diff --git a/media/codec2/sfplugin/CCodecBufferChannel.cpp b/media/codec2/sfplugin/CCodecBufferChannel.cpp
index 83d3ada..8059ff6 100644
--- a/media/codec2/sfplugin/CCodecBufferChannel.cpp
+++ b/media/codec2/sfplugin/CCodecBufferChannel.cpp
@@ -128,97 +128,6 @@
     count->value = -1;
 }
 
-// CCodecBufferChannel::ReorderStash
-
-CCodecBufferChannel::ReorderStash::ReorderStash() {
-    clear();
-}
-
-void CCodecBufferChannel::ReorderStash::clear() {
-    mPending.clear();
-    mStash.clear();
-    mDepth = 0;
-    mKey = C2Config::ORDINAL;
-}
-
-void CCodecBufferChannel::ReorderStash::flush() {
-    mPending.clear();
-    mStash.clear();
-}
-
-void CCodecBufferChannel::ReorderStash::setDepth(uint32_t depth) {
-    mPending.splice(mPending.end(), mStash);
-    mDepth = depth;
-}
-
-void CCodecBufferChannel::ReorderStash::setKey(C2Config::ordinal_key_t key) {
-    mPending.splice(mPending.end(), mStash);
-    mKey = key;
-}
-
-bool CCodecBufferChannel::ReorderStash::pop(Entry *entry) {
-    if (mPending.empty()) {
-        return false;
-    }
-    entry->buffer     = mPending.front().buffer;
-    entry->timestamp  = mPending.front().timestamp;
-    entry->flags      = mPending.front().flags;
-    entry->ordinal    = mPending.front().ordinal;
-    mPending.pop_front();
-    return true;
-}
-
-void CCodecBufferChannel::ReorderStash::emplace(
-        const std::shared_ptr<C2Buffer> &buffer,
-        int64_t timestamp,
-        int32_t flags,
-        const C2WorkOrdinalStruct &ordinal) {
-    bool eos = flags & MediaCodec::BUFFER_FLAG_EOS;
-    if (!buffer && eos) {
-        // TRICKY: we may be violating ordering of the stash here. Because we
-        // don't expect any more emplace() calls after this, the ordering should
-        // not matter.
-        mStash.emplace_back(buffer, timestamp, flags, ordinal);
-    } else {
-        flags = flags & ~MediaCodec::BUFFER_FLAG_EOS;
-        auto it = mStash.begin();
-        for (; it != mStash.end(); ++it) {
-            if (less(ordinal, it->ordinal)) {
-                break;
-            }
-        }
-        mStash.emplace(it, buffer, timestamp, flags, ordinal);
-        if (eos) {
-            mStash.back().flags = mStash.back().flags | MediaCodec::BUFFER_FLAG_EOS;
-        }
-    }
-    while (!mStash.empty() && mStash.size() > mDepth) {
-        mPending.push_back(mStash.front());
-        mStash.pop_front();
-    }
-}
-
-void CCodecBufferChannel::ReorderStash::defer(
-        const CCodecBufferChannel::ReorderStash::Entry &entry) {
-    mPending.push_front(entry);
-}
-
-bool CCodecBufferChannel::ReorderStash::hasPending() const {
-    return !mPending.empty();
-}
-
-bool CCodecBufferChannel::ReorderStash::less(
-        const C2WorkOrdinalStruct &o1, const C2WorkOrdinalStruct &o2) {
-    switch (mKey) {
-        case C2Config::ORDINAL:   return o1.frameIndex < o2.frameIndex;
-        case C2Config::TIMESTAMP: return o1.timestamp < o2.timestamp;
-        case C2Config::CUSTOM:    return o1.customOrdinal < o2.customOrdinal;
-        default:
-            ALOGD("Unrecognized key; default to timestamp");
-            return o1.frameIndex < o2.frameIndex;
-    }
-}
-
 // Input
 
 CCodecBufferChannel::Input::Input() : extraBuffers("extra") {}
@@ -708,7 +617,7 @@
 
 void CCodecBufferChannel::feedInputBufferIfAvailableInternal() {
     if (mInputMetEos ||
-           mReorderStash.lock()->hasPending() ||
+           mOutput.lock()->buffers->hasPending() ||
            mPipelineWatcher.lock()->pipelineFull()) {
         return;
     } else {
@@ -989,17 +898,6 @@
         return UNKNOWN_ERROR;
     }
 
-    {
-        Mutexed<ReorderStash>::Locked reorder(mReorderStash);
-        reorder->clear();
-        if (reorderDepth) {
-            reorder->setDepth(reorderDepth.value);
-        }
-        if (reorderKey) {
-            reorder->setKey(reorderKey.value);
-        }
-    }
-
     uint32_t inputDelayValue = inputDelay ? inputDelay.value : 0;
     uint32_t pipelineDelayValue = pipelineDelay ? pipelineDelay.value : 0;
     uint32_t outputDelayValue = outputDelay ? outputDelay.value : 0;
@@ -1268,6 +1166,13 @@
         }
         output->buffers->setFormat(outputFormat);
 
+        output->buffers->clearStash();
+        if (reorderDepth) {
+            output->buffers->setReorderDepth(reorderDepth.value);
+        }
+        if (reorderKey) {
+            output->buffers->setReorderKey(reorderKey.value);
+        }
 
