76 lines
2.4 KiB
C++
76 lines
2.4 KiB
C++
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "packager/media/base/audio_timestamp_helper.h"
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#include "packager/base/logging.h"
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#include "packager/media/base/timestamp.h"
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namespace shaka {
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namespace media {
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AudioTimestampHelper::AudioTimestampHelper(uint32_t timescale,
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uint32_t samples_per_second)
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: base_timestamp_(kNoTimestamp), frame_count_(0) {
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DCHECK_GT(samples_per_second, 0u);
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double fps = samples_per_second;
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ticks_per_frame_ = timescale / fps;
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}
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void AudioTimestampHelper::SetBaseTimestamp(int64_t base_timestamp) {
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base_timestamp_ = base_timestamp;
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frame_count_ = 0;
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}
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int64_t AudioTimestampHelper::base_timestamp() const {
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return base_timestamp_;
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}
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void AudioTimestampHelper::AddFrames(int64_t frame_count) {
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DCHECK_GE(frame_count, 0);
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DCHECK(base_timestamp_ != kNoTimestamp);
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frame_count_ += frame_count;
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}
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int64_t AudioTimestampHelper::GetTimestamp() const {
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return ComputeTimestamp(frame_count_);
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}
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int64_t AudioTimestampHelper::GetFrameDuration(int64_t frame_count) const {
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DCHECK_GE(frame_count, 0);
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int64_t end_timestamp = ComputeTimestamp(frame_count_ + frame_count);
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return end_timestamp - GetTimestamp();
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}
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int64_t AudioTimestampHelper::GetFramesToTarget(int64_t target) const {
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DCHECK(base_timestamp_ != kNoTimestamp);
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DCHECK(target >= base_timestamp_);
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int64_t delta_in_ticks = (target - GetTimestamp());
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if (delta_in_ticks == 0)
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return 0;
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// Compute a timestamp relative to |base_timestamp_| since timestamps
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// created from |frame_count_| are computed relative to this base.
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// This ensures that the time to frame computation here is the proper inverse
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// of the frame to time computation in ComputeTimestamp().
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int64_t delta_from_base = target - base_timestamp_;
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// Compute frame count for the time delta. This computation rounds to
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// the nearest whole number of frames.
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double threshold = ticks_per_frame_ / 2;
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int64_t target_frame_count = (delta_from_base + threshold) / ticks_per_frame_;
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return target_frame_count - frame_count_;
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}
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int64_t AudioTimestampHelper::ComputeTimestamp(int64_t frame_count) const {
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DCHECK_GE(frame_count, 0);
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DCHECK(base_timestamp_ != kNoTimestamp);
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double frames_ticks = ticks_per_frame_ * frame_count;
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return base_timestamp_ + frames_ticks;
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}
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} // namespace media
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} // namespace shaka
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