Make FFmpegVideoDecoder defer a flush until the pending read completes.

media/filters/ffmpeg_video_decoder.cc

 // Copyright (c) 2012 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/filters/ffmpeg_video_decoder.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/message_loop.h"
 #include "base/string_number_conversions.h"
@@ skipping 145 matching lines @@
   callback.Run();
 }
 
 void FFmpegVideoDecoder::Flush(const base::Closure& callback) {
   if (MessageLoop::current() != message_loop_) {
     message_loop_->PostTask(FROM_HERE, base::Bind(
         &FFmpegVideoDecoder::Flush, this, callback));
     return;
   }
 
+  flush_cb_ = callback;
+
+  // Defer the flush if a read is pending.
+  if (!read_cb_.is_null())
+    return;
+
+  DoFlush();
+}
+
+void FFmpegVideoDecoder::DoFlush() {
+  DCHECK(read_cb_.is_null());
+
   avcodec_flush_buffers(codec_context_);
   state_ = kNormal;
-  callback.Run();
+  flush_cb_.Run();
+  flush_cb_.Reset();
 }
 
 void FFmpegVideoDecoder::Read(const ReadCB& read_cb) {
   // Complete operation asynchronously on different stack of execution as per
   // the API contract of VideoDecoder::Read()
   message_loop_->PostTask(FROM_HERE, base::Bind(
       &FFmpegVideoDecoder::DoRead, this, read_cb));
 }
 
 const gfx::Size& FFmpegVideoDecoder::natural_size() {
@@ skipping 40 matching lines @@
   DCHECK_EQ(MessageLoop::current(), message_loop_);
   DCHECK_NE(state_, kUninitialized);
   DCHECK_NE(state_, kDecodeFinished);
   DCHECK(!read_cb_.is_null());
 
   if (!buffer) {
     DeliverFrame(NULL);
     return;
   }
 
+  if (!flush_cb_.is_null()) {
+    DeliverFrame(NULL);
+    DoFlush();
+    return;
+  }
+
   // During decode, because reads are issued asynchronously, it is possible to
   // receive multiple end of stream buffers since each read is acked. When the
   // first end of stream buffer is read, FFmpeg may still have frames queued
   // up in the decoder so we need to go through the decode loop until it stops
   // giving sensible data.  After that, the decoder should output empty
   // frames.  There are three states the decoder can be in:
   //
   //   kNormal: This is the starting state. Buffers are decoded. Decode errors
   //            are discarded.
   //   kFlushCodec: There isn't any more input data. Call avcodec_decode_video2
@@ skipping 178 matching lines @@
 scoped_refptr<VideoFrame> FFmpegVideoDecoder::AllocateVideoFrame() {
   VideoFrame::Format format = PixelFormatToVideoFormat(codec_context_->pix_fmt);
   size_t width = codec_context_->width;
   size_t height = codec_context_->height;
 
   return VideoFrame::CreateFrame(format, width, height,
                                  kNoTimestamp(), kNoTimestamp());
 }
 
 }  // namespace media