Add callback in VideoDecoder and AudioDecoder to return decoded frames.

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 <algorithm>
 #include <string>
 
 #include "base/bind.h"
@@ skipping 117 matching lines @@
   video_frame.swap(reinterpret_cast<VideoFrame**>(&frame->opaque));
 
   // The FFmpeg API expects us to zero the data pointers in
   // this callback
   memset(frame->data, 0, sizeof(frame->data));
   frame->opaque = NULL;
 }
 
 void FFmpegVideoDecoder::Initialize(const VideoDecoderConfig& config,
                                     bool low_delay,
-                                    const PipelineStatusCB& status_cb) {
+                                    const PipelineStatusCB& status_cb,
+                                    const OutputCB& output_cb) {
   DCHECK(task_runner_->BelongsToCurrentThread());
-  DCHECK(decode_cb_.is_null());
   DCHECK(!config.is_encrypted());
+  DCHECK(!output_cb.is_null());
 
   FFmpegGlue::InitializeFFmpeg();
 
   config_ = config;
   PipelineStatusCB initialize_cb = BindToCurrentLoop(status_cb);
 
   if (!config.IsValidConfig() || !ConfigureDecoder(low_delay)) {
     initialize_cb.Run(DECODER_ERROR_NOT_SUPPORTED);
     return;
   }
 
+  output_cb_ = BindToCurrentLoop(output_cb);
+
   // Success!
   state_ = kNormal;
   initialize_cb.Run(PIPELINE_OK);
 }
 
 void FFmpegVideoDecoder::Decode(const scoped_refptr<DecoderBuffer>& buffer,
                                 const DecodeCB& decode_cb) {
   DCHECK(task_runner_->BelongsToCurrentThread());
+  DCHECK(buffer);
   DCHECK(!decode_cb.is_null());
   CHECK_NE(state_, kUninitialized);
-  CHECK(decode_cb_.is_null()) << "Overlapping decodes are not supported.";
-  decode_cb_ = BindToCurrentLoop(decode_cb);
+
+  DecodeCB decode_cb_bound = BindToCurrentLoop(decode_cb);
 
   if (state_ == kError) {
-    base::ResetAndReturn(&decode_cb_).Run(kDecodeError, NULL);
+    decode_cb_bound.Run(kDecodeError);
     return;
   }
 
   // Return empty frames if decoding has finished.
   if (state_ == kDecodeFinished) {

[xhwang, 2014/06/05 21:53:51]

nit: Probably this should never happen (DecoderStream won't call Decode() again
if decode has finished). But we can investigate this later.

[Sergey Ulanov, 2014/06/06 22:49:41]

Done.

[Sergey Ulanov, 2014/06/06 23:12:34]

Actually DecoderStream may call this method after EOS was returned. It should be
possible to fix it by adding EOS state in DecoderStream(), but I don't think it
has to be in this CL.

[xhwang, 2014/06/07 00:35:14]

Can you add a TODO here?

-    base::ResetAndReturn(&decode_cb_).Run(kOk, VideoFrame::CreateEOSFrame());
+    output_cb_.Run(VideoFrame::CreateEOSFrame());
+    decode_cb_bound.Run(kOk);
     return;
   }
 
-  DecodeBuffer(buffer);
-}
-
-void FFmpegVideoDecoder::Reset(const base::Closure& closure) {
-  DCHECK(task_runner_->BelongsToCurrentThread());
-  DCHECK(decode_cb_.is_null());
-
-  avcodec_flush_buffers(codec_context_.get());
-  state_ = kNormal;
-  task_runner_->PostTask(FROM_HERE, closure);
-}
-
-void FFmpegVideoDecoder::Stop() {
-  DCHECK(task_runner_->BelongsToCurrentThread());
-
-  if (state_ == kUninitialized)
-    return;
-
-  ReleaseFFmpegResources();
-  state_ = kUninitialized;
-}
-
-FFmpegVideoDecoder::~FFmpegVideoDecoder() {
-  DCHECK_EQ(kUninitialized, state_);
-  DCHECK(!codec_context_);
-  DCHECK(!av_frame_);
-}
-
-void FFmpegVideoDecoder::DecodeBuffer(
-    const scoped_refptr<DecoderBuffer>& buffer) {
-  DCHECK(task_runner_->BelongsToCurrentThread());
-  DCHECK_NE(state_, kUninitialized);
-  DCHECK_NE(state_, kDecodeFinished);
-  DCHECK_NE(state_, kError);
-  DCHECK(!decode_cb_.is_null());
-  DCHECK(buffer);
+  DCHECK_EQ(state_, kNormal);
 
