Feat: Support custom playback speed

player/video/src/main/java/dev/jdtech/jellyfin/dialogs/SpeedSelectionCustomSpeedDialogFragment.kt

@@ -0,0 +1,97 @@
+package dev.jdtech.jellyfin.dialogs
+
+import android.app.Dialog
+import android.os.Bundle
+import android.view.Gravity
+import android.widget.LinearLayout
+import android.widget.SeekBar
+import android.widget.TextView
+import androidx.fragment.app.DialogFragment
+import com.google.android.material.dialog.MaterialAlertDialogBuilder
+import dev.jdtech.jellyfin.player.video.R
+import kotlin.math.exp
+import kotlin.math.ln
+
+class SpeedSelectionCustomSpeedDialogFragment(
+    private val speedSelectionDialog: SpeedSelectionDialogFragment,
+    private val currentSpeed: Float,
+) : DialogFragment() {
+
+    /**
+     * Define the key values for the speed selection slide bar. Chosen for the logarithmic scaling.
+     */
+    private object SeekBarConstants {
+        private const val MAX_SPEED = 4.01f
+        private const val MIN_SPEED = 1 / 4f
+        const val NORMALIZATION = 2000
+        val MAX = (NORMALIZATION * ln(MAX_SPEED)).toInt()
+        val MIN = (NORMALIZATION * ln(MIN_SPEED)).toInt()
+    }
+
+    override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
+        return activity?.let { activity ->
+
+            val speedText = TextView(activity.baseContext)
+            speedText.text = createLabel(currentSpeed)
+            speedText.gravity = Gravity.CENTER
+
+            val seekBar = SeekBar(activity.baseContext)
+            seekBar.min = SeekBarConstants.MIN
+            seekBar.max = SeekBarConstants.MAX
+            seekBar.progress = speedToSeekBarValue(currentSpeed)
+
+            val listener = object : SeekBar.OnSeekBarChangeListener {
+
+                override fun onProgressChanged(seekBar: SeekBar?, progress: Int, fromUser: Boolean) {
+                    speedText.text = createLabel(seekBarValueToSpeed(seekBar?.progress ?: 0))
+                }
+
+                override fun onStartTrackingTouch(seekBar: SeekBar?) {} // NO-OP
+
+                override fun onStopTrackingTouch(seekBar: SeekBar?) {} // NO-OP
+            }
+            seekBar.setOnSeekBarChangeListener(listener)
+
+            val container = LinearLayout(activity.baseContext)
+            container.orientation = LinearLayout.VERTICAL
+            container.addView(speedText)
+            container.addView(seekBar)
+
+            MaterialAlertDialogBuilder(activity)
+                .setTitle(R.string.custom_playback_speed)
+                .setView(container)
+                .setPositiveButton(R.string.custom_playback_speed_confirm_button_label) { dialog, _ ->
+                    speedSelectionDialog.setCustomSpeed(seekBarValueToSpeed(seekBar.progress))
+                    dialog.dismiss()
+                }
+                .create()
+        } ?: throw IllegalStateException("Activity cannot be null")
+    }
+
+    /**
+     * Scale the integer value from the SeekBar to the associated playback speed multiplier.
+     * Uses a logarithmic scale so that X speed and 1/X speed are equidistant from 1x speed.
+     * Discards precision beyond 2 decimal places.
+     * Inverted by [speedToSeekBarValue].
+     */
+    private fun seekBarValueToSpeed(int: Int): Float {
+        val preciseSpeed = exp((int.toFloat() / SeekBarConstants.NORMALIZATION))
+        return ((100 * preciseSpeed).toInt() / 100f)
+    }
+
+    /**
+     * Scale a float playback speed multiplier to the associated progress value for the SeekBar.
+     * Uses a logarithmic scale so that X speed and 1/X speed are equidistant from 1x speed.
+     * Inverted by [seekBarValueToSpeed].
+     */
+    private fun speedToSeekBarValue(float: Float): Int {
+        return (SeekBarConstants.NORMALIZATION * ln(float)).toInt()
+    }
+
+    /**
+     * Create a formatted string for a label describing the selected playback speed multiplier.
+     */
+    private fun createLabel(float: Float): String {
+        return "%.2fx".format(float)
+    }
+}

player/video/src/main/java/dev/jdtech/jellyfin/dialogs/SpeedSelectionDialogFragment.kt

