1 /*
2 * Copyright (C) 2021 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #define LOG_TAG "JitterCalc"
18 #include <utils/Log.h>
19
20 #include "JitterCalculator.h"
21
22 #include <stdlib.h>
23
24 namespace android {
25
JitterCalc(int32_t clockRate)26 JitterCalc::JitterCalc(int32_t clockRate)
27 : mClockRate(clockRate) {
28 init(0, 0, 0, 0);
29 }
30
init(uint32_t rtpTime,int64_t arrivalTimeUs,int32_t base,int32_t inter)31 void JitterCalc::init(uint32_t rtpTime, int64_t arrivalTimeUs, int32_t base, int32_t inter) {
32 mFirstTimeStamp = rtpTime;
33 mLastTimeStamp = rtpTime;
34 mFirstArrivalTimeUs = arrivalTimeUs;
35 mLastArrivalTimeUs = arrivalTimeUs;
36
37 mBaseJitterUs = base;
38 mInterArrivalJitterUs = inter;
39 }
40
putBaseData(int64_t rtpTime,int64_t arrivalTimeUs)41 void JitterCalc::putBaseData(int64_t rtpTime, int64_t arrivalTimeUs) {
42 // A RTP time wraps around after UINT32_MAX. We must consider this case.
43 const int64_t UINT32_MSB = 0x80000000;
44 int64_t overflowMask = (mFirstTimeStamp & UINT32_MSB & ~rtpTime) << 1;
45 int64_t tempRtpTime = overflowMask | rtpTime;
46
47 // Base jitter implementation can be various
48 int64_t scheduledTimeUs = (tempRtpTime - (int64_t)mFirstTimeStamp) * 1000000ll / mClockRate;
49 int64_t elapsedTimeUs = arrivalTimeUs - mFirstArrivalTimeUs;
50 int64_t correctionTimeUs = elapsedTimeUs - scheduledTimeUs; // additional propagation delay;
51 mBaseJitterUs = (mBaseJitterUs * 15 + correctionTimeUs) / 16;
52 ALOGV("BaseJitterUs : %lld \t\t correctionTimeUs : %lld",
53 (long long)mBaseJitterUs, (long long)correctionTimeUs);
54 }
55
putInterArrivalData(int64_t rtpTime,int64_t arrivalTimeUs)56 void JitterCalc::putInterArrivalData(int64_t rtpTime, int64_t arrivalTimeUs) {
57 const int64_t UINT32_MSB = 0x80000000;
58 int64_t tempRtpTime = rtpTime;
59 int64_t tempLastTimeStamp = mLastTimeStamp;
60
61 // A RTP time wraps around after UINT32_MAX. We must consider this case.
62 int64_t overflowMask = (mLastTimeStamp ^ rtpTime) & UINT32_MSB;
63 tempRtpTime |= ((overflowMask & ~rtpTime) << 1);
64 tempLastTimeStamp |= ((overflowMask & ~mLastTimeStamp) << 1);
65
66 // 6.4.1 of RFC3550 defines this interarrival jitter value.
67 int64_t diffTimeStampUs = abs(tempRtpTime - tempLastTimeStamp) * 1000000ll / mClockRate;
68 int64_t diffArrivalUs = arrivalTimeUs - mLastArrivalTimeUs; // Can't be minus
69 ALOGV("diffTimeStampUs %lld \t\t diffArrivalUs %lld",
70 (long long)diffTimeStampUs, (long long)diffArrivalUs);
71
72 int64_t varianceUs = diffArrivalUs - diffTimeStampUs;
73 mInterArrivalJitterUs = (mInterArrivalJitterUs * 15 + abs(varianceUs)) / 16;
74
75 mLastTimeStamp = (uint32_t)rtpTime;
76 mLastArrivalTimeUs = arrivalTimeUs;
77 }
78
getBaseJitterMs()79 int32_t JitterCalc::getBaseJitterMs() {
80 return mBaseJitterUs / 1000;
81 }
82
getInterArrivalJitterMs()83 int32_t JitterCalc::getInterArrivalJitterMs() {
84 return mInterArrivalJitterUs / 1000;
85 }
86
87 } // namespace android
88
89