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      1 /*
      2  * Copyright (C) 2015 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_NDEBUG 0
     18 #define LOG_TAG "FrameDropper"
     19 #include <utils/Log.h>
     20 
     21 #include "FrameDropper.h"
     22 
     23 #include <media/stagefright/foundation/ADebug.h>
     24 
     25 namespace android {
     26 
     27 static const int64_t kMaxJitterUs = 2000;
     28 
     29 FrameDropper::FrameDropper()
     30     : mDesiredMinTimeUs(-1),
     31       mMinIntervalUs(0) {
     32 }
     33 
     34 FrameDropper::~FrameDropper() {
     35 }
     36 
     37 status_t FrameDropper::setMaxFrameRate(float maxFrameRate) {
     38     if (maxFrameRate <= 0) {
     39         ALOGE("framerate should be positive but got %f.", maxFrameRate);
     40         return BAD_VALUE;
     41     }
     42     mMinIntervalUs = (int64_t) (1000000.0f / maxFrameRate);
     43     return OK;
     44 }
     45 
     46 bool FrameDropper::shouldDrop(int64_t timeUs) {
     47     if (mMinIntervalUs <= 0) {
     48         return false;
     49     }
     50 
     51     if (mDesiredMinTimeUs < 0) {
     52         mDesiredMinTimeUs = timeUs + mMinIntervalUs;
     53         ALOGV("first frame %lld, next desired frame %lld",
     54                 (long long)timeUs, (long long)mDesiredMinTimeUs);
     55         return false;
     56     }
     57 
     58     if (timeUs < (mDesiredMinTimeUs - kMaxJitterUs)) {
     59         ALOGV("drop frame %lld, desired frame %lld, diff %lld",
     60                 (long long)timeUs, (long long)mDesiredMinTimeUs,
     61                 (long long)(mDesiredMinTimeUs - timeUs));
     62         return true;
     63     }
     64 
     65     int64_t n = (timeUs - mDesiredMinTimeUs + kMaxJitterUs) / mMinIntervalUs;
     66     mDesiredMinTimeUs += (n + 1) * mMinIntervalUs;
     67     ALOGV("keep frame %lld, next desired frame %lld, diff %lld",
     68             (long long)timeUs, (long long)mDesiredMinTimeUs,
     69             (long long)(mDesiredMinTimeUs - timeUs));
     70     return false;
     71 }
     72 
     73 }  // namespace android
     74