91bd2e0452291b6dba600495b8e38dcb020491a71c91b",
+	"da2aac1ddbb00036e46e26dcec6039138db923822047137248e3560048e38dc8e3",
+	"d929ab2a9b5240395b6dc72ba020469c8d551c5440349c9148e36a4036a372471b",
+	"d9eb93215bb8a0271c69c724682036db71c71a94a0372491b72bee4044eb71b923",
+	"d9ab9aa19abc40391b6e5ae2ee40471b91c6dbe820492291b8e4b84036e47238db",
+	"d96b9be9db782044e371b55cb200389491c69b8ea034e271c8d3808038ec6db8e3",
+	"d9aa9365e3f060375c6db6ebc4c02764b1c51b78a0571c91a723de6049248dc8dd",
+	"BAD",
+	"d9ea9c219ce60046e38d3724e0c034e56e36eb7e0038d471b8dcb260491b8dbb23",
+	"d9e89be9d9e0a0391b6dd6a4624029247138e3a2a04713922524de0036db69d91c",
+	"d9699422a2b6a048dd90c91c6a802b6259395c8880575b4a58e4ac20269d7248d4",
+	"d967ac5b1baae0371c71b8ab9c804a9e8e58a55a8038626ec8dcb640395c7244dc",
+	"d9e8a3e262e68027638db52b88a038634e471a7ec049136e3b1bc8402923adcad2",
+	"d8eab36e1bbe0046e34d491b608035137658d3524044e48e375cdac0472b9238d4",
+	"d9689ba5e3d260491b516adb5e4027256e27227ee0351c8e549a5c60492471971b",
+	"BAD",
+	"BAD",
+	"d8e6a2e1d3d2605b1376c8d35280392451391cbc80392a71b6db8aa049238dc8ab",
+	"d9a87ba1a3982048eb8a471cac00472b4e391bbc40292489b71cc200495b8d3ae3",
+	"d9278b2a1ba4c0475b8dc722d6e0491b5228da70204ae36dc71d94a056a29236e3",
+	"d9ec9be2129520392335598c50c04b5bad3d4ba680789b69df5a5aa0469cd1b4da",
+	"d8ea932623e660669b8e4a9dd8a03aa32a76e466e028d396cc9bbe4047256dc8e5",
+	"d96a94215aa0403aab713f22e8e024e68db91ab6a027abd1a55b6e804aec9146e4",
+	"d867ac21e270a0350d6ac91a724037247246d2a6c0396c89d6dc562049244e48d5",
+	"d8a9b460d3b48026a4ad471b7c20452491b69bbc803ae48db722ee00292491a8db",
+	"d928a3e1d3b24036e37244abf02047634d371b74c047637148a29ac03b234e38e3",
+	"d9ab9b21d2e0c0471c693aec54e044dbae46dc7c20391badb724ee8038e469bb15",
+	"d9a99361a276403b1a6ad6dcd40026e489c8e3bc40371c4dc564e2c036e28eb963",
+	"BAD",
+	"BAD",
+	"BAD",
+	"BAD",
+	"BAD",
+	"BAD",
+	"d92c8b6d5aee4034ebb22724862047145634a5c0a038e371b8e4a880485c89dd25",
+	"d8e78b29e3c6c038dba9d91beca04723ad491cda80471471b6ec7ae03b1396b91b",
+	"d8a78b25e37a0022dd8a46dc68a0351bad391bde2046e56dd8dc96c038e396d89b",
+	"d8a88c255ab6e038e38e48dbde8038ad8dc8db8ec0376372b564b44038e49234dc",
+	"d9708ce6a39ce049646646a2c1a0272496b29a66c037db562863ace0795b55b2e3",
+	"d8ee9bea5ae4003ae371b713eae05adc91995a5ea064dcc9571e786026ed51c52c",
+	"d9299421d2944036ed69b8e572a048e36d551cd480571d4ec95be680356c69c763",
+	"d92aab696190c046e26e392cae0026a376a8dc662048d291b75b54c04ad3ae3b1b",
+	"d8e7a469627a6038e289cb1baca0569b8db6dddec026dc8e38e5dc803722722d23",
+	"d8a88c299b64c03a548a58e37420272c6dd76b92c0471c9236dbc0e0551c71c713",
+	"BAD",
+	"d7299c19a3be8024e58ea7a49f20a522963ad976e0a76ecd92b38500cb62aa4c94",
+	"d7eb6c6262eee02b2c42e79a60a0aa55aed68a7f00ad358e10fad960e55a39396d",
+	"d970858dd2ab61d91355ebc15ca1a6a7ca48a05cc0dae66f2523c2a1bad3825daa",
