| henrike@webrtc.org | 0e118e7 | 2013-07-10 00:45:36 +0000 | [diff] [blame] | 1 | /* |
| 2 | * libjingle |
| 3 | * Copyright 2011, Google Inc. |
| 4 | * |
| 5 | * Redistribution and use in source and binary forms, with or without |
| 6 | * modification, are permitted provided that the following conditions are met: |
| 7 | * |
| 8 | * 1. Redistributions of source code must retain the above copyright notice, |
| 9 | * this list of conditions and the following disclaimer. |
| 10 | * 2. Redistributions in binary form must reproduce the above copyright notice, |
| 11 | * this list of conditions and the following disclaimer in the documentation |
| 12 | * and/or other materials provided with the distribution. |
| 13 | * 3. The name of the author may not be used to endorse or promote products |
| 14 | * derived from this software without specific prior written permission. |
| 15 | * |
| 16 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED |
| 17 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF |
| 18 | * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO |
| 19 | * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 20 | * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| 21 | * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; |
| 22 | * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
| 23 | * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR |
| 24 | * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF |
| 25 | * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 26 | */ |
| 27 | |
| 28 | #ifndef TALK_BASE_BANDWIDTHSMOOTHER_H_ |
| 29 | #define TALK_BASE_BANDWIDTHSMOOTHER_H_ |
| 30 | |
| 31 | #include "talk/base/rollingaccumulator.h" |
| 32 | #include "talk/base/timeutils.h" |
| 33 | |
| 34 | namespace talk_base { |
| 35 | |
| 36 | // The purpose of BandwidthSmoother is to smooth out bandwidth |
| 37 | // estimations so that 'trstate' messages can be triggered when we |
| 38 | // are "sure" there is sufficient bandwidth. To avoid frequent fluctuations, |
| 39 | // we take a slightly pessimistic view of our bandwidth. We only increase |
| 40 | // our estimation when we have sampled bandwidth measurements of values |
| 41 | // at least as large as the current estimation * percent_increase |
| 42 | // for at least time_between_increase time. If a sampled bandwidth |
| 43 | // is less than our current estimation we immediately decrease our estimation |
| 44 | // to that sampled value. |
| 45 | // We retain the initial bandwidth guess as our current bandwidth estimation |
| 46 | // until we have received (min_sample_count_percent * samples_count_to_average) |
| 47 | // number of samples. Min_sample_count_percent must be in range [0, 1]. |
| 48 | class BandwidthSmoother { |
| 49 | public: |
| 50 | BandwidthSmoother(int initial_bandwidth_guess, |
| 51 | uint32 time_between_increase, |
| 52 | double percent_increase, |
| 53 | size_t samples_count_to_average, |
| 54 | double min_sample_count_percent); |
| 55 | |
| 56 | // Samples a new bandwidth measurement. |
| 57 | // bandwidth is expected to be non-negative. |
| 58 | // returns true if the bandwidth estimation changed |
| 59 | bool Sample(uint32 sample_time, int bandwidth); |
| 60 | |
| 61 | int get_bandwidth_estimation() const { |
| 62 | return bandwidth_estimation_; |
| 63 | } |
| 64 | |
| 65 | private: |
| 66 | uint32 time_between_increase_; |
| 67 | double percent_increase_; |
| 68 | uint32 time_at_last_change_; |
| 69 | int bandwidth_estimation_; |
| 70 | RollingAccumulator<int> accumulator_; |
| 71 | double min_sample_count_percent_; |
| 72 | }; |
| 73 | |
| 74 | } // namespace talk_base |
| 75 | |
| 76 | #endif // TALK_BASE_BANDWIDTHSMOOTHER_H_ |