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< li class = "navelem" > < a class = "el" href = "../../dir_39dc0668bd5a501998f94e8b4e546c71.html" > media< / a > < / li > < li class = "navelem" > < a class = "el" href = "../../dir_c6ada2450b25ab5438a4dba6c9b890af.html" > base< / a > < / li > < / ul >
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< div class = "title" > audio_timestamp_helper.cc< / div > < / div >
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< div class = "fragment" > < div class = "line" > < a name = "l00001" > < / a > < span class = "lineno" > 1< / span >   < span class = "comment" > // Copyright (c) 2012 The Chromium Authors. All rights reserved.< / span > < / div >
< div class = "line" > < a name = "l00002" > < / a > < span class = "lineno" > 2< / span >   < span class = "comment" > // Use of this source code is governed by a BSD-style license that can be< / span > < / div >
< div class = "line" > < a name = "l00003" > < / a > < span class = "lineno" > 3< / span >   < span class = "comment" > // found in the LICENSE file.< / span > < / div >
< div class = "line" > < a name = "l00004" > < / a > < span class = "lineno" > 4< / span >   < / div >
< div class = "line" > < a name = "l00005" > < / a > < span class = "lineno" > 5< / span >   < span class = "preprocessor" > #include " packager/media/base/audio_timestamp_helper.h" < / span > < / div >
< div class = "line" > < a name = "l00006" > < / a > < span class = "lineno" > 6< / span >   < / div >
< div class = "line" > < a name = "l00007" > < / a > < span class = "lineno" > 7< / span >   < span class = "preprocessor" > #include " packager/base/logging.h" < / span > < / div >
< div class = "line" > < a name = "l00008" > < / a > < span class = "lineno" > 8< / span >   < span class = "preprocessor" > #include " packager/media/base/timestamp.h" < / span > < / div >
< div class = "line" > < a name = "l00009" > < / a > < span class = "lineno" > 9< / span >   < / div >
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< div class = "line" > < a name = "l00010" > < / a > < span class = "lineno" > 10< / span >   < span class = "keyword" > namespace < / span > shaka {< / div >
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< div class = "line" > < a name = "l00011" > < / a > < span class = "lineno" > 11< / span >   < span class = "keyword" > namespace < / span > media {< / div >
< div class = "line" > < a name = "l00012" > < / a > < span class = "lineno" > 12< / span >   < / div >
< div class = "line" > < a name = "l00013" > < / a > < span class = "lineno" > 13< / span >   AudioTimestampHelper::AudioTimestampHelper(uint32_t timescale,< / div >
< div class = "line" > < a name = "l00014" > < / a > < span class = "lineno" > 14< / span >   uint32_t samples_per_second)< / div >
< div class = "line" > < a name = "l00015" > < / a > < span class = "lineno" > 15< / span >   : base_timestamp_(kNoTimestamp), frame_count_(0) {< / div >
< div class = "line" > < a name = "l00016" > < / a > < span class = "lineno" > 16< / span >   DCHECK_GT(samples_per_second, 0u);< / div >
< div class = "line" > < a name = "l00017" > < / a > < span class = "lineno" > 17< / span >   < span class = "keywordtype" > double< / span > fps = samples_per_second;< / div >
< div class = "line" > < a name = "l00018" > < / a > < span class = "lineno" > 18< / span >   ticks_per_frame_ = timescale / fps;< / div >
< div class = "line" > < a name = "l00019" > < / a > < span class = "lineno" > 19< / span >   }< / div >
< div class = "line" > < a name = "l00020" > < / a > < span class = "lineno" > 20< / span >   < / div >
< div class = "line" > < a name = "l00021" > < / a > < span class = "lineno" > 21< / span >   < span class = "keywordtype" > void< / span > AudioTimestampHelper::SetBaseTimestamp(int64_t base_timestamp) {< / div >
< div class = "line" > < a name = "l00022" > < / a > < span class = "lineno" > 22< / span >   base_timestamp_ = base_timestamp;< / div >
< div class = "line" > < a name = "l00023" > < / a > < span class = "lineno" > 23< / span >   frame_count_ = 0;< / div >