+	"d8f0844a23ad20da50d6de025e81c37392b9039cc0c764c1bd1e94c1b699736a98",
+	"d9708ce6a39ce049646646a2c1a0272496b29a66c037db562863ace0795b55b2e3",
+	"d9299421d2944036ed69b8e572a048e36d551cd480571d4ec95be680356c69c763",
+	"d9299421d2944036ed69b8e572a048e36d551cd480571d4ec95be680356c69c763",
+	"d9299421d2944036ed69b8e572a048e36d551cd480571d4ec95be680356c69c763",
+	"d2577a1cda50004924924924500049249249245000492492492450004923924924",
+	NULL
+};
+
+/* Example of a good frame */
+static const char *sample_frame_hex = \
+	"d9ec9be212901f802335598c501f805bad3d4ba01f809b69df5a501f809cd1b4da";
+
+/**
+ * Start with a good voice frame and then simulate 20 consecutive bad frames,
+ * watching how the error concealment decreases the XMAXC parameters.
+ */
+void test_fr_concealment(void)
+{
+	struct osmo_ecu_fr_state state;
+	uint8_t frame[GSM_FR_BYTES];
+	int i, rc;
+
+	/* Parse frame from string to hex */
+	osmo_hexparse(sample_frame_hex, frame, GSM_FR_BYTES);
+
+	printf("Start with: %s\n", sample_frame_hex);
+
+	/* Reset the ECU with the proposed known good frame */
+	osmo_ecu_fr_reset(&state, frame);
+
+	/* Now pretend that we do not receive any good frames anymore */
+	for (i = 0; i < 20; i++) {
+		rc = osmo_ecu_fr_conceal(&state, frame);
+		OSMO_ASSERT(rc == 0);
+
+		printf("conceal: %02i, result: %s\n",
+			i, osmo_hexdump_nospc(frame, GSM_FR_BYTES));
+	}
+}
+
+/* Simulate a real life situation: voice frames with a few dropouts */
+void test_fr_concealment_realistic()
+{
+	struct osmo_ecu_fr_state state;
+	uint8_t frame[GSM_FR_BYTES];
+	unsigned int frame_len;
+	int rc, i = 0;
+
+	while (fr_frames_hex[i] != NULL) {
+		/* Debug print */
+		printf("Frame No. %03i:\n", i);
+
+		/* Good or bad frame? */
+		frame_len = strlen(fr_frames_hex[i]) / 2;
+		if (frame_len == GSM_FR_BYTES) {
+			printf(" * input:  %s\n", fr_frames_hex[i]);
+			osmo_hexparse(fr_frames_hex[i], frame, GSM_FR_BYTES);
+			osmo_ecu_fr_reset(&state, frame);
+		} else {
+			printf(" * input:  (bad)\n");
+			memset(frame, 0x00, GSM_FR_BYTES);
+			rc = osmo_ecu_fr_conceal(&state, frame);
+			OSMO_ASSERT(rc == 0);
+		}
+
+		/* Print result */
+		printf(" * output: %s\n",
+			osmo_hexdump_nospc(frame, GSM_FR_BYTES));
+
+		/* Go to the next frame */
+		i++;
+	}
+}
+
+int main(int argc, char **argv)
+{
+	/* Perform actual tests */
+	test_fr_concealment();
+	test_fr_concealment_realistic();
+
+	return 0;
+}
diff --git a/tests/codec/codec_ecu_fr_test.ok b/tests/codec/codec_ecu_fr_test.ok
new file mode 100644
index 00000000..6e200994
--- /dev/null
+++ b/tests/codec/codec_ecu_fr_test.ok
@@ -0,0 +1,192 @@
+Start with: d9ec9be212901f802335598c501f805bad3d4ba01f809b69df5a501f809cd1b4da
+conceal: 00, result: d9ec9be212901f802335598c501f805bad3d4ba01f809b69df5a501f809cd1b4da
+conceal: 01, result: d9ec9be212901d802335598c501d805bad3d4ba01d809b69df5a501d809cd1b4da