         // Try to set output surface to created block pool if given.
         if (outputSurface) {
@@ -1464,9 +1369,9 @@
         Mutexed<Output>::Locked output(mOutput);
         if (output->buffers) {
             output->buffers->flush(flushedWork);
+            output->buffers->flushStash();
         }
     }
-    mReorderStash.lock()->flush();
     mPipelineWatcher.lock()->flush();
 }
 
@@ -1507,45 +1412,36 @@
         if (!output->buffers) {
             return false;
         }
-        if (outputFormat != nullptr) {
-            ALOGD("[%s] onWorkDone: output format changed to %s",
-                    mName, outputFormat->debugString().c_str());
-            output->buffers->setFormat(outputFormat);
-
-            AString mediaType;
-            if (outputFormat->findString(KEY_MIME, &mediaType)
-                    && mediaType == MIMETYPE_AUDIO_RAW) {
-                int32_t channelCount;
-                int32_t sampleRate;
-                if (outputFormat->findInt32(KEY_CHANNEL_COUNT, &channelCount)
-                        && outputFormat->findInt32(KEY_SAMPLE_RATE, &sampleRate)) {
-                    output->buffers->updateSkipCutBuffer(sampleRate, channelCount);
-                }
-            }
-        }
     }
 
-    if ((work->input.ordinal.frameIndex - mFirstValidFrameIndex.load()).peek() < 0) {
+    // Whether the output buffer should be reported to the client or not.
+    bool notifyClient = false;
+
+    if (work->result == C2_OK){
+        notifyClient = true;
+    } else if (work->result == C2_NOT_FOUND) {
+        ALOGD("[%s] flushed work; ignored.", mName);
+    } else {
+        // C2_OK and C2_NOT_FOUND are the only results that we accept for processing
+        // the config update.
+        ALOGD("[%s] work failed to complete: %d", mName, work->result);
+        mCCodecCallback->onError(work->result, ACTION_CODE_FATAL);
+        return false;
+    }
+
+    if ((work->input.ordinal.frameIndex -
+            mFirstValidFrameIndex.load()).peek() < 0) {
         // Discard frames from previous generation.
         ALOGD("[%s] Discard frames from previous generation.", mName);
-        return false;
+        notifyClient = false;
     }
 
     if (mInputSurface == nullptr && (work->worklets.size() != 1u
             || !work->worklets.front()
-            || !(work->worklets.front()->output.flags & C2FrameData::FLAG_INCOMPLETE))) {
-        mPipelineWatcher.lock()->onWorkDone(work->input.ordinal.frameIndex.peeku());
-    }
-
-    if (work->result == C2_NOT_FOUND) {
-        ALOGD("[%s] flushed work; ignored.", mName);
-        return true;
-    }
-
-    if (work->result != C2_OK) {
-        ALOGD("[%s] work failed to complete: %d", mName, work->result);
-        mCCodecCallback->onError(work->result, ACTION_CODE_FATAL);
-        return false;
+            || !(work->worklets.front()->output.flags &
+                 C2FrameData::FLAG_INCOMPLETE))) {
+        mPipelineWatcher.lock()->onWorkDone(
+                work->input.ordinal.frameIndex.peeku());
     }
 
     // NOTE: MediaCodec usage supposedly have only one worklet
@@ -1581,8 +1477,10 @@
             case C2PortReorderBufferDepthTuning::CORE_INDEX: {
                 C2PortReorderBufferDepthTuning::output reorderDepth;
                 if (reorderDepth.updateFrom(*param)) {
-                    bool secure = mComponent->getName().find(".secure") != std::string::npos;
-                    mReorderStash.lock()->setDepth(reorderDepth.value);
+                    bool secure = mComponent->getName().find(".secure") !=
+                                  std::string::npos;
+                    mOutput.lock()->buffers->setReorderDepth(
+                            reorderDepth.value);
                     ALOGV("[%s] onWorkDone: updated reorder depth to %u",
                           mName, reorderDepth.value);
                     size_t numOutputSlots = mOutput.lock()->numSlots;
@@ -1594,17 +1492,19 @@
                         output->maxDequeueBuffers += numInputSlots;
                     }
                     if (output->surface) {
-                        output->surface->setMaxDequeuedBufferCount(output->maxDequeueBuffers);
+                        output->surface->setMaxDequeuedBufferCount(
+                                output->maxDequeueBuffers);
                     }
                 } else {
-                    ALOGD("[%s] onWorkDone: failed to read reorder depth", mName);
+                    ALOGD("[%s] onWorkDone: failed to read reorder depth",
+                          mName);
                 }
                 break;
             }
             case C2PortReorderKeySetting::CORE_INDEX: {
                 C2PortReorderKeySetting::output reorderKey;
                 if (reorderKey.updateFrom(*param)) {
-                    mReorderStash.lock()->setKey(reorderKey.value);
+                    mOutput.lock()->buffers->setReorderKey(reorderKey.value);
                     ALOGV("[%s] onWorkDone: updated reorder key to %u",
                           mName, reorderKey.value);
                 } else {
@@ -1619,7 +1519,8 @@
                         ALOGV("[%s] onWorkDone: updating pipeline delay %u",
                               mName, pipelineDelay.value);
                         newPipelineDelay = pipelineDelay.value;
-                        (void)mPipelineWatcher.lock()->pipelineDelay(pipelineDelay.value);
+                        (void)mPipelineWatcher.lock()->pipelineDelay(
+                                pipelineDelay.value);
                     }
                 }
                 if (param->forInput()) {
@@ -1628,7 +1529,8 @@
                         ALOGV("[%s] onWorkDone: updating input delay %u",
                               mName, inputDelay.value);
                         newInputDelay = inputDelay.value;
-                        (void)mPipelineWatcher.lock()->inputDelay(inputDelay.value);
+                        (void)mPipelineWatcher.lock()->inputDelay(
+                                inputDelay.value);
                     }
                 }
                 if (param->forOutput()) {
@@ -1636,8 +1538,10 @@
                     if (outputDelay.updateFrom(*param)) {
                         ALOGV("[%s] onWorkDone: updating output delay %u",
                               mName, outputDelay.value);
-                        bool secure = mComponent->getName().find(".secure") != std::string::npos;
-                        (void)mPipelineWatcher.lock()->outputDelay(outputDelay.value);
+                        bool secure = mComponent->getName().find(".secure") !=
+                                      std::string::npos;
+                        (void)mPipelineWatcher.lock()->outputDelay(
+                                outputDelay.value);
 
