Implement software fallback for PPB_VideoDecoder.

ppapi/examples/video_decode/video_decode.cc

Index: ppapi/examples/video_decode/video_decode.cc
diff --git a/ppapi/examples/video_decode/video_decode.cc b/ppapi/examples/video_decode/video_decode.cc
index de9bb8df2c0c417ecb1c1a45cf5a4e2a58ec10e0..f379d0497db704bcc5eb79e906884b7c377dc379 100644
--- a/ppapi/examples/video_decode/video_decode.cc
+++ b/ppapi/examples/video_decode/video_decode.cc
@@ -20,7 +20,12 @@
 #include "ppapi/cpp/rect.h"
 #include "ppapi/cpp/var.h"
 #include "ppapi/cpp/video_decoder.h"
+
+// One of these should be defined.
+//#define TEST_H264
+#define TEST_VP8

[Ami GONE FROM CHROMIUM, 2014/06/05 00:06:24]

If you made these USE_VP8_TESTDATA_INSTEAD_OF_H264 then:
- you wouldn't have to edit the _dev.cc example
- you wouldn't risk someone defining both, which is invalid
- you woulnd't risk colliding with far-flung defines from other places since
nobody in their right mind would use such an unwieldy macro name.

[bbudge, 2014/06/06 02:03:45]

I like it. Done.

 #include "ppapi/examples/video_decode/testdata.h"
+
 #include "ppapi/lib/gl/include/GLES2/gl2.h"
 #include "ppapi/lib/gl/include/GLES2/gl2ext.h"
 #include "ppapi/utility/completion_callback_factory.h"
@@ -56,6 +61,7 @@ class MyInstance : public pp::Instance, public pp::Graphics3DClient {
   // pp::Instance implementation.
   virtual void DidChangeView(const pp::Rect& position,
                              const pp::Rect& clip_ignored);
+  virtual bool HandleInputEvent(const pp::InputEvent& event);
 
   // pp::Graphics3DClient implementation.
   virtual void Graphics3DContextLost() {
@@ -139,12 +145,12 @@ class Decoder {
   int id() const { return id_; }
   bool decoding() const { return !flushing_ && !resetting_; }
 
-  void Seek(int frame);
+  void Reset();
   void RecyclePicture(const PP_VideoPicture& picture);
 
  private:
   void InitializeDone(int32_t result);
-  void Start(int frame);
+  void Start();
   void DecodeNextFrame();
   void DecodeDone(int32_t result);
   void PictureReady(int32_t result, PP_VideoPicture picture);
@@ -159,11 +165,12 @@ class Decoder {
 
   size_t encoded_data_next_pos_to_decode_;
   int next_picture_id_;
-  int seek_frame_;
   bool flushing_;
   bool resetting_;
 };
 
+#if defined(TEST_H264)
+
 // Returns true if the current position is at the start of a NAL unit.
 static bool LookingAtNAL(const unsigned char* encoded, size_t pos) {
   // H264 frames start with 0, 0, 0, 1 in our test data.
@@ -171,7 +178,6 @@ static bool LookingAtNAL(const unsigned char* encoded, size_t pos) {
          encoded[pos + 2] == 0 && encoded[pos + 3] == 1;
 }
 
-// Find the start and end of the next frame.
 static void GetNextFrame(size_t* start_pos, size_t* end_pos) {
   assert(LookingAtNAL(kData, *start_pos));
   *end_pos = *start_pos;
@@ -181,6 +187,23 @@ static void GetNextFrame(size_t* start_pos, size_t* end_pos) {
   }
 }
 
+#elif defined(TEST_VP8)  // VP8
+
+// VP8 is stored in an IVF container.
+// Helpful description: http://wiki.multimedia.cx/index.php?title=IVF
+
+static void GetNextFrame(size_t* start_pos, size_t* end_pos) {
+  size_t current_pos = *start_pos;
+  if (current_pos == 0)
+    current_pos = 32;  // Skip stream header.
+  uint32_t frame_size = *reinterpret_cast<const uint32_t*>(&kData[current_pos]);

[Ami GONE FROM CHROMIUM, 2014/06/05 00:06:24]

This is a type-punning violation; please see base/macros.h:bit_cast's commentary
for a description of the problem.
You probably just want to construct the uint32 with bit-shifts and addition,
instead of replicating bit_cast's memcpy strategy.

[bbudge, 2014/06/06 02:03:45]

Done.

