Tweak multibuffer buffering strategy.

media/blink/multibuffer_data_source.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/blink/multibuffer_data_source.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
@@ skipping 549 matching lines @@
   // magnitude and clamp to prevent overflow.
   double playback_rate = playback_rate_;
 
   playback_rate = std::max(playback_rate, 1.0);
   playback_rate = std::min(playback_rate, kMaxPlaybackRate);
 
   int64_t bytes_per_second = (bitrate / 8.0) * playback_rate;
 
   int64_t preload = clamp(kTargetSecondsBufferedAhead * bytes_per_second,
                           kMinBufferPreload, kMaxBufferPreload);
+  int64_t preload_high = preload + kPreloadHighExtra;
+
+  // Assert that kMaxBufferSize is big enough that the subtraction on the next
+  // line cannot go negative.
+  static_assert(kMaxBufferSize > kMaxBufferPreload + kPreloadHighExtra,
+                "kMaxBufferSize too small to contain preload.");
   int64_t back_buffer = clamp(kTargetSecondsBufferedBehind * bytes_per_second,
-                              kMinBufferPreload, kMaxBufferPreload);
-  int64_t pin_forwards = kMaxBufferSize - back_buffer;
-  DCHECK_LE(preload + kPreloadHighExtra, pin_forwards);
-  reader_->SetMaxBuffer(back_buffer, preload + kPreloadHighExtra);
+                              kMinBufferPreload, kMaxBufferSize - preload_high);
+  int64_t buffer_size =
+      std::min((kTargetSecondsBufferedAhead + kTargetSecondsBufferedBehind) *
+                   bytes_per_second,
+               kMaxBufferSize);
+  reader_->SetMaxBuffer(buffer_size);
+  reader_->SetPinRange(back_buffer, kMaxBufferPreload + kPreloadHighExtra);
 
   if (preload_ == METADATA) {
     reader_->SetPreload(0, 0);
   } else {
-    reader_->SetPreload(preload + kPreloadHighExtra, preload);
+    reader_->SetPreload(preload_high, preload);
   }
 }
 
 }  // namespace media