                         bool outputBuffersChanged = false;
                         size_t numOutputSlots = 0;
@@ -1648,7 +1552,8 @@
                                 return false;
                             }
                             output->outputDelay = outputDelay.value;
-                            numOutputSlots = outputDelay.value + kSmoothnessFactor;
+                            numOutputSlots = outputDelay.value +
+                                             kSmoothnessFactor;
                             if (output->numSlots < numOutputSlots) {
                                 output->numSlots = numOutputSlots;
                                 if (output->buffers->isArrayMode()) {
@@ -1667,7 +1572,7 @@
                             mCCodecCallback->onOutputBuffersChanged();
                         }
 
-                        uint32_t depth = mReorderStash.lock()->depth();
+                        uint32_t depth = mOutput.lock()->buffers->getReorderDepth();
                         Mutexed<OutputSurface>::Locked output(mOutputSurface);
                         output->maxDequeueBuffers = numOutputSlots + depth + kRenderingDepth;
                         if (!secure) {
@@ -1711,9 +1616,6 @@
         ALOGV("[%s] onWorkDone: output EOS", mName);
     }
 
-    sp<MediaCodecBuffer> outBuffer;
-    size_t index;
-
     // WORKAROUND: adjust output timestamp based on client input timestamp and codec
     // input timestamp. Codec output timestamp (in the timestamp field) shall correspond to
     // the codec input timestamp, but client output timestamp should (reported in timeUs)
@@ -1734,8 +1636,18 @@
           worklet->output.ordinal.timestamp.peekll(),
           timestamp.peekll());
 
+    // csd cannot be re-ordered and will always arrive first.
     if (initData != nullptr) {
         Mutexed<Output>::Locked output(mOutput);
+        if (output->buffers && outputFormat) {
+            output->buffers->updateSkipCutBuffer(outputFormat);
+            output->buffers->setFormat(outputFormat);
+        }
+        if (!notifyClient) {
+            return false;
+        }
+        size_t index;
+        sp<MediaCodecBuffer> outBuffer;
         if (output->buffers && output->buffers->registerCsd(initData, &index, &outBuffer) == OK) {
             outBuffer->meta()->setInt64("timeUs", timestamp.peek());
             outBuffer->meta()->setInt32("flags", MediaCodec::BUFFER_FLAG_CODECCONFIG);
@@ -1751,10 +1663,10 @@
         }
     }
 
-    if (!buffer && !flags) {
+    if (notifyClient && !buffer && !flags) {
         ALOGV("[%s] onWorkDone: Not reporting output buffer (%lld)",
               mName, work->input.ordinal.frameIndex.peekull());
-        return true;
+        notifyClient = false;
     }
 
     if (buffer) {
@@ -1773,66 +1685,62 @@
     }
 
     {
-        Mutexed<ReorderStash>::Locked reorder(mReorderStash);
-        reorder->emplace(buffer, timestamp.peek(), flags, worklet->output.ordinal);
-        if (flags & MediaCodec::BUFFER_FLAG_EOS) {
-            // Flush reorder stash
-            reorder->setDepth(0);
-        }
+        Mutexed<Output>::Locked output(mOutput);
+        output->buffers->pushToStash(
+                buffer,
+                notifyClient,
+                timestamp.peek(),
+                flags,
+                outputFormat,
+                worklet->output.ordinal);
     }
     sendOutputBuffers();
     return true;
 }
 
 void CCodecBufferChannel::sendOutputBuffers() {
-    ReorderStash::Entry entry;
-    sp<MediaCodecBuffer> outBuffer;
+    OutputBuffers::BufferAction action;
     size_t index;
+    sp<MediaCodecBuffer> outBuffer;
+    std::shared_ptr<C2Buffer> c2Buffer;
 