   // During decode, because reads are issued asynchronously, it is possible to
   // receive multiple end of stream buffers since each decode 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
   //                until no more data is returned to flush out remaining
   //                frames. The input buffer is ignored at this point.

[xhwang, 2014/06/05 21:53:50]

this is obsolete now?

[Sergey Ulanov, 2014/06/06 22:49:41]

Done.

   //   kDecodeFinished: All calls return empty frames.
   //   kError: Unexpected error happened.
   //
   // These are the possible state transitions.
   //
-  // kNormal -> kFlushCodec:
-  //     When buffer->end_of_stream() is first true.
+  // kNormal -> kDecodeFinished:
+  //     When EOS buffer is received.

[xhwang, 2014/06/05 21:53:50]

When EOS buffer is received and the codec has been flushed.

[Sergey Ulanov, 2014/06/06 22:49:41]

Done.

   // kNormal -> kError:
   //     A decoding error occurs and decoding needs to stop.
-  // kFlushCodec -> kDecodeFinished:
-  //     When avcodec_decode_video2() returns 0 data.
-  // kFlushCodec -> kError:
-  //     When avcodec_decode_video2() errors out.
   // (any state) -> kNormal:
   //     Any time Reset() is called.
 
-  // Transition to kFlushCodec on the first end of stream buffer.
-  if (state_ == kNormal && buffer->end_of_stream()) {
-    state_ = kFlushCodec;
+  bool repeat;
+  do {
+    bool produced_frame = false;
+    if (!FFmpegDecode(buffer, &produced_frame)) {

[xhwang, 2014/06/05 21:53:50]

|produced_frame| could be read as a noun. How about |has_produced_frame|?

[Sergey Ulanov, 2014/06/06 22:49:41]

Done.

+      state_ = kError;
+      decode_cb_bound.Run(kDecodeError);
+      return;
+    }
+    // Repeat to flush the decoder after receiving EOS buffer.
+    repeat = buffer->end_of_stream() && produced_frame;
+  } while (repeat);

[xhwang, 2014/06/05 21:53:50]

nit: how about just 
while (buffer->end_of_stream() && produced_frame);
?

Felt that's slightly cleaner as it makes it clear that we only call
FFmpegDecode() multiple times when buffer->end_of_stream().

[Sergey Ulanov, 2014/06/06 22:49:41]

Done.

+
+  if (buffer->end_of_stream()) {
+    output_cb_.Run(VideoFrame::CreateEOSFrame());
+    state_ = kDecodeFinished;
   }
 
-  scoped_refptr<VideoFrame> video_frame;
-  if (!FFmpegDecode(buffer, &video_frame)) {
-    state_ = kError;
-    base::ResetAndReturn(&decode_cb_).Run(kDecodeError, NULL);
+  decode_cb_bound.Run(kOk);
+}
+
+void FFmpegVideoDecoder::Reset(const base::Closure& closure) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+
+  avcodec_flush_buffers(codec_context_.get());
+  state_ = kNormal;
+  task_runner_->PostTask(FROM_HERE, closure);
+}
+
+void FFmpegVideoDecoder::Stop() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+
+  if (state_ == kUninitialized)
     return;
-  }
 
