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Implement Sonic method to get input frame count from output frame count

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The static method can estimate the number of input frames needed to get
a given number of output frames with a given Sonic configuration.

This CL is prework to remove the dependency of
`SpeedChangingAudioProcessor#getMediaDurationUs()` on non-static output
based heuristics and simplify `SpeedChangingAudioProcessor`.

PiperOrigin-RevId: 711446999
This commit is contained in:
ivanbuper 2025-01-02 09:33:30 -08:00 committed by Copybara-Service
parent 01c51d8475
commit 682889f91d
2 changed files with 180 additions and 2 deletions
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63
libraries/common/src/main/java/androidx/media3/common/audio/Sonic.java
View File

@ -36,6 +36,9 @@ import java.util.Arrays;
private static final int AMDF_FREQUENCY = 4000;
private static final int BYTES_PER_SAMPLE = 2;
private static final float MINIMUM_SPEEDUP_RATE = 1.00001f;
private static final float MINIMUM_SLOWDOWN_RATE = 0.99999f;
private final int inputSampleRateHz;
private final int channelCount;
private final float speed;
@ -91,7 +94,7 @@ import java.util.Arrays;
BigDecimal length = BigDecimal.valueOf(inputFrameCount);
BigDecimal framesAfterTimeStretching;
if (speedRate > 1.00001 || speedRate < 0.99999) {
if (speedRate > MINIMUM_SPEEDUP_RATE || speedRate < MINIMUM_SLOWDOWN_RATE) {
framesAfterTimeStretching =
length.divide(BigDecimal.valueOf(speedRate), RoundingMode.HALF_EVEN);
} else {
@ -143,6 +146,62 @@ import java.util.Arrays;
return accumulatedError.longValueExact();
}
/**
* Returns the number of input frames required for Sonic to produce the given number of output
* frames under the specified parameters.
*
* <p>This method is the inverse of {@link #getExpectedFrameCountAfterProcessorApplied}.
*
* @param inputSampleRateHz Input sample rate in Hertz.
* @param outputSampleRateHz Output sample rate in Hertz.
* @param speed Speed rate.
* @param pitch Pitch rate.
* @param outputFrameCount Number of output frames to calculate the required input frame count of.
*/
/* package */ static long getExpectedInputFrameCountForOutputFrameCount(
int inputSampleRateHz,
int outputSampleRateHz,
float speed,
float pitch,
long outputFrameCount) {
float resamplingRate = (float) inputSampleRateHz / outputSampleRateHz;
resamplingRate *= pitch;
BigDecimal bigResamplingRate = new BigDecimal(String.valueOf(resamplingRate));
long framesBeforeResampling =
getFrameCountBeforeResamplingForOutputCount(
BigDecimal.valueOf(inputSampleRateHz),
bigResamplingRate,
BigDecimal.valueOf(outputFrameCount));
double speedRate = speed / pitch;
if (speedRate > MINIMUM_SPEEDUP_RATE || speedRate < MINIMUM_SLOWDOWN_RATE) {
return BigDecimal.valueOf(framesBeforeResampling)
.multiply(BigDecimal.valueOf(speedRate))
.setScale(0, RoundingMode.FLOOR)
.longValueExact();
} else {
// If speed is almost 1, then just copy the buffers without modifying them.
return framesBeforeResampling;
}
}
/**
* Returns the expected input frame count prior to resampling with Sonic.
*
* <p>See {@link #getExpectedFrameCountAfterProcessorApplied} for more information.
*
* @param sampleRate Input sample rate of {@link Sonic} instance.
* @param resamplingRate Resampling rate given by {@code (inputSampleRate / outputSampleRate) *
* pitch}.
* @param outputLength Length of output in frames.
*/
private static long getFrameCountBeforeResamplingForOutputCount(
BigDecimal sampleRate, BigDecimal resamplingRate, BigDecimal outputLength) {
BigDecimal denominator = sampleRate.divide(resamplingRate, /* scale */ 0, RoundingMode.FLOOR);
BigDecimal numerator = sampleRate.multiply(outputLength);
return numerator.divide(denominator, /* scale */ 0, RoundingMode.FLOOR).longValueExact();
}
/**
* Creates a new Sonic audio stream processor.
*
@ -599,7 +658,7 @@ import java.util.Arrays;
int originalOutputFrameCount = outputFrameCount;
double s = speed / pitch;
float r = rate * pitch;
if (s > 1.00001 || s < 0.99999) {
if (s > MINIMUM_SPEEDUP_RATE || s < MINIMUM_SLOWDOWN_RATE) {
changeSpeed(s);
} else {
copyToOutput(inputBuffer, 0, inputFrameCount);

119
libraries/common/src/test/java/androidx/media3/common/audio/SonicTest.java
View File