+  current_pos += 12;  // Skip frame header.
+  *start_pos = current_pos;
+  *end_pos = current_pos + frame_size;
+}
+
+#endif

[Ami GONE FROM CHROMIUM, 2014/06/05 00:06:24]

#else
#error Oops!

unless you take my suggestion above.

[bbudge, 2014/06/06 02:03:45]

Done.

+
 Decoder::Decoder(MyInstance* instance,
                  int id,
                  const pp::Graphics3D& graphics_3d)
@@ -190,14 +213,18 @@ Decoder::Decoder(MyInstance* instance,
       callback_factory_(this),
       encoded_data_next_pos_to_decode_(0),
       next_picture_id_(0),
-      seek_frame_(0),
       flushing_(false),
       resetting_(false) {
   assert(!decoder_->is_null());
-  const PP_VideoProfile profile = PP_VIDEOPROFILE_H264MAIN;
+  const PP_VideoProfile profile =
+#if defined(TEST_H264)
+      PP_VIDEOPROFILE_H264MAIN;

[Ami GONE FROM CHROMIUM, 2014/06/05 00:06:24]

This should probably be part of the header file alongside its data.

[bbudge, 2014/06/06 02:03:46]

Done.

+#elif defined(TEST_VP8)
+      PP_VIDEOPROFILE_VP8MAIN;
+#endif
   decoder_->Initialize(graphics_3d,
                        profile,
-                       PP_FALSE /* allow_software_fallback */,
+                       PP_TRUE /* allow_software_fallback */,
                        callback_factory_.NewCallback(&Decoder::InitializeDone));
 }
 
@@ -209,18 +236,13 @@ void Decoder::InitializeDone(int32_t result) {
   assert(decoder_);
   assert(result == PP_OK);
   assert(decoding());
-  Start(0);
+  Start();
 }
 
-void Decoder::Start(int frame) {
+void Decoder::Start() {
   assert(decoder_);
 
-  // Skip to |frame|.
-  size_t start_pos = 0;
-  size_t end_pos = 0;
-  for (int i = 0; i < frame; i++)
-    GetNextFrame(&start_pos, &end_pos);
-  encoded_data_next_pos_to_decode_ = end_pos;
+  encoded_data_next_pos_to_decode_ = 0;
 
   // Register callback to get the first picture. We call GetPicture again in
   // PictureReady to continuously receive pictures as they're decoded.
@@ -231,9 +253,8 @@ void Decoder::Start(int frame) {
   DecodeNextFrame();
 }
 
-void Decoder::Seek(int frame) {
+void Decoder::Reset() {
   assert(decoder_);
-  seek_frame_ = frame;
   resetting_ = true;
   decoder_->Reset(callback_factory_.NewCallback(&Decoder::ResetDone));
 }
@@ -299,6 +320,8 @@ void Decoder::ResetDone(int32_t result) {
   assert(decoder_);
   assert(result == PP_OK);
   resetting_ = false;
+
+  Start();
 }
 
 MyInstance::MyInstance(PP_Instance instance, pp::Module* module)
@@ -353,6 +376,23 @@ void MyInstance::DidChangeView(const pp::Rect& position,
   InitializeDecoders();
 }
 
+bool MyInstance::HandleInputEvent(const pp::InputEvent& event) {
+  switch (event.GetType()) {
+    case PP_INPUTEVENT_TYPE_MOUSEDOWN: {
+      pp::MouseInputEvent mouse_event(event);
+      // Reset all decoders on mouse down.
+      if (mouse_event.GetButton() == PP_INPUTEVENT_MOUSEBUTTON_LEFT) {
+        for (size_t i = 0; i < video_decoders_.size(); i++)
+          video_decoders_[i]->Reset();

[Ami GONE FROM CHROMIUM, 2014/06/05 00:06:24]

I'm surprised you don't end up having to pause/cancel any other things like
decode or pictureready waiting.

[bbudge, 2014/06/06 02:03:46]

The example won't call Decode after Reset, since any completed Decodes are
aborted after that.

I did play with clearing pending paints. That causes one decoder to hang. I
think it's because of the way the example paints. It brings up an interesting
question: Are any textures the plugin holds valid after Reset? Looking at the
implementation, the textures are implicitly recycled back to the proxy, but they
remain valid for rendering until the plugin starts calling Decode again.

+      }
+      return true;
+    }
+
+    default:
+      return false;
+  }
+}
+
 void MyInstance::InitializeDecoders() {
   assert(video_decoders_.empty());
   // Create two decoders with ids 0 and 1.