     while (true) {
-        Mutexed<ReorderStash>::Locked reorder(mReorderStash);
-        if (!reorder->hasPending()) {
-            break;
-        }
-        if (!reorder->pop(&entry)) {
-            break;
-        }
-
         Mutexed<Output>::Locked output(mOutput);
         if (!output->buffers) {
             return;
         }
-        status_t err = output->buffers->registerBuffer(entry.buffer, &index, &outBuffer);
-        if (err != OK) {
-            bool outputBuffersChanged = false;
-            if (err != WOULD_BLOCK) {
-                if (!output->buffers->isArrayMode()) {
-                    output->buffers = output->buffers->toArrayMode(output->numSlots);
-                }
-                OutputBuffersArray *array = (OutputBuffersArray *)output->buffers.get();
-                array->realloc(entry.buffer);
-                outputBuffersChanged = true;
-            }
-            ALOGV("[%s] sendOutputBuffers: unable to register output buffer", mName);
-            reorder->defer(entry);
-
+        action = output->buffers->popFromStashAndRegister(
+                &c2Buffer, &index, &outBuffer);
+        switch (action) {
+        case OutputBuffers::SKIP:
+            return;
+        case OutputBuffers::DISCARD:
+            break;
+        case OutputBuffers::NOTIFY_CLIENT:
             output.unlock();
-            reorder.unlock();
-
-            if (outputBuffersChanged) {
-                mCCodecCallback->onOutputBuffersChanged();
+            mCallback->onOutputBufferAvailable(index, outBuffer);
+            break;
+        case OutputBuffers::REALLOCATE:
+            if (!output->buffers->isArrayMode()) {
+                output->buffers =
+                    output->buffers->toArrayMode(output->numSlots);
             }
+            static_cast<OutputBuffersArray*>(output->buffers.get())->
+                    realloc(c2Buffer);
+            output.unlock();
+            mCCodecCallback->onOutputBuffersChanged();
+            return;
+        case OutputBuffers::RETRY:
+            ALOGV("[%s] sendOutputBuffers: unable to register output buffer",
+                  mName);
+            return;
+        default:
+            LOG_ALWAYS_FATAL("[%s] sendOutputBuffers: "
+                    "corrupted BufferAction value (%d) "
+                    "returned from popFromStashAndRegister.",
+                    mName, int(action));
             return;
         }
-        output.unlock();
-        reorder.unlock();
-
-        outBuffer->meta()->setInt64("timeUs", entry.timestamp);
-        outBuffer->meta()->setInt32("flags", entry.flags);
-        ALOGV("[%s] sendOutputBuffers: out buffer index = %zu [%p] => %p + %zu (%lld)",
-                mName, index, outBuffer.get(), outBuffer->data(), outBuffer->size(),
-                (long long)entry.timestamp);
-        mCallback->onOutputBufferAvailable(index, outBuffer);
     }
 }
 
diff --git a/media/codec2/sfplugin/CCodecBufferChannel.h b/media/codec2/sfplugin/CCodecBufferChannel.h
index f6e7024..046c5c3 100644
--- a/media/codec2/sfplugin/CCodecBufferChannel.h
+++ b/media/codec2/sfplugin/CCodecBufferChannel.h
@@ -306,48 +306,6 @@
 
     Mutexed<PipelineWatcher> mPipelineWatcher;
 
-    class ReorderStash {
-    public:
-        struct Entry {
-            inline Entry() : buffer(nullptr), timestamp(0), flags(0), ordinal({0, 0, 0}) {}
-            inline Entry(
-                    const std::shared_ptr<C2Buffer> &b,
-                    int64_t t,
-                    int32_t f,
-                    const C2WorkOrdinalStruct &o)
-                : buffer(b), timestamp(t), flags(f), ordinal(o) {}
-            std::shared_ptr<C2Buffer> buffer;
-            int64_t timestamp;
-            int32_t flags;
-            C2WorkOrdinalStruct ordinal;
-        };
-
-        ReorderStash();
-
-        void clear();
-        void flush();
-        void setDepth(uint32_t depth);
-        void setKey(C2Config::ordinal_key_t key);
-        bool pop(Entry *entry);
-        void emplace(
-                const std::shared_ptr<C2Buffer> &buffer,
-                int64_t timestamp,
-                int32_t flags,
-                const C2WorkOrdinalStruct &ordinal);
-        void defer(const Entry &entry);
-        bool hasPending() const;
-        uint32_t depth() const { return mDepth; }
-
-    private:
-        std::list<Entry> mPending;
-        std::list<Entry> mStash;
-        uint32_t mDepth;
-        C2Config::ordinal_key_t mKey;
-
-        bool less(const C2WorkOrdinalStruct &o1, const C2WorkOrdinalStruct &o2);
-    };
-    Mutexed<ReorderStash> mReorderStash;
-
     std::atomic_bool mInputMetEos;
     std::once_flag mRenderWarningFlag;
 
diff --git a/media/codec2/sfplugin/CCodecBuffers.cpp b/media/codec2/sfplugin/CCodecBuffers.cpp
index a9120c4..e58a1e4 100644
--- a/media/codec2/sfplugin/CCodecBuffers.cpp
+++ b/media/codec2/sfplugin/CCodecBuffers.cpp
@@ -21,6 +21,7 @@
 #include <C2PlatformSupport.h>
 
