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fix: race condition in VideoFrameDecoder causing SIGSEGV and IllegalStateException
Serialize access to the cached MediaCodec decoder with a Mutex to prevent
concurrent access from multiple IO threads. Add error recovery so a broken
decoder is released and recreated on the next call.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
author
virtualintern
co-author
Claude Opus 4.6 (1M context)
date
(Apr 2, 2026, 5:03 PM +0300)
commit
1a0a549a
1a0a549a69d7215e11c1919c91122c2801542a5a
parent
3a1a0382
3a1a0382796c7e8ba405585f0331ca0bb5a4a743
+66
-48
+1
-1
posedetection/build.gradle.kts
+1
-1
posedetection/build.gradle.kts
···
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mavenPublishing {
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publishToMavenCentral(SonatypeHost.CENTRAL_PORTAL)
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coordinates("com.performancecoachlab.posedetection", "posedetection-compose", "4.9.0")
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coordinates("com.performancecoachlab.posedetection", "posedetection-compose", "4.9.2")
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pom {
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name.set("Pose Detection")
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posedetection/src/androidMain/kotlin/com/performancecoachlab/posedetection/recording/VideoUtils.android.kt
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posedetection/src/androidMain/kotlin/com/performancecoachlab/posedetection/recording/VideoUtils.android.kt
···
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import androidx.core.net.toUri
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import co.touchlab.kermit.Logger
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import kotlinx.coroutines.Dispatchers
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import kotlinx.coroutines.sync.Mutex
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import kotlinx.coroutines.sync.withLock
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import kotlinx.coroutines.withContext
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import kotlin.coroutines.cancellation.CancellationException
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/**
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* Sequential video decoder using MediaCodec. Opens the video once and decodes
···
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val timeoutUs = 10_000L
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val info = MediaCodec.BufferInfo()
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while (!outputEos) {
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// Feed input packets.
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if (!inputEos) {
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val inIdx = decoder.dequeueInputBuffer(0)
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if (inIdx >= 0) {
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val buf = decoder.getInputBuffer(inIdx)!!
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val size = ext.readSampleData(buf, 0)
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if (size < 0) {
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decoder.queueInputBuffer(
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inIdx, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM
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)
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inputEos = true
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} else {
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decoder.queueInputBuffer(inIdx, 0, size, ext.sampleTime, 0)
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ext.advance()
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try {
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while (!outputEos) {
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// Feed input packets.
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if (!inputEos) {
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val inIdx = decoder.dequeueInputBuffer(0)
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if (inIdx >= 0) {
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val buf = decoder.getInputBuffer(inIdx)!!
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val size = ext.readSampleData(buf, 0)
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if (size < 0) {
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decoder.queueInputBuffer(
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inIdx, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM
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)
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inputEos = true
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} else {
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decoder.queueInputBuffer(inIdx, 0, size, ext.sampleTime, 0)
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ext.advance()
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}
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}
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}
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}
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// Drain output.
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val outIdx = decoder.dequeueOutputBuffer(info, timeoutUs)
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if (outIdx >= 0) {
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val ptsMs = info.presentationTimeUs / 1000L
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// Drain output.
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val outIdx = decoder.dequeueOutputBuffer(info, timeoutUs)
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if (outIdx >= 0) {
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val ptsMs = info.presentationTimeUs / 1000L
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if (info.size > 0) {
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val image = decoder.getOutputImage(outIdx)
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if (image != null) {
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// Recycle previous bitmap to limit memory.
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if (lastPtsMs != ptsMs) {
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// Don't recycle if we'd lose the only copy.
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if (info.size > 0) {
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val image = decoder.getOutputImage(outIdx)
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if (image != null) {
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val raw = yuvImageToBitmap(image)
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image.close()
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lastBitmap = applyRotation(raw)
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lastPtsMs = ptsMs
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}
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val raw = yuvImageToBitmap(image)
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image.close()
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lastBitmap = applyRotation(raw)
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lastPtsMs = ptsMs
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}
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}
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val eos = info.flags and MediaCodec.BUFFER_FLAG_END_OF_STREAM != 0
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decoder.releaseOutputBuffer(outIdx, false)
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val eos = info.flags and MediaCodec.BUFFER_FLAG_END_OF_STREAM != 0
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decoder.releaseOutputBuffer(outIdx, false)
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if (eos) {
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outputEos = true
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return lastBitmap
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}
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if (eos) {
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outputEos = true
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return lastBitmap
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}
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// We've reached or passed the target — return this frame.
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if (ptsMs >= targetMs) {
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return lastBitmap
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// We've reached or passed the target — return this frame.
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if (ptsMs >= targetMs) {
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return lastBitmap
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}
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}
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}
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} catch (e: Exception) {
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Logger.w { "decodeUpTo failed at targetMs=$targetMs: ${e.message}" }
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release()
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throw e
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}
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return lastBitmap
···
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// Cached decoder — persists across extractFrame() calls for the same video.
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private var cachedDecoder: VideoFrameDecoder? = null
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private var cachedDecoderPath: String? = null
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private val decoderMutex = Mutex()
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actual suspend fun extractFrame(
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videoPath: String, frameTimestamp: Long
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): InputFrame? = withContext(Dispatchers.IO) {
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if (cachedDecoderPath != videoPath) {
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cachedDecoder?.release()
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cachedDecoder = VideoFrameDecoder(videoPath)
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cachedDecoderPath = videoPath
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}
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cachedDecoder!!.decodeUpTo(frameTimestamp)?.let {
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InputFrame(bitmap = it, timestamp = frameTimestamp)
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decoderMutex.withLock {
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try {
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if (cachedDecoderPath != videoPath) {
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cachedDecoder?.release()
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cachedDecoder = VideoFrameDecoder(videoPath)
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cachedDecoderPath = videoPath
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}
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cachedDecoder!!.decodeUpTo(frameTimestamp)?.let {
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InputFrame(bitmap = it, timestamp = frameTimestamp)
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}
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} catch (ce: CancellationException) {
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throw ce
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} catch (e: Exception) {
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Logger.w { "extractFrame failed, releasing decoder: ${e.message}" }
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cachedDecoder?.release()
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cachedDecoder = null
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cachedDecoderPath = null
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null
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}
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}
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}
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