@ -17,6 +17,7 @@ package androidx.media3.common.audio;
import static androidx.media3.common.audio.Sonic.calculateAccumulatedTruncationErrorForResampling;
import static androidx.media3.common.audio.Sonic.getExpectedFrameCountAfterProcessorApplied;
import static androidx.media3.common.audio.Sonic.getExpectedInputFrameCountForOutputFrameCount;
import static com.google.common.truth.Truth.assertThat;
import androidx.test.ext.junit.runners.AndroidJUnit4;
@ -260,4 +261,122 @@ public class SonicTest {
// (All calculations are done on BigDecimal rounded to 20 decimal places, unless indicated).
assertThat(error).isEqualTo(305);
}
@Test
public void getExpectedInputFrameCountForOutputFrameCount_fasterSpeed_returnsExpectedCount() {
long inputSamples =
getExpectedInputFrameCountForOutputFrameCount(
/* inputSampleRateHz= */ 48_000,
/* outputSampleRateHz= */ 48_000,
/* speed= */ 5,
/* pitch= */ 1,
/* outputFrameCount= */ 20);
assertThat(inputSamples).isEqualTo(100);
}
@Test
public void
getExpectedInputFrameCountForOutputFrameCount_fasterSpeedAndPitch_returnsExpectedCount() {
long inputSamples =
getExpectedInputFrameCountForOutputFrameCount(
/* inputSampleRateHz= */ 48_000,
/* outputSampleRateHz= */ 48_000,
/* speed= */ 5,
/* pitch= */ 5,
/* outputFrameCount= */ 20);
assertThat(inputSamples).isEqualTo(100);
}
@Test
public void getExpectedInputFrameCountForOutputFrameCount_higherPitch_returnsExpectedCount() {
long inputSamples =
getExpectedInputFrameCountForOutputFrameCount(
/* inputSampleRateHz= */ 48_000,
/* outputSampleRateHz= */ 48_000,
/* speed= */ 1,
/* pitch= */ 5,
/* outputFrameCount= */ 20);
assertThat(inputSamples).isEqualTo(20);
}
@Test
public void getExpectedInputFrameCountForOutputFrameCount_slowerSpeed_returnsExpectedCount() {
long inputSamples =
getExpectedInputFrameCountForOutputFrameCount(
/* inputSampleRateHz= */ 48_000,
/* outputSampleRateHz= */ 48_000,
/* speed= */ 0.25f,
/* pitch= */ 1,
/* outputFrameCount= */ 100);
assertThat(inputSamples).isEqualTo(25);
}
@Test
public void
getExpectedInputFrameCountForOutputFrameCount_slowerSpeedAndPitch_returnsExpectedCount() {
long inputSamples =
getExpectedInputFrameCountForOutputFrameCount(
/* inputSampleRateHz= */ 48_000,
/* outputSampleRateHz= */ 48_000,
/* speed= */ 0.25f,
/* pitch= */ 0.25f,
/* outputFrameCount= */ 100);
assertThat(inputSamples).isEqualTo(25);
}
@Test
public void getExpectedInputFrameCountForOutputFrameCount_lowerPitch_returnsExpectedCount() {
long inputSamples =
getExpectedInputFrameCountForOutputFrameCount(
/* inputSampleRateHz= */ 48_000,
/* outputSampleRateHz= */ 48_000,
/* speed= */ 1,
/* pitch= */ 0.75f,
/* outputFrameCount= */ 100);
assertThat(inputSamples).isEqualTo(100);
}
@Test
public void
getExpectedInputFrameCountForOutputFrameCount_differentSamplingRates_returnsExpectedCount() {
long inputSamples =
getExpectedInputFrameCountForOutputFrameCount(
/* inputSampleRateHz= */ 48_000,
/* outputSampleRateHz= */ 96_000,
/* speed= */ 1,
/* pitch= */ 1,
/* outputFrameCount= */ 100);
assertThat(inputSamples).isEqualTo(50);
}
@Test
public void
getExpectedInputFrameCountForOutputFrameCount_differentPitchSpeedAndSamplingRates_returnsExpectedCount() {
long inputSamples =
getExpectedInputFrameCountForOutputFrameCount(
/* inputSampleRateHz= */ 48_000,
/* outputSampleRateHz= */ 96_000,
/* speed= */ 5,
/* pitch= */ 2,
/* outputFrameCount= */ 40);
assertThat(inputSamples).isEqualTo(100);
}
@Test
public void
getExpectedInputFrameCountForOutputFrameCount_withPeriodicResamplingRate_adjustsForTruncationError() {
float resamplingRate = 0.33f;
long outputLength = 81_521_212;
long truncationError = 305;
long inputSamples =
getExpectedInputFrameCountForOutputFrameCount(
/* inputSampleRateHz= */ 48_000,
/* outputSampleRateHz= */ 48_000,
/* speed= */ resamplingRate,
/* pitch= */ resamplingRate,
/* outputFrameCount= */ outputLength - truncationError);
assertThat(inputSamples).isEqualTo(26_902_000);
}
}