-  if (!video_frame.get()) {
-    if (state_ == kFlushCodec) {
-      DCHECK(buffer->end_of_stream());
-      state_ = kDecodeFinished;
-      base::ResetAndReturn(&decode_cb_)
-          .Run(kOk, VideoFrame::CreateEOSFrame());
-      return;
-    }
+  ReleaseFFmpegResources();
+  state_ = kUninitialized;
+}
 
-    base::ResetAndReturn(&decode_cb_).Run(kNotEnoughData, NULL);
-    return;
-  }
-
-  base::ResetAndReturn(&decode_cb_).Run(kOk, video_frame);
+FFmpegVideoDecoder::~FFmpegVideoDecoder() {
+  DCHECK_EQ(kUninitialized, state_);
+  DCHECK(!codec_context_);
+  DCHECK(!av_frame_);
 }
 
 bool FFmpegVideoDecoder::FFmpegDecode(
     const scoped_refptr<DecoderBuffer>& buffer,
-    scoped_refptr<VideoFrame>* video_frame) {
-  DCHECK(video_frame);
+    bool* produced_frame) {
+  *produced_frame = false;

[xhwang, 2014/06/05 21:53:51]

DCHECK(!*produced_frame);

[Sergey Ulanov, 2014/06/06 22:49:41]

Done.

 
   // Reset frame to default values.
   avcodec_get_frame_defaults(av_frame_.get());
 
   // Create a packet for input data.
   // Due to FFmpeg API changes we no longer have const read-only pointers.
   AVPacket packet;
   av_init_packet(&packet);
   if (buffer->end_of_stream()) {
     packet.data = NULL;
@@ skipping 11 matching lines @@
   }
 
   int frame_decoded = 0;
   int result = avcodec_decode_video2(codec_context_.get(),
                                      av_frame_.get(),
                                      &frame_decoded,
                                      &packet);
   // Log the problem if we can't decode a video frame and exit early.
   if (result < 0) {
     LOG(ERROR) << "Error decoding video: " << buffer->AsHumanReadableString();
-    *video_frame = NULL;
     return false;
   }
 
   // If no frame was produced then signal that more data is required to
   // produce more frames. This can happen under two circumstances:
   //   1) Decoder was recently initialized/flushed
   //   2) End of stream was reached and all internal frames have been output
   if (frame_decoded == 0) {
-    *video_frame = NULL;
     return true;
   }
 
   // TODO(fbarchard): Work around for FFmpeg http://crbug.com/27675
   // The decoder is in a bad state and not decoding correctly.
   // Checking for NULL avoids a crash in CopyPlane().
   if (!av_frame_->data[VideoFrame::kYPlane] ||
       !av_frame_->data[VideoFrame::kUPlane] ||
       !av_frame_->data[VideoFrame::kVPlane]) {
     LOG(ERROR) << "Video frame was produced yet has invalid frame data.";
-    *video_frame = NULL;
     return false;
   }
 
   if (!av_frame_->opaque) {
     LOG(ERROR) << "VideoFrame object associated with frame data not set.";
     return false;
   }
-  *video_frame = static_cast<VideoFrame*>(av_frame_->opaque);
 
-  (*video_frame)->set_timestamp(
+  scoped_refptr<VideoFrame> frame = static_cast<VideoFrame*>(av_frame_->opaque);
+  frame->set_timestamp(
       base::TimeDelta::FromMicroseconds(av_frame_->reordered_opaque));
+  *produced_frame = true;
+  output_cb_.Run(frame);
 
   return true;
 }
 
 void FFmpegVideoDecoder::ReleaseFFmpegResources() {
   codec_context_.reset();
   av_frame_.reset();
 }
 
 bool FFmpegVideoDecoder::ConfigureDecoder(bool low_delay) {
@@ skipping 18 matching lines @@
   if (!codec || avcodec_open2(codec_context_.get(), codec, NULL) < 0) {
     ReleaseFFmpegResources();
     return false;
   }
 
   av_frame_.reset(av_frame_alloc());
   return true;
 }
 
 }  // namespace media