 #include <media/stagefright/foundation/ADebug.h>
+#include <media/stagefright/MediaCodec.h>
 #include <media/stagefright/MediaCodecConstants.h>
 #include <media/stagefright/SkipCutBuffer.h>
 #include <mediadrm/ICrypto.h>
@@ -155,16 +156,29 @@
     setSkipCutBuffer(delay, padding);
 }
 
+void OutputBuffers::updateSkipCutBuffer(
+        const sp<AMessage> &format, bool notify) {
+    AString mediaType;
+    if (format->findString(KEY_MIME, &mediaType)
+            && mediaType == MIMETYPE_AUDIO_RAW) {
+        int32_t channelCount;
+        int32_t sampleRate;
+        if (format->findInt32(KEY_CHANNEL_COUNT, &channelCount)
+                && format->findInt32(KEY_SAMPLE_RATE, &sampleRate)) {
+            updateSkipCutBuffer(sampleRate, channelCount);
+        }
+    }
+    if (notify) {
+        mUnreportedFormat = nullptr;
+    }
+}
+
 void OutputBuffers::submit(const sp<MediaCodecBuffer> &buffer) {
     if (mSkipCutBuffer != nullptr) {
         mSkipCutBuffer->submit(buffer);
     }
 }
 
-void OutputBuffers::transferSkipCutBuffer(const sp<SkipCutBuffer> &scb) {
-    mSkipCutBuffer = scb;
-}
-
 void OutputBuffers::setSkipCutBuffer(int32_t skip, int32_t cut) {
     if (mSkipCutBuffer != nullptr) {
         size_t prevSize = mSkipCutBuffer->size();
@@ -175,6 +189,175 @@
     mSkipCutBuffer = new SkipCutBuffer(skip, cut, mChannelCount);
 }
 
+void OutputBuffers::clearStash() {
+    mPending.clear();
+    mReorderStash.clear();
+    mDepth = 0;
+    mKey = C2Config::ORDINAL;
+    mUnreportedFormat = nullptr;
+}
+
+void OutputBuffers::flushStash() {
+    for (StashEntry& e : mPending) {
+        e.notify = false;
+    }
+    for (StashEntry& e : mReorderStash) {
+        e.notify = false;
+    }
+}
+
+uint32_t OutputBuffers::getReorderDepth() const {
+    return mDepth;
+}
+
+void OutputBuffers::setReorderDepth(uint32_t depth) {
+    mPending.splice(mPending.end(), mReorderStash);
+    mDepth = depth;
+}
+
+void OutputBuffers::setReorderKey(C2Config::ordinal_key_t key) {
+    mPending.splice(mPending.end(), mReorderStash);
+    mKey = key;
+}
+
+void OutputBuffers::pushToStash(
+        const std::shared_ptr<C2Buffer>& buffer,
+        bool notify,
+        int64_t timestamp,
+        int32_t flags,
+        const sp<AMessage>& format,
+        const C2WorkOrdinalStruct& ordinal) {
+    bool eos = flags & MediaCodec::BUFFER_FLAG_EOS;
+    if (!buffer && eos) {
+        // TRICKY: we may be violating ordering of the stash here. Because we
+        // don't expect any more emplace() calls after this, the ordering should
+        // not matter.
+        mReorderStash.emplace_back(
+                buffer, notify, timestamp, flags, format, ordinal);
+    } else {
+        flags = flags & ~MediaCodec::BUFFER_FLAG_EOS;
+        auto it = mReorderStash.begin();
+        for (; it != mReorderStash.end(); ++it) {
+            if (less(ordinal, it->ordinal)) {
+                break;
+            }
+        }
+        mReorderStash.emplace(it,
+                buffer, notify, timestamp, flags, format, ordinal);
+        if (eos) {
+            mReorderStash.back().flags =
+                mReorderStash.back().flags | MediaCodec::BUFFER_FLAG_EOS;
+        }
+    }
+    while (!mReorderStash.empty() && mReorderStash.size() > mDepth) {
+        mPending.push_back(mReorderStash.front());
+        mReorderStash.pop_front();
+    }
+    ALOGV("[%s] %s: pushToStash -- pending size = %zu", mName, __func__, mPending.size());
+}
+
+OutputBuffers::BufferAction OutputBuffers::popFromStashAndRegister(
+        std::shared_ptr<C2Buffer>* c2Buffer,
+        size_t* index,
+        sp<MediaCodecBuffer>* outBuffer) {
+    if (mPending.empty()) {
+        return SKIP;
+    }
+
+    // Retrieve the first entry.
+    StashEntry &entry = mPending.front();
+
+    *c2Buffer = entry.buffer;
+    sp<AMessage> outputFormat = entry.format;
+
+    // The output format can be processed without a registered slot.
+    if (outputFormat) {
+        ALOGD("[%s] popFromStashAndRegister: output format changed to %s",
+                mName, outputFormat->debugString().c_str());
+        updateSkipCutBuffer(outputFormat, entry.notify);
+    }
+
+    if (entry.notify) {
+        if (outputFormat) {
+            setFormat(outputFormat);
+        } else if (mUnreportedFormat) {
+            outputFormat = mUnreportedFormat;
+            setFormat(outputFormat);
+        }
+        mUnreportedFormat = nullptr;
+    } else {
+        if (outputFormat) {
+            mUnreportedFormat = outputFormat;
+        } else if (!mUnreportedFormat) {
+            mUnreportedFormat = mFormat;
+        }
+    }
+
+    // Flushing mReorderStash because no other buffers should come after output
+    // EOS.
+    if (entry.flags & MediaCodec::BUFFER_FLAG_EOS) {
+        // Flush reorder stash
+        setReorderDepth(0);
+    }
+
+    if (!entry.notify) {
+        mPending.pop_front();
+        return DISCARD;
+    }
+
+    // Try to register the buffer.
+    status_t err = registerBuffer(*c2Buffer, index, outBuffer);
+    if (err != OK) {
+        if (err != WOULD_BLOCK) {
+            return REALLOCATE;
+        }
+        return RETRY;
+    }
+
+    // Append information from the front stash entry to outBuffer.
+    (*outBuffer)->meta()->setInt64("timeUs", entry.timestamp);
+    (*outBuffer)->meta()->setInt32("flags", entry.flags);
+    ALOGV("[%s] popFromStashAndRegister: "
+          "out buffer index = %zu [%p] => %p + %zu (%lld)",
+          mName, *index, outBuffer->get(),
+          (*outBuffer)->data(), (*outBuffer)->size(),
+          (long long)entry.timestamp);
+
+    // The front entry of mPending will be removed now that the registration
+    // succeeded.
+    mPending.pop_front();
+    return NOTIFY_CLIENT;
+}
+
+bool OutputBuffers::popPending(StashEntry *entry) {
+    if (mPending.empty()) {
+        return false;
+    }
+    *entry = mPending.front();
+    mPending.pop_front();
+    return true;
+}
+
+void OutputBuffers::deferPending(const OutputBuffers::StashEntry &entry) {
+    mPending.push_front(entry);
+}
+
+bool OutputBuffers::hasPending() const {
+    return !mPending.empty();
+}
+
+bool OutputBuffers::less(
+        const C2WorkOrdinalStruct &o1, const C2WorkOrdinalStruct &o2) const {
+    switch (mKey) {
+        case C2Config::ORDINAL:   return o1.frameIndex < o2.frameIndex;
+        case C2Config::TIMESTAMP: return o1.timestamp < o2.timestamp;
+        case C2Config::CUSTOM:    return o1.customOrdinal < o2.customOrdinal;
+        default:
+            ALOGD("Unrecognized key; default to timestamp");
+            return o1.frameIndex < o2.frameIndex;
+    }
+}
+
 // LocalBufferPool
 