+conceal: 02, result: d9ec9be212901b802335598c501b805bad3d4ba01b809b69df5a501b809cd1b4da
+conceal: 03, result: d9ec9be2129019802335598c5019805bad3d4ba019809b69df5a5019809cd1b4da
+conceal: 04, result: d9ec9be2129017802335598c5017805bad3d4ba017809b69df5a5017809cd1b4da
+conceal: 05, result: d9ec9be2129015802335598c5015805bad3d4ba015809b69df5a5015809cd1b4da
+conceal: 06, result: d9ec9be2129013802335598c5013805bad3d4ba013809b69df5a5013809cd1b4da
+conceal: 07, result: d9ec9be2129011802335598c5011805bad3d4ba011809b69df5a5011809cd1b4da
+conceal: 08, result: d9ec9be212900f802335598c500f805bad3d4ba00f809b69df5a500f809cd1b4da
+conceal: 09, result: d9ec9be212900d802335598c500d805bad3d4ba00d809b69df5a500d809cd1b4da
+conceal: 10, result: d9ec9be212900b802335598c500b805bad3d4ba00b809b69df5a500b809cd1b4da
+conceal: 11, result: d9ec9be2129009802335598c5009805bad3d4ba009809b69df5a5009809cd1b4da
+conceal: 12, result: d9ec9be2129007802335598c5007805bad3d4ba007809b69df5a5007809cd1b4da
+conceal: 13, result: d9ec9be2129005802335598c5005805bad3d4ba005809b69df5a5005809cd1b4da
+conceal: 14, result: d9ec9be2129003802335598c5003805bad3d4ba003809b69df5a5003809cd1b4da
+conceal: 15, result: d9ec9be2129001802335598c5001805bad3d4ba001809b69df5a5001809cd1b4da
+conceal: 16, result: d00000000000000000000000000000000000000000000000000000000000000000
+conceal: 17, result: d00000000000000000000000000000000000000000000000000000000000000000
+conceal: 18, result: d00000000000000000000000000000000000000000000000000000000000000000
+conceal: 19, result: d00000000000000000000000000000000000000000000000000000000000000000
+Frame No. 000:
+ * input:  d9aa93ae63de00471a91b95b8660471392b4a2daa037628f391c624039258dc723
+ * output: d9aa93ae63de00471a91b95b8660471392b4a2daa037628f391c624039258dc723
+Frame No. 001:
+ * input:  d8eb83699a66c036ec89b7246e6034dc8d48948620589b7256e3a6603b2371b8da
+ * output: d8eb83699a66c036ec89b7246e6034dc8d48948620589b7256e3a6603b2371b8da
+Frame No. 002:
+ * input:  d967abaa1cbe4035238da6ace4c036d46ec69ba600391c4eb8a2b040591c6a3924
+ * output: d967abaa1cbe4035238da6ace4c036d46ec69ba600391c4eb8a2b040591c6a3924
+Frame No. 003:
+ * input:  d8e8a42662c240472469b91bd2e0452291b6dba600495b8e38dcb020491a71c91b
+ * output: d8e8a42662c240472469b91bd2e0452291b6dba600495b8e38dcb020491a71c91b
+Frame No. 004:
+ * input:  da2aac1ddbb00036e46e26dcec6039138db923822047137248e3560048e38dc8e3
+ * output: da2aac1ddbb00036e46e26dcec6039138db923822047137248e3560048e38dc8e3
+Frame No. 005:
+ * input:  d929ab2a9b5240395b6dc72ba020469c8d551c5440349c9148e36a4036a372471b
+ * output: d929ab2a9b5240395b6dc72ba020469c8d551c5440349c9148e36a4036a372471b
+Frame No. 006:
+ * input:  d9eb93215bb8a0271c69c724682036db71c71a94a0372491b72bee4044eb71b923
+ * output: d9eb93215bb8a0271c69c724682036db71c71a94a0372491b72bee4044eb71b923
+Frame No. 007:
