--- title: "Sound Extraction" canonical_url: "https://www.nutrient.io/guides/android/samples/sound-extraction-kotlin/" md_url: "https://www.nutrient.io/guides/android/samples/sound-extraction-kotlin.md" last_updated: "2026-05-15T19:10:04.916Z" description: "Add a sound annotation and extract the audio data to a .wav file." --- # Sound Extraction Add a sound annotation and extract the audio data to a.wav file. [Get Started](https://www.nutrient.io/sdk/android/getting-started.md) [All Samples](https://www.nutrient.io/guides/android/samples.md) [Download](https://www.nutrient.io/guides/android/downloads.md) [Launch Demo](https://www.nutrient.io/demo/) --- ```kotlin /* * Copyright © 2020-2026 PSPDFKit GmbH. All rights reserved. * * The PSPDFKit Sample applications are licensed with a modified BSD license. * Please see License for details. This notice may not be removed from this file. */ package com.pspdfkit.catalog.examples.kotlin import android.annotation.SuppressLint import android.content.Context import android.graphics.RectF import android.net.Uri import android.view.Menu import android.view.MenuItem import android.widget.Toast import androidx.activity.viewModels import androidx.annotation.UiThread import androidx.core.net.toUri import com.pspdfkit.annotations.SoundAnnotation import com.pspdfkit.annotations.sound.AudioExtractor import com.pspdfkit.annotations.sound.WavWriter import com.pspdfkit.catalog.R import com.pspdfkit.catalog.SdkExample import com.pspdfkit.catalog.tasks.ExtractAssetTask import com.pspdfkit.configuration.activity.PdfActivityConfiguration import com.pspdfkit.document.PdfDocument import com.pspdfkit.preferences.PSPDFKitPreferences import com.pspdfkit.ui.PdfActivity import com.pspdfkit.ui.PdfActivityIntentBuilder import com.pspdfkit.ui.special_mode.controller.AnnotationTool import kotlinx.coroutines.runBlocking import java.io.File import java.io.FileOutputStream import java.io.IOException /** * An example on how to create a sound annotation programmatically and extract the audio data from it. */ class SoundAnnotationDataExtractionExample(context: Context) : SdkExample(context, R.string.soundAnnotationDataExtractionTitle, R.string.soundAnnotationDataExtractionDescription) { override fun launchExample(context: Context, configuration: PdfActivityConfiguration.Builder) { // Turn off saving, so we have the clean original document every time the example is launched. configuration.autosaveEnabled(false) configuration.enabledAnnotationTools( listOf( AnnotationTool.SOUND, ), ) // The annotation creator written into newly created annotations. If not set, or set to `null` // a dialog will normally be shown when creating an annotation, asking the user to enter a name. // We are going to skip this part and set it as "John Doe" only if it was not yet set. if (!PSPDFKitPreferences.get(context).isAnnotationCreatorSet) { PSPDFKitPreferences.get(context).setAnnotationCreator("John Doe") } // Extract the document from the assets. The launched activity will add annotations to that document. ExtractAssetTask.extract(WELCOME_DOC, title, context) { documentFile -> val intent = PdfActivityIntentBuilder.fromUri(context, Uri.fromFile(documentFile)).configuration(configuration.build()).activityClass(SoundAnnotationDataExtractionActivity::class).build() context.startActivity(intent) } } } /** * This activity creates a sound annotation when the document is loaded. * It also adds a custom menu item to the toolbar that extracts the sound data from the annotation and saves it to a.wav file. */ class SoundAnnotationDataExtractionActivity : PdfActivity() { private val viewModel: AnnotationCreationViewModel by viewModels() @UiThread override fun onDocumentLoaded(document: PdfDocument) { viewModel.createObjects { createSoundAnnotation() } } override fun onCreateOptionsMenu(menu: Menu): Boolean { super.onCreateOptionsMenu(menu) menu.add(0, MENU_ID, 0, "Extract sound.wav") return true } override fun onOptionsItemSelected(item: MenuItem): Boolean = if (item.itemId == MENU_ID) { menuItemClicked() true } else { super.onOptionsItemSelected(item) } private fun menuItemClicked() { extractSoundData() } @SuppressLint("CheckResult") private fun createSoundAnnotation() { try { // Extract first audio track from sample in assets. // Audio extractor supports decoding audio tracks from all media formats that are supported by Android's `MediaExtractor`. val audioExtractor = AudioExtractor(this, "file:///android_asset/media/audioLoop.wav".toUri()) audioExtractor.selectAudioTrack(0) audioExtractor.extractAudioTrackAsync().subscribe { embeddedAudioSource -> // Create new sound annotation from the extracted audio track. val soundAnnotation = SoundAnnotation(0, RectF(580f, 700f, 600f, 685f), embeddedAudioSource) requirePdfFragment().addAnnotationToPage(soundAnnotation, false) } } catch (e: IOException) { // Handle possible IOException, thrown when the Uri does not point to correct file/asset. } } private fun extractSoundData() { val annotations = runBlocking { document?.annotationProvider?.getAnnotations(0) }?: return val soundAnnotation = annotations[0] as SoundAnnotation val outputFile = File.createTempFile("tmp_", "sound.wav") WavWriter.forAnnotation(soundAnnotation).writeToStream(FileOutputStream(outputFile)) Toast.makeText(this, "Wav file saved to: ${outputFile.path}", Toast.LENGTH_SHORT).show() println("Wav: ${outputFile.path}") } companion object { private const val MENU_ID = 1 } } ``` This code sample is an example that illustrates how to use our SDK. 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