 constexpr size_t kInitialPoolCapacity = kMaxLinearBufferSize;
@@ -981,6 +1164,16 @@
     mImpl.grow(newSize, mAlloc);
 }
 
+void OutputBuffersArray::transferFrom(OutputBuffers* source) {
+    mFormat = source->mFormat;
+    mSkipCutBuffer = source->mSkipCutBuffer;
+    mUnreportedFormat = source->mUnreportedFormat;
+    mPending = std::move(source->mPending);
+    mReorderStash = std::move(source->mReorderStash);
+    mDepth = source->mDepth;
+    mKey = source->mKey;
+}
+
 // FlexOutputBuffers
 
 status_t FlexOutputBuffers::registerBuffer(
@@ -1023,13 +1216,12 @@
     // track of the flushed work.
 }
 
-std::unique_ptr<OutputBuffers> FlexOutputBuffers::toArrayMode(size_t size) {
+std::unique_ptr<OutputBuffersArray> FlexOutputBuffers::toArrayMode(size_t size) {
     std::unique_ptr<OutputBuffersArray> array(new OutputBuffersArray(mComponentName.c_str()));
-    array->setFormat(mFormat);
-    array->transferSkipCutBuffer(mSkipCutBuffer);
+    array->transferFrom(this);
     std::function<sp<Codec2Buffer>()> alloc = getAlloc();
     array->initialize(mImpl, size, alloc);
-    return std::move(array);
+    return array;
 }
 
 size_t FlexOutputBuffers::numClientBuffers() const {
diff --git a/media/codec2/sfplugin/CCodecBuffers.h b/media/codec2/sfplugin/CCodecBuffers.h
index eec79f1..0d4fa81 100644
--- a/media/codec2/sfplugin/CCodecBuffers.h
+++ b/media/codec2/sfplugin/CCodecBuffers.h
@@ -156,6 +156,8 @@
     DISALLOW_EVIL_CONSTRUCTORS(InputBuffers);
 };
 
+class OutputBuffersArray;
+
 class OutputBuffers : public CCodecBuffers {
 public:
     OutputBuffers(const char *componentName, const char *name = "Output");
@@ -163,8 +165,12 @@
 
     /**
      * Register output C2Buffer from the component and obtain corresponding
-     * index and MediaCodecBuffer object. Returns false if registration
-     * fails.
+     * index and MediaCodecBuffer object.
+     *
+     * Returns:
+     *   OK if registration succeeds.
+     *   NO_MEMORY if all buffers are available but not compatible.
+     *   WOULD_BLOCK if there are compatible buffers, but they are all in use.
      */
     virtual status_t registerBuffer(
             const std::shared_ptr<C2Buffer> &buffer,
@@ -199,7 +205,7 @@
      * shall retain the internal state so that it will honor index and
      * buffer from previous calls of registerBuffer().
      */
-    virtual std::unique_ptr<OutputBuffers> toArrayMode(size_t size) = 0;
+    virtual std::unique_ptr<OutputBuffersArray> toArrayMode(size_t size) = 0;
 