+ * input:  d9ab9aa19abc40391b6e5ae2ee40471b91c6dbe820492291b8e4b84036e47238db
+ * output: d9ab9aa19abc40391b6e5ae2ee40471b91c6dbe820492291b8e4b84036e47238db
+Frame No. 008:
+ * input:  d96b9be9db782044e371b55cb200389491c69b8ea034e271c8d3808038ec6db8e3
+ * output: d96b9be9db782044e371b55cb200389491c69b8ea034e271c8d3808038ec6db8e3
+Frame No. 009:
+ * input:  d9aa9365e3f060375c6db6ebc4c02764b1c51b78a0571c91a723de6049248dc8dd
+ * output: d9aa9365e3f060375c6db6ebc4c02764b1c51b78a0571c91a723de6049248dc8dd
+Frame No. 010:
+ * input:  (bad)
+ * output: d9aa9365e3f060375c6db6ebc4c02764b1c51b78a0571c91a723de6049248dc8dd
+Frame No. 011:
+ * input:  d9ea9c219ce60046e38d3724e0c034e56e36eb7e0038d471b8dcb260491b8dbb23
+ * output: d9ea9c219ce60046e38d3724e0c034e56e36eb7e0038d471b8dcb260491b8dbb23
+Frame No. 012:
+ * input:  d9e89be9d9e0a0391b6dd6a4624029247138e3a2a04713922524de0036db69d91c
+ * output: d9e89be9d9e0a0391b6dd6a4624029247138e3a2a04713922524de0036db69d91c
+Frame No. 013:
+ * input:  d9699422a2b6a048dd90c91c6a802b6259395c8880575b4a58e4ac20269d7248d4
+ * output: d9699422a2b6a048dd90c91c6a802b6259395c8880575b4a58e4ac20269d7248d4
+Frame No. 014:
+ * input:  d967ac5b1baae0371c71b8ab9c804a9e8e58a55a8038626ec8dcb640395c7244dc
+ * output: d967ac5b1baae0371c71b8ab9c804a9e8e58a55a8038626ec8dcb640395c7244dc
+Frame No. 015:
+ * input:  d9e8a3e262e68027638db52b88a038634e471a7ec049136e3b1bc8402923adcad2
+ * output: d9e8a3e262e68027638db52b88a038634e471a7ec049136e3b1bc8402923adcad2
+Frame No. 016:
+ * input:  d8eab36e1bbe0046e34d491b608035137658d3524044e48e375cdac0472b9238d4
+ * output: d8eab36e1bbe0046e34d491b608035137658d3524044e48e375cdac0472b9238d4
+Frame No. 017:
+ * input:  d9689ba5e3d260491b516adb5e4027256e27227ee0351c8e549a5c60492471971b
+ * output: d9689ba5e3d260491b516adb5e4027256e27227ee0351c8e549a5c60492471971b
+Frame No. 018:
+ * input:  (bad)
+ * output: d9689ba5e3d260491b516adb5e4027256e27227ee0351c8e549a5c60492471971b
+Frame No. 019:
+ * input:  (bad)
+ * output: d00000000000000000000000000000000000000000000000000000000000000000
+Frame No. 020:
+ * input:  d8e6a2e1d3d2605b1376c8d35280392451391cbc80392a71b6db8aa049238dc8ab
+ * output: d8e6a2e1d3d2605b1376c8d35280392451391cbc80392a71b6db8aa049238dc8ab
+Frame No. 021:
+ * input:  d9a87ba1a3982048eb8a471cac00472b4e391bbc40292489b71cc200495b8d3ae3
+ * output: d9a87ba1a3982048eb8a471cac00472b4e391bbc40292489b71cc200495b8d3ae3
+Frame No. 022:
+ * input:  d9278b2a1ba4c0475b8dc722d6e0491b5228da70204ae36dc71d94a056a29236e3
+ * output: d9278b2a1ba4c0475b8dc722d6e0491b5228da70204ae36dc71d94a056a29236e3
+Frame No. 023:
+ * input:  d9ec9be2129520392335598c50c04b5bad3d4ba680789b69df5a5aa0469cd1b4da
+ * output: d9ec9be2129520392335598c50c04b5bad3d4ba680789b69df5a5aa0469cd1b4da
+Frame No. 024:
+ * input:  d8ea932623e660669b8e4a9dd8a03aa32a76e466e028d396cc9bbe4047256dc8e5