< div class = "line" > < a name = "l00024" > < / a > < span class = "lineno" > 24< / span >   }< / div >
< div class = "line" > < a name = "l00025" > < / a > < span class = "lineno" > 25< / span >   < / div >
< div class = "line" > < a name = "l00026" > < / a > < span class = "lineno" > 26< / span >   int64_t AudioTimestampHelper::base_timestamp()< span class = "keyword" > const < / span > {< / div >
< div class = "line" > < a name = "l00027" > < / a > < span class = "lineno" > 27< / span >   < span class = "keywordflow" > return< / span > base_timestamp_;< / div >
< div class = "line" > < a name = "l00028" > < / a > < span class = "lineno" > 28< / span >   }< / div >
< div class = "line" > < a name = "l00029" > < / a > < span class = "lineno" > 29< / span >   < / div >
< div class = "line" > < a name = "l00030" > < / a > < span class = "lineno" > 30< / span >   < span class = "keywordtype" > void< / span > AudioTimestampHelper::AddFrames(int64_t frame_count) {< / div >
< div class = "line" > < a name = "l00031" > < / a > < span class = "lineno" > 31< / span >   DCHECK_GE(frame_count, 0);< / div >
< div class = "line" > < a name = "l00032" > < / a > < span class = "lineno" > 32< / span >   DCHECK(base_timestamp_ != kNoTimestamp);< / div >
< div class = "line" > < a name = "l00033" > < / a > < span class = "lineno" > 33< / span >   frame_count_ += frame_count;< / div >
< div class = "line" > < a name = "l00034" > < / a > < span class = "lineno" > 34< / span >   }< / div >
< div class = "line" > < a name = "l00035" > < / a > < span class = "lineno" > 35< / span >   < / div >
< div class = "line" > < a name = "l00036" > < / a > < span class = "lineno" > 36< / span >   int64_t AudioTimestampHelper::GetTimestamp()< span class = "keyword" > const < / span > {< / div >
< div class = "line" > < a name = "l00037" > < / a > < span class = "lineno" > 37< / span >   < span class = "keywordflow" > return< / span > ComputeTimestamp(frame_count_);< / div >
< div class = "line" > < a name = "l00038" > < / a > < span class = "lineno" > 38< / span >   }< / div >
< div class = "line" > < a name = "l00039" > < / a > < span class = "lineno" > 39< / span >   < / div >
< div class = "line" > < a name = "l00040" > < / a > < span class = "lineno" > 40< / span >   int64_t AudioTimestampHelper::GetFrameDuration(int64_t frame_count)< span class = "keyword" > const < / span > {< / div >
< div class = "line" > < a name = "l00041" > < / a > < span class = "lineno" > 41< / span >   DCHECK_GE(frame_count, 0);< / div >
< div class = "line" > < a name = "l00042" > < / a > < span class = "lineno" > 42< / span >   int64_t end_timestamp = ComputeTimestamp(frame_count_ + frame_count);< / div >
< div class = "line" > < a name = "l00043" > < / a > < span class = "lineno" > 43< / span >   < span class = "keywordflow" > return< / span > end_timestamp - GetTimestamp();< / div >
< div class = "line" > < a name = "l00044" > < / a > < span class = "lineno" > 44< / span >   }< / div >
< div class = "line" > < a name = "l00045" > < / a > < span class = "lineno" > 45< / span >   < / div >
< div class = "line" > < a name = "l00046" > < / a > < span class = "lineno" > 46< / span >   int64_t AudioTimestampHelper::GetFramesToTarget(int64_t target)< span class = "keyword" > const < / span > {< / div >
< div class = "line" > < a name = "l00047" > < / a > < span class = "lineno" > 47< / span >   DCHECK(base_timestamp_ != kNoTimestamp);< / div >
< div class = "line" > < a name = "l00048" > < / a > < span class = "lineno" > 48< / span >   DCHECK(target > = base_timestamp_);< / div >
< div class = "line" > < a name = "l00049" > < / a > < span class = "lineno" > 49< / span >   < / div >
< div class = "line" > < a name = "l00050" > < / a > < span class = "lineno" > 50< / span >   int64_t delta_in_ticks = (target - GetTimestamp());< / div >
< div class = "line" > < a name = "l00051" > < / a > < span class = "lineno" > 51< / span >   < span class = "keywordflow" > if< / span > (delta_in_ticks == 0)< / div >
