TestAudioClock.cpp

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/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "AudioStream.h"

#include "gtest/gtest.h"

using namespace mozilla;

// AudioClock maps the audio engine's raw frame counter -- an absolute,

// monotonically increasing frame position -- to a media-time position in

// microseconds. Rebase(rawCount) re-zeroes that mapping so the given raw count

// corresponds to media position 0: it sets the base offset to rawCount, the

// base position to 0, and clears the serviced-frame history. The argument is a

// frame count, not a time: a stream reused across a seek keeps its counter

// climbing, so the clock is re-zeroed at the current count, while the seek

// target itself is applied separately by the sink. At 48000 Hz one second is

// exactly 48000 frames, so the expected microsecond values below are exact.

// Rebase at a non-zero count: after servicing frames, Rebase(currentRawCount)

// makes that count read as position 0, and later servicing advances from there.

TEST(AudioClock, RebaseOnReset)

  const uint32_t rate = 48000;

  AudioClock clock(rate);

  clock.UpdateFrameHistory(rate, 0, false);

  EXPECT_EQ(clock.GetPosition(rate), 1000000)

      << "one second of serviced frames reads as 1.0 s";

  clock.Rebase(rate);

  EXPECT_EQ(clock.GetPosition(rate), 0)

      << "rebasing at the current count makes that count read as 0";

  clock.UpdateFrameHistory(rate / 2, 0, false);

  EXPECT_EQ(clock.GetPosition(rate + rate / 2), 500000)

      << "servicing half a second more reads as 0.5 s from the rebased base";

  clock.Rebase(rate + rate / 2);

  EXPECT_EQ(clock.GetPosition(rate + rate / 2), 0)

      << "a second rebase re-zeroes again at the current count";

// Rebase at zero: the boundary case (RebaseLive falls back to Rebase(0) when

// the engine position reads 0). It clears any accumulated history so the

// current count reads as 0, and later servicing accumulates from there.

TEST(AudioClock, RebaseToZero)

  const uint32_t rate = 48000;

  AudioClock clock(rate);

  clock.UpdateFrameHistory(rate, 0, false);

  EXPECT_EQ(clock.GetPosition(rate), 1000000)

      << "one second of serviced frames reads as 1.0 s";

  clock.Rebase(0);

  EXPECT_EQ(clock.GetPosition(0), 0)

      << "Rebase(0) clears accumulated history so the count reads as 0";

  clock.UpdateFrameHistory(rate, 0, false);

  EXPECT_EQ(clock.GetPosition(rate), 1000000)

      << "later servicing accumulates from the rebased zero";