+ * output: d8ea932623e660669b8e4a9dd8a03aa32a76e466e028d396cc9bbe4047256dc8e5
+Frame No. 025:
+ * input:  d96a94215aa0403aab713f22e8e024e68db91ab6a027abd1a55b6e804aec9146e4
+ * output: d96a94215aa0403aab713f22e8e024e68db91ab6a027abd1a55b6e804aec9146e4
+Frame No. 026:
+ * input:  d867ac21e270a0350d6ac91a724037247246d2a6c0396c89d6dc562049244e48d5
+ * output: d867ac21e270a0350d6ac91a724037247246d2a6c0396c89d6dc562049244e48d5
+Frame No. 027:
+ * input:  d8a9b460d3b48026a4ad471b7c20452491b69bbc803ae48db722ee00292491a8db
+ * output: d8a9b460d3b48026a4ad471b7c20452491b69bbc803ae48db722ee00292491a8db
+Frame No. 028:
+ * input:  d928a3e1d3b24036e37244abf02047634d371b74c047637148a29ac03b234e38e3
+ * output: d928a3e1d3b24036e37244abf02047634d371b74c047637148a29ac03b234e38e3
+Frame No. 029:
+ * input:  d9ab9b21d2e0c0471c693aec54e044dbae46dc7c20391badb724ee8038e469bb15
+ * output: d9ab9b21d2e0c0471c693aec54e044dbae46dc7c20391badb724ee8038e469bb15
+Frame No. 030:
+ * input:  d9a99361a276403b1a6ad6dcd40026e489c8e3bc40371c4dc564e2c036e28eb963
+ * output: d9a99361a276403b1a6ad6dcd40026e489c8e3bc40371c4dc564e2c036e28eb963
+Frame No. 031:
+ * input:  (bad)
+ * output: d9a99361a276403b1a6ad6dcd40026e489c8e3bc40371c4dc564e2c036e28eb963
+Frame No. 032:
+ * input:  (bad)
+ * output: d00000000000000000000000000000000000000000000000000000000000000000
+Frame No. 033:
+ * input:  (bad)
+ * output: d00000000000000000000000000000000000000000000000000000000000000000
+Frame No. 034:
+ * input:  (bad)
+ * output: d00000000000000000000000000000000000000000000000000000000000000000
+Frame No. 035:
+ * input:  (bad)
+ * output: d00000000000000000000000000000000000000000000000000000000000000000
+Frame No. 036:
+ * input:  (bad)
+ * output: d00000000000000000000000000000000000000000000000000000000000000000
+Frame No. 037:
+ * input:  d92c8b6d5aee4034ebb22724862047145634a5c0a038e371b8e4a880485c89dd25
+ * output: d92c8b6d5aee4034ebb22724862047145634a5c0a038e371b8e4a880485c89dd25
+Frame No. 038:
+ * input:  d8e78b29e3c6c038dba9d91beca04723ad491cda80471471b6ec7ae03b1396b91b
+ * output: d8e78b29e3c6c038dba9d91beca04723ad491cda80471471b6ec7ae03b1396b91b
+Frame No. 039:
+ * input:  d8a78b25e37a0022dd8a46dc68a0351bad391bde2046e56dd8dc96c038e396d89b
+ * output: d8a78b25e37a0022dd8a46dc68a0351bad391bde2046e56dd8dc96c038e396d89b
+Frame No. 040:
+ * input:  d8a88c255ab6e038e38e48dbde8038ad8dc8db8ec0376372b564b44038e49234dc
+ * output: d8a88c255ab6e038e38e48dbde8038ad8dc8db8ec0376372b564b44038e49234dc
+Frame No. 041:
+ * input:  d9708ce6a39ce049646646a2c1a0272496b29a66c037db562863ace0795b55b2e3
+ * output: d9708ce6a39ce049646646a2c1a0272496b29a66c037db562863ace0795b55b2e3
+Frame No. 042:
+ * input:  d8ee9bea5ae4003ae371b713eae05adc91995a5ea064dcc9571e786026ed51c52c
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