     /**
      * Initialize SkipCutBuffer object.
@@ -208,6 +214,164 @@
             int32_t delay, int32_t padding, int32_t sampleRate, int32_t channelCount);
 
     /**
+     * Update SkipCutBuffer from format. The @p format must not be null.
+     * @p notify determines whether the format comes with a buffer that should
+     * be reported to the client or not.
+     */
+    void updateSkipCutBuffer(const sp<AMessage> &format, bool notify = true);
+
+    /**
+     * Output Stash
+     * ============
+     *
+     * The output stash is a place to hold output buffers temporarily before
+     * they are registered to output slots. It has 2 main functions:
+     * 1. Allow reordering of output frames as the codec may produce frames in a
+     *    different order.
+     * 2. Act as a "buffer" between the codec and the client because the codec
+     *    may produce more buffers than available slots. This excess of codec's
+     *    output buffers should be registered to slots later, after the client
+     *    has released some slots.
+     *
+     * The stash consists of 2 lists of buffers: mPending and mReorderStash.
+     * mPending is a normal FIFO queue with not size limit, while mReorderStash
+     * is a sorted list with size limit mDepth.
+     *
+     * The normal flow of a non-csd output buffer is as follows:
+     *
+     *           |----------------OutputBuffers---------------|
+     *           |----------Output stash----------|           |
+     *   Codec --|-> mReorderStash --> mPending --|-> slots --|-> client
+     *           |                                |           |
+     *     pushToStash()                    popFromStashAndRegister()
+     *
+     * The buffer that comes from the codec first enters mReorderStash. The
+     * first buffer in mReorderStash gets moved to mPending when mReorderStash
+     * overflows. Buffers in mPending are registered to slots and given to the
+     * client as soon as slots are available.
+     *
+     * Every output buffer that is not a csd buffer should be put on the stash
+     * by calling pushToStash(), then later registered to a slot by calling
+     * popFromStashAndRegister() before notifying the client with
+     * onOutputBufferAvailable().
+     *
+     * Reordering
+     * ==========
+     *
+     * mReorderStash is a sorted list with a specified size limit. The size
+     * limit can be set by calling setReorderDepth().
+     *
+     * Every buffer in mReorderStash has a C2WorkOrdinalStruct, which contains 3
+     * members, all of which are comparable. Which member of C2WorkOrdinalStruct
+     * should be used for reordering can be chosen by calling setReorderKey().
+     */
+
+    /**
+     * Return the reorder depth---the size of mReorderStash.
+     */
+    uint32_t getReorderDepth() const;
+
+    /**
+     * Set the reorder depth.
+     */
+    void setReorderDepth(uint32_t depth);
+
+    /**
+     * Set the type of "key" to use in comparisons.
+     */
+    void setReorderKey(C2Config::ordinal_key_t key);
+
+    /**
+     * Return whether the output stash has any pending buffers.
+     */
+    bool hasPending() const;
+
+    /**
+     * Flush the stash and reset the depth and the key to their default values.
+     */
+    void clearStash();
+
+    /**
+     * Flush the stash.
+     */
+    void flushStash();
+
+    /**
+     * Push a buffer to the reorder stash.
+     *
+     * @param buffer    C2Buffer object from the returned work.
+     * @param notify    Whether the returned work contains a buffer that should
+     *                  be reported to the client. This may be false if the
+     *                  caller wants to process the buffer without notifying the
+     *                  client.
+     * @param timestamp Buffer timestamp to report to the client.
+     * @param flags     Buffer flags to report to the client.
+     * @param format    Buffer format to report to the client.
+     * @param ordinal   Ordinal used in reordering. This determines when the
+     *                  buffer will be popped from the output stash by
+     *                  `popFromStashAndRegister()`.
+     */
+    void pushToStash(
+            const std::shared_ptr<C2Buffer>& buffer,
+            bool notify,
+            int64_t timestamp,
+            int32_t flags,
+            const sp<AMessage>& format,
+            const C2WorkOrdinalStruct& ordinal);
+
+    enum BufferAction : int {
+        SKIP,
+        DISCARD,
+        NOTIFY_CLIENT,
+        REALLOCATE,
+        RETRY,
+    };
+
+    /**
+     * Try to atomically pop the first buffer from the reorder stash and
+     * register it to an output slot. The function returns a value that
+     * indicates a recommended course of action for the caller.
+     *
+     * If the stash is empty, the function will return `SKIP`.
+     *
+     * If the stash is not empty, the function will peek at the first (oldest)
+     * entry in mPending process the buffer in the entry as follows:
+     * - If the buffer should not be sent to the client, the function will
+     *   return `DISCARD`. The stash entry will be removed.
+     * - If the buffer should be sent to the client, the function will attempt
+     *   to register the buffer to a slot. The registration may have 3 outcomes
+     *   corresponding to the following return values:
+     *   - `NOTIFY_CLIENT`: The buffer is successfully registered to a slot. The
+     *     output arguments @p index and @p outBuffer will contain valid values
+     *     that the caller can use to call onOutputBufferAvailable(). The stash
+     *     entry will be removed.
+     *   - `REALLOCATE`: The buffer is not registered because it is not
+     *     compatible with the current slots (which are available). The caller
+     *     should reallocate the OutputBuffers with slots that can fit the
+     *     returned @p c2Buffer. The stash entry will not be removed
+     *   - `RETRY`: All slots are currently occupied by the client. The caller
+     *     should try to call this function again after the client has released
+     *     some slots.
+     *
+     * @return What the caller should do afterwards.
+     *
+     * @param[out] c2Buffer   Underlying C2Buffer associated to the first buffer
+     *                        on the stash. This value is guaranteed to be valid
+     *                        unless the return value is `SKIP`.
+     * @param[out] index      Slot index. This value is valid only if the return
+     *                        value is `NOTIFY_CLIENT`.
+     * @param[out] outBuffer  Registered buffer. This value is valid only if the
+     *                        return valu is `NOTIFY_CLIENT`.
+     */
+    BufferAction popFromStashAndRegister(
+            std::shared_ptr<C2Buffer>* c2Buffer,
+            size_t* index,
+            sp<MediaCodecBuffer>* outBuffer);
+
+protected:
+    sp<SkipCutBuffer> mSkipCutBuffer;
+
+    /**
      * Update the SkipCutBuffer object. No-op if it's never initialized.
      */
     void updateSkipCutBuffer(int32_t sampleRate, int32_t channelCount);
@@ -217,15 +381,8 @@
      */
     void submit(const sp<MediaCodecBuffer> &buffer);
 
