Add CDM video decoder.

webkit/media/crypto/ppapi/ffmpeg_cdm_video_decoder.h

+// 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.
+
+#ifndef WEBKIT_MEDIA_CRYPTO_PPAPI_FFMPEG_CDM_VIDEO_DECODER_H_
+#define WEBKIT_MEDIA_CRYPTO_PPAPI_FFMPEG_CDM_VIDEO_DECODER_H_
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/memory/ref_counted.h"

[ddorwin, 2012/10/16 18:04:30]

What is ref counted?

[Tom Finegan, 2012/10/16 21:44:44]

Removed, vestige of media/filters/ffmpeg_video_decoder.cc ancestry.

+#include "webkit/media/crypto/ppapi/content_decryption_module.h"
+
+struct AVCodecContext;
+struct AVFrame;
+
+namespace webkit_media {
+
+static const uint32_t kBufferAlignment = 32;
+static const uint32_t kBufferPadBytes = kBufferAlignment - 1;
+static const int kDecodeThreads = 1;
+
+bool IsValidConfig(cdm::VideoFormat format, const cdm::Size& data_size);

[ddorwin, 2012/10/16 18:04:30]

Should this all be in the cdm namespace? It's only used by the cdm. Also, it
uses cdm types. This function is the most important to get right since it's just
sitting in the webkit_media namespace.

[Tom Finegan, 2012/10/16 21:44:44]

This should not have been here. Made it a static member of FFmpegCdmVideoFrame
since confirming that video frame creation is possible is the purpose of the
config validation.

+
+class FFmpegCdmVideoDecoder {
+ public:
+  FFmpegCdmVideoDecoder(cdm::Allocator* allocator);
+  ~FFmpegCdmVideoDecoder();
+  bool Initialize(const cdm::VideoDecoderConfig& config);
+  void Deinitialize();
+  void Reset();
+
+  // Decodes |compressed_frame|, and stores decoded frame in |decoded_frame|
+  // when an output frame is available. Returns true when when successful.

[ddorwin, 2012/10/16 18:04:30]

"Returns whether the call was successful."

Then you can drop the last sentence below.

[Tom Finegan, 2012/10/16 21:44:44]

Done.

+  // Note: This method can return true with a null |decoded_frame|. This occurs
+  // when the decoder needs more data to produce an output video frame. Returns
+  // false upon failure.

[xhwang, 2012/10/16 21:59:53]

During EOS, we'll call DecodeFrame with NULL input until there's no output
available, in which case the return is true and the output is NULL. We should be
able to distinguish this case with NoMoreData.

[Tom Finegan, 2012/10/17 02:39:10]

Method returns cdm::Status now, as it should have to begin with. Sorry about
that, for some reason I thought CDM::DecryptAndDecodeFrame returned bool. 

+  bool DecodeFrame(const uint8_t* compressed_frame,
+                   int32_t compressed_frame_size,
+                   int64_t timestamp,
+                   cdm::VideoFrame* decoded_frame);
+
+  // Callback called from within FFmpeg to allocate a buffer based on
+  // the dimensions of |codec_context|. See AVCodecContext.get_buffer
+  // documentation inside FFmpeg.
+  int GetVideoBuffer(AVCodecContext* codec_context, AVFrame* frame);

[ddorwin, 2012/10/16 18:04:30]

Can this be private? It's provided to FFmpeg as a pointer, right?

[Tom Finegan, 2012/10/16 21:44:44]

This is what GetCdmVideoBufferImpl() calls, and that's why it was public. I've
made GetCdmVideoBufferImpl() a friend, and made it non-static (required to
friend it). This puts GetCdmVideoBufferImpl() in the webkit_media namespace,
while ReleaseCdmBufferImpl() remains static. Declaring the get and release
methods differently seems a little weird, but it should work.

Should I keep it this way, or change it back?

[ddorwin, 2012/10/17 03:18:20]

Go back. This causes you to friend and non-static the Impl method, so this is
worse. I forgot that FFmpeg doesn't use member functions.

[Tom Finegan, 2012/10/17 04:25:29]

Done.

+
+ private:
+  void ReleaseFFmpegResources();
+
+  // FFmpeg structures owned by this object.

[ddorwin, 2012/10/16 18:04:30]

Can we use scoped_ptr since these are owned? Or is that too much of base?

[Tom Finegan, 2012/10/16 21:44:44]

Discussed offline. Not really too much base, more that we need wrapper classes
for any FFmpeg objects that we want to put in scopers because we must pass
FFmpeg objects to av_free() instead of using delete.

[xhwang, 2012/10/17 18:43:00]

I miss boost::shared_ptr where you can specify deleters :)

+  AVCodecContext* codec_context_;
+  AVFrame* av_frame_;
+
+  cdm::Allocator* const allocator_;
+  cdm::VideoDecoderConfig config_;
+
+  DISALLOW_COPY_AND_ASSIGN(FFmpegCdmVideoDecoder);
+};
+
+}  // namespace webkit_media
+
+#endif  // WEBKIT_MEDIA_CRYPTO_PPAPI_FFMPEG_CDM_VIDEO_DECODER_H_