< div class = "line" > < a name = "l00052" > < / a > < span class = "lineno" > 52< / span >   < span class = "keywordflow" > return< / span > 0;< / div >
< div class = "line" > < a name = "l00053" > < / a > < span class = "lineno" > 53< / span >   < / div >
< div class = "line" > < a name = "l00054" > < / a > < span class = "lineno" > 54< / span >   < span class = "comment" > // Compute a timestamp relative to |base_timestamp_| since timestamps< / span > < / div >
< div class = "line" > < a name = "l00055" > < / a > < span class = "lineno" > 55< / span >   < span class = "comment" > // created from |frame_count_| are computed relative to this base.< / span > < / div >
< div class = "line" > < a name = "l00056" > < / a > < span class = "lineno" > 56< / span >   < span class = "comment" > // This ensures that the time to frame computation here is the proper inverse< / span > < / div >
< div class = "line" > < a name = "l00057" > < / a > < span class = "lineno" > 57< / span >   < span class = "comment" > // of the frame to time computation in ComputeTimestamp().< / span > < / div >
< div class = "line" > < a name = "l00058" > < / a > < span class = "lineno" > 58< / span >   int64_t delta_from_base = target - base_timestamp_;< / div >
< div class = "line" > < a name = "l00059" > < / a > < span class = "lineno" > 59< / span >   < / div >
< div class = "line" > < a name = "l00060" > < / a > < span class = "lineno" > 60< / span >   < span class = "comment" > // Compute frame count for the time delta. This computation rounds to< / span > < / div >
< div class = "line" > < a name = "l00061" > < / a > < span class = "lineno" > 61< / span >   < span class = "comment" > // the nearest whole number of frames.< / span > < / div >
< div class = "line" > < a name = "l00062" > < / a > < span class = "lineno" > 62< / span >   < span class = "keywordtype" > double< / span > threshold = ticks_per_frame_ / 2;< / div >
< div class = "line" > < a name = "l00063" > < / a > < span class = "lineno" > 63< / span >   int64_t target_frame_count = (delta_from_base + threshold) / ticks_per_frame_;< / div >
< div class = "line" > < a name = "l00064" > < / a > < span class = "lineno" > 64< / span >   < span class = "keywordflow" > return< / span > target_frame_count - frame_count_;< / div >
< div class = "line" > < a name = "l00065" > < / a > < span class = "lineno" > 65< / span >   }< / div >
< div class = "line" > < a name = "l00066" > < / a > < span class = "lineno" > 66< / span >   < / div >
< div class = "line" > < a name = "l00067" > < / a > < span class = "lineno" > 67< / span >   int64_t AudioTimestampHelper::ComputeTimestamp(int64_t frame_count)< span class = "keyword" > const < / span > {< / div >
< div class = "line" > < a name = "l00068" > < / a > < span class = "lineno" > 68< / span >   DCHECK_GE(frame_count, 0);< / div >
< div class = "line" > < a name = "l00069" > < / a > < span class = "lineno" > 69< / span >   DCHECK(base_timestamp_ != kNoTimestamp);< / div >
< div class = "line" > < a name = "l00070" > < / a > < span class = "lineno" > 70< / span >   < span class = "keywordtype" > double< / span > frames_ticks = ticks_per_frame_ * frame_count;< / div >
< div class = "line" > < a name = "l00071" > < / a > < span class = "lineno" > 71< / span >   < span class = "keywordflow" > return< / span > base_timestamp_ + frames_ticks;< / div >
< div class = "line" > < a name = "l00072" > < / a > < span class = "lineno" > 72< / span >   }< / div >
< div class = "line" > < a name = "l00073" > < / a > < span class = "lineno" > 73< / span >   < / div >
< div class = "line" > < a name = "l00074" > < / a > < span class = "lineno" > 74< / span >   } < span class = "comment" > // namespace media< / span > < / div >
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< div class = "line" > < a name = "l00075" > < / a > < span class = "lineno" > 75< / span >   } < span class = "comment" > // namespace shaka< / span > < / div >
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