-    /**
-     * Transfer SkipCutBuffer object to the other Buffers object.
-     */
-    void transferSkipCutBuffer(const sp<SkipCutBuffer> &scb);
-
-protected:
-    sp<SkipCutBuffer> mSkipCutBuffer;
-
 private:
+    // SkipCutBuffer
     int32_t mDelay;
     int32_t mPadding;
     int32_t mSampleRate;
@@ -233,7 +390,78 @@
 
     void setSkipCutBuffer(int32_t skip, int32_t cut);
 
+    // Output stash
+
+    // Output format that has not been made available to the client.
+    sp<AMessage> mUnreportedFormat;
+
+    // Struct for an entry in the output stash (mPending and mReorderStash)
+    struct StashEntry {
+        inline StashEntry()
+            : buffer(nullptr),
+              notify(false),
+              timestamp(0),
+              flags(0),
+              format(),
+              ordinal({0, 0, 0}) {}
+        inline StashEntry(
+                const std::shared_ptr<C2Buffer> &b,
+                bool n,
+                int64_t t,
+                int32_t f,
+                const sp<AMessage> &fmt,
+                const C2WorkOrdinalStruct &o)
+            : buffer(b),
+              notify(n),
+              timestamp(t),
+              flags(f),
+              format(fmt),
+              ordinal(o) {}
+        std::shared_ptr<C2Buffer> buffer;
+        bool notify;
+        int64_t timestamp;
+        int32_t flags;
+        sp<AMessage> format;
+        C2WorkOrdinalStruct ordinal;
+    };
+
+    /**
+     * FIFO queue of stash entries.
+     */
+    std::list<StashEntry> mPending;
+    /**
+     * Sorted list of stash entries.
+     */
+    std::list<StashEntry> mReorderStash;
+    /**
+     * Size limit of mReorderStash.
+     */
+    uint32_t mDepth{0};
+    /**
+     * Choice of key to use in ordering of stash entries in mReorderStash.
+     */
+    C2Config::ordinal_key_t mKey{C2Config::ORDINAL};
+
+    /**
+     * Return false if mPending is empty; otherwise, pop the first entry from
+     * mPending and return true.
+     */
+    bool popPending(StashEntry *entry);
+
+    /**
+     * Push an entry as the first entry of mPending.
+     */
+    void deferPending(const StashEntry &entry);
+
+    /**
+     * Comparison of C2WorkOrdinalStruct based on mKey.
+     */
+    bool less(const C2WorkOrdinalStruct &o1,
+              const C2WorkOrdinalStruct &o2) const;
+
     DISALLOW_EVIL_CONSTRUCTORS(OutputBuffers);
+
+    friend OutputBuffersArray;
 };
 
 /**
@@ -770,7 +998,7 @@
 
     bool isArrayMode() const final { return true; }
 
-    std::unique_ptr<OutputBuffers> toArrayMode(size_t) final {
+    std::unique_ptr<OutputBuffersArray> toArrayMode(size_t) final {
         return nullptr;
     }
 
@@ -809,6 +1037,12 @@
      */
     void grow(size_t newSize);
 
+    /**
+     * Transfer the SkipCutBuffer and the output stash from another
+     * OutputBuffers.
+     */
+    void transferFrom(OutputBuffers* source);
+
 private:
     BuffersArrayImpl mImpl;
     std::function<sp<Codec2Buffer>()> mAlloc;
@@ -837,7 +1071,7 @@
     void flush(
             const std::list<std::unique_ptr<C2Work>> &flushedWork) override;
 
-    std::unique_ptr<OutputBuffers> toArrayMode(size_t size) override;
+    std::unique_ptr<OutputBuffersArray> toArrayMode(size_t size) override;
 
     size_t numClientBuffers() const final;