[MSE] Limit the number of samples stored in SourceBuffer

https://bugs.webkit.org/show_bug.cgi?id=258299

Reviewed by Philippe Normand.

Applications may append a lot of samples without triggering eviction algorithm (> 500K), which results in cleanup (on
player destruction) taking too long time.

This can easily happen in videos with a static image, for example a black screen, that are only focused on audio. Then
the video samples number can grow a lot because the samples themselves are not big and to achieve a big size, you can
need many of them. The result is that we have lots of objects if little data and it can take a long time to destruct them.

This change is no-op for non GStreamer ports and in GStreamer ports it allows to define an environment variable to limit
the number of samples.

Based on a patch by Eugene Mutavchi <Ievgen_Mutavchi@comcast.com>.

* Source/WebCore/platform/graphics/SourceBufferPrivate.cpp:
(WebCore::SourceBufferPrivate::platformEvictionThreshold const):
(WebCore::SourceBufferPrivate::hasTooManySamples const):
(WebCore::SourceBufferPrivate::evictCodedFrames):
* Source/WebCore/platform/graphics/SourceBufferPrivate.h:
* Source/WebCore/platform/graphics/gstreamer/mse/SourceBufferPrivateGStreamer.cpp:
(WebCore::SourceBufferPrivateGStreamer::platformEvictionThreshold const):
* Source/WebCore/platform/graphics/gstreamer/mse/SourceBufferPrivateGStreamer.h:

Canonical link: https://commits.webkit.org/265355@main

Source/WebCore/platform/graphics/SourceBufferPrivate.cpp

@@ -507,6 +507,23 @@ void SourceBufferPrivate::removeCodedFrames(const MediaTime& start, const MediaT
     updateBufferedFromTrackBuffers(trackBuffers, isEnded, WTFMove(completionHandler));
 }
 
+size_t SourceBufferPrivate::platformEvictionThreshold() const
+{
+    // Default implementation of the virtual function.
+    return 0;
+}
+
+bool SourceBufferPrivate::hasTooManySamples() const
+{
+    const size_t evictionThreshold = platformEvictionThreshold();
+    if (!evictionThreshold)
+        return false;
+    size_t currentSize = 0;
+    for (const auto& trackBuffer : m_trackBufferMap.values())
+        currentSize += trackBuffer->samples().size();
+    return currentSize > evictionThreshold;
+}
+
 void SourceBufferPrivate::evictCodedFrames(uint64_t newDataSize, uint64_t maximumBufferSize, const MediaTime& currentTime, bool isEnded)
 {
     // 3.5.13 Coded Frame Eviction Algorithm
@@ -518,7 +535,7 @@ void SourceBufferPrivate::evictCodedFrames(uint64_t newDataSize, uint64_t maximu
     // This algorithm is run to free up space in this source buffer when new data is appended.
     // 1. Let new data equal the data that is about to be appended to this SourceBuffer.
     // 2. If the buffer full flag equals false, then abort these steps.
-    bool isBufferFull = isBufferFullFor(newDataSize, maximumBufferSize);
+    bool isBufferFull = isBufferFullFor(newDataSize, maximumBufferSize) || hasTooManySamples();
     if (!isBufferFull)
         return;
 

Source/WebCore/platform/graphics/SourceBufferPrivate.h

@@ -97,6 +97,7 @@ class SourceBufferPrivate
     virtual void setShouldGenerateTimestamps(bool flag) { m_shouldGenerateTimestamps = flag; }
     WEBCORE_EXPORT virtual void removeCodedFrames(const MediaTime& start, const MediaTime& end, const MediaTime& currentMediaTime, bool isEnded, CompletionHandler<void()>&& = [] { });
     WEBCORE_EXPORT virtual void evictCodedFrames(uint64_t newDataSize, uint64_t maximumBufferSize, const MediaTime& currentTime, bool isEnded);
+    WEBCORE_EXPORT virtual size_t platformEvictionThreshold() const;
     WEBCORE_EXPORT virtual uint64_t totalTrackBufferSizeInBytes() const;
     WEBCORE_EXPORT virtual void resetTimestampOffsetInTrackBuffers();
     virtual void startChangingType() { m_pendingInitializationSegmentForChangeType = true; }
@@ -205,6 +206,7 @@ class SourceBufferPrivate
     bool evictFrames(uint64_t newDataSize, uint64_t maximumBufferSize, const MediaTime& currentTime, bool isEnded);
     bool isAttached() const;
     Vector<PlatformTimeRanges> trackBuffersRanges() const;
+    bool hasTooManySamples() const;
 
     bool m_hasAudio { false };
     bool m_hasVideo { false };

Source/WebCore/platform/graphics/gstreamer/mse/SourceBufferPrivateGStreamer.cpp

@@ -50,10 +50,7 @@
 #include "NotImplemented.h"
 #include "VideoTrackPrivateGStreamer.h"
 #include "WebKitMediaSourceGStreamer.h"
-
-#if PLATFORM(WPE)
 #include <wtf/text/StringToIntegerConversion.h>
-#endif
 
 GST_DEBUG_CATEGORY_EXTERN(webkit_mse_debug);
 #define GST_CAT_DEFAULT webkit_mse_debug
@@ -380,6 +377,18 @@ size_t SourceBufferPrivateGStreamer::platformMaximumBufferSize() const
     return 0;
 }
 
+size_t SourceBufferPrivateGStreamer::platformEvictionThreshold() const
+{
+    static size_t evictionThreshold = 0;
+    static std::once_flag once;
+    std::call_once(once, []() {
+        auto stringView = StringView::fromLatin1(std::getenv("MSE_BUFFER_SAMPLES_EVICTION_THRESHOLD"));
+        if (!stringView.isEmpty())
+            evictionThreshold = parseInteger<size_t>(stringView, 10).value_or(0);
+    });
+    return evictionThreshold;
+}
+
 #undef GST_CAT_DEFAULT
 
 } // namespace WebCore

Source/WebCore/platform/graphics/gstreamer/mse/SourceBufferPrivateGStreamer.h

@@ -95,6 +95,7 @@ class SourceBufferPrivateGStreamer final : public SourceBufferPrivate {
 #endif
 
     size_t platformMaximumBufferSize() const override;
+    size_t platformEvictionThreshold() const final;
 
 private:
     SourceBufferPrivateGStreamer(MediaSourcePrivateGStreamer*, const ContentType&, MediaPlayerPrivateGStreamerMSE&);