@@ -1,6 +1,7 @@
 package dev.jdtech.jellyfin.dialogs
 
 import android.app.Dialog
+import android.icu.text.DecimalFormat
 import android.os.Bundle
 import androidx.core.view.WindowCompat
 import androidx.core.view.WindowInsetsCompat
@@ -9,14 +10,28 @@ import androidx.fragment.app.DialogFragment
 import com.google.android.material.dialog.MaterialAlertDialogBuilder
 import dev.jdtech.jellyfin.player.video.R
 import dev.jdtech.jellyfin.viewmodels.PlayerActivityViewModel
-import java.lang.IllegalStateException
 
 class SpeedSelectionDialogFragment(
     private val viewModel: PlayerActivityViewModel,
 ) : DialogFragment() {
+
+    private companion object {
+        val PLAYBACK_SPEED_FORMAT = DecimalFormat("0.##x")
+    }
+
     override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
-        val speedTexts = listOf("0.5x", "0.75x", "1x", "1.25x", "1.5x", "1.75x", "2x")
-        val speedNumbers = listOf(0.5f, 0.75f, 1f, 1.25f, 1.5f, 1.75f, 2f)
+        val customLabel = getString(R.string.custom_playback_speed_label)
+        val currentSpeed = viewModel.playbackSpeed
+
+        val speedNumbers = mutableListOf(0.5f, 0.75f, 1f, 1.25f, 1.5f, 1.75f, 2f)
+        val speedTexts = speedNumbers.map(PLAYBACK_SPEED_FORMAT::format).toMutableList()
+
+        if (currentSpeed !in speedNumbers) {
+            speedTexts.add("$customLabel: ${PLAYBACK_SPEED_FORMAT.format(currentSpeed)}")
+            speedNumbers.add(currentSpeed)
+        } else {
+            speedTexts.add(customLabel)
+        }
 
         return activity?.let { activity ->
             val builder = MaterialAlertDialogBuilder(activity)
@@ -25,9 +40,13 @@ class SpeedSelectionDialogFragment(
                     speedTexts.toTypedArray(),
                     speedNumbers.indexOf(viewModel.playbackSpeed),
                 ) { dialog, which ->
-                    viewModel.selectSpeed(
-                        speedNumbers[which],
-                    )
+                    if (speedTexts[which].startsWith(customLabel)) {
+                        // Use a secondary dialog to determine the speed to set.
+                        SpeedSelectionCustomSpeedDialogFragment(this, currentSpeed)
+                            .show(activity.supportFragmentManager, "customSpeedSelection")
+                    } else {
+                        setCustomSpeed(speedNumbers[which])
+                    }
                     dialog.dismiss()
                 }
             builder.create()
@@ -44,4 +63,8 @@ class SpeedSelectionDialogFragment(
             }
         }
     }
+
+    fun setCustomSpeed(speed: Float) {
+        viewModel.selectSpeed(speed)
+    }
 }

player/video/src/main/res/values/strings.xml

@@ -2,6 +2,10 @@
     <string name="select_audio_track">Select audio track</string>
     <string name="select_subtile_track">Select subtitle track</string>
     <string name="select_playback_speed">Select playback speed</string>
+    <!--TODO: Add translations for custom playback speed strings.-->
+    <string name="custom_playback_speed">Playback speed</string>
+    <string name="custom_playback_speed_label">Custom</string>
+    <string name="custom_playback_speed_confirm_button_label">Set</string>
     <string name="select_a_version">"Select a version"</string>
     <string name="external">External</string>
     <string name="none">None</string>