media: Add support for playback of VP8 Alpha video streams

media/filters/vpx_video_decoder.cc

Index: media/filters/vpx_video_decoder.cc
diff --git a/media/filters/vpx_video_decoder.cc b/media/filters/vpx_video_decoder.cc
index baab01741ab4a49bd3a02df5e400b0b80bbf0d12..c07c1b12ce381269996fbc720506eaca846396d3 100644
--- a/media/filters/vpx_video_decoder.cc
+++ b/media/filters/vpx_video_decoder.cc
@@ -11,6 +11,7 @@
 #include "base/logging.h"
 #include "base/message_loop_proxy.h"
 #include "base/string_number_conversions.h"
+#include "base/sys_byteorder.h"
 #include "media/base/bind_to_loop.h"
 #include "media/base/decoder_buffer.h"
 #include "media/base/demuxer_stream.h"
@@ -60,7 +61,8 @@ VpxVideoDecoder::VpxVideoDecoder(
     : message_loop_(message_loop),
       weak_factory_(this),
       state_(kUninitialized),
-      vpx_codec_(NULL) {
+      vpx_codec_(NULL),
+      vpx_codec_alpha_(NULL) {
 }
 
 VpxVideoDecoder::~VpxVideoDecoder() {
@@ -94,6 +96,28 @@ void VpxVideoDecoder::Initialize(
   status_cb.Run(PIPELINE_OK);
 }
 
+static vpx_codec_ctx* InitializeVpxContext(vpx_codec_ctx* context,
+                                           const VideoDecoderConfig& config) {
+  context = new vpx_codec_ctx();
+  vpx_codec_dec_cfg_t vpx_config = {0};
+  vpx_config.w = config.coded_size().width();
+  vpx_config.h = config.coded_size().height();
+  vpx_config.threads = GetThreadCount();
+
+  vpx_codec_err_t status = vpx_codec_dec_init(context,
+                                              config.codec() == kCodecVP9 ?
+                                                  vpx_codec_vp9_dx() :
+                                                  vpx_codec_vp8_dx(),
+                                              &vpx_config,
+                                              0);
+  if (status != VPX_CODEC_OK) {
+    LOG(ERROR) << "vpx_codec_dec_init failed, status=" << status;
+    delete context;
+    return NULL;
+  }
+  return context;
+}
+
 bool VpxVideoDecoder::ConfigureDecoder() {
   const VideoDecoderConfig& config = demuxer_stream_->video_decoder_config();
   if (!config.IsValidConfig()) {
@@ -102,26 +126,29 @@ bool VpxVideoDecoder::ConfigureDecoder() {
     return false;
   }
 
-  if (config.codec() != kCodecVP9)
+  const CommandLine* cmd_line = CommandLine::ForCurrentProcess();
+  bool can_handle = false;
+  if (cmd_line->HasSwitch(switches::kEnableVp9Playback) &&
+      config.codec() == kCodecVP9) {
+    can_handle = true;
+  }
+  if (cmd_line->HasSwitch(switches::kEnableVp8AlphaPlayback) &&
+      config.codec() == kCodecVP8 && config.format() == VideoFrame::YV12A) {
+    can_handle = true;
+  }
+  if (!can_handle)
     return false;
 
   CloseDecoder();
 
-  vpx_codec_ = new vpx_codec_ctx();
-  vpx_codec_dec_cfg_t vpx_config = {0};
-  vpx_config.w = config.coded_size().width();
-  vpx_config.h = config.coded_size().height();
-  vpx_config.threads = GetThreadCount();
-
-  vpx_codec_err_t status = vpx_codec_dec_init(vpx_codec_,
-                                              vpx_codec_vp9_dx(),
-                                              &vpx_config,
-                                              0);
-  if (status != VPX_CODEC_OK) {
-    LOG(ERROR) << "vpx_codec_dec_init failed, status=" << status;
-    delete vpx_codec_;
-    vpx_codec_ = NULL;
+  vpx_codec_ = InitializeVpxContext(vpx_codec_, config);
+  if (!vpx_codec_)
     return false;
+
+  if (config.format() == VideoFrame::YV12A) {
+    vpx_codec_alpha_ = InitializeVpxContext(vpx_codec_alpha_, config);
+    if (!vpx_codec_alpha_)
+      return false;
   }
 
   return true;
@@ -133,6 +160,11 @@ void VpxVideoDecoder::CloseDecoder() {
     delete vpx_codec_;
     vpx_codec_ = NULL;
   }
+  if (vpx_codec_alpha_) {
+    vpx_codec_destroy(vpx_codec_alpha_);
+    delete vpx_codec_alpha_;
+    vpx_codec_alpha_ = NULL;
+  }
 }
 
 void VpxVideoDecoder::Read(const ReadCB& read_cb) {
@@ -248,7 +280,7 @@ void VpxVideoDecoder::DecodeBuffer(
   }
 
   // Any successful decode counts!
-  if (buffer->GetDataSize()) {
+  if (buffer->GetDataSize() && buffer->GetSideDataSize()) {
     PipelineStatistics statistics;
     statistics.video_bytes_decoded = buffer->GetDataSize();
     statistics_cb_.Run(statistics);
@@ -295,7 +327,44 @@ bool VpxVideoDecoder::Decode(
     return false;
   }
 
-  CopyVpxImageTo(vpx_image, video_frame);
+  const vpx_image_t* vpx_image_alpha = NULL;
+  if (vpx_codec_alpha_ && buffer->GetSideDataSize() >= 8) {
+    // Pass alpha data to libvpx.
+    int64 timestamp_alpha = buffer->GetTimestamp().InMicroseconds();
+    void* user_priv_alpha = reinterpret_cast<void*>(&timestamp_alpha);
+
+    // First 8 bytes of side data is side_data_id in big endian.
+    const uint64 side_data_id = base::NetToHost64(
+        *(reinterpret_cast<const uint64*>(buffer->GetSideData())));
+    if (side_data_id == 1) {
+      status = vpx_codec_decode(vpx_codec_alpha_,
+                                buffer->GetSideData() + 8,
+                                buffer->GetSideDataSize() - 8,
+                                user_priv_alpha,
+                                0);
+
+      if (status != VPX_CODEC_OK) {
+        LOG(ERROR) << "vpx_codec_decode() failed on alpha, status=" << status;
+        return false;
+      }
+
+      // Gets pointer to decoded data.
+      vpx_codec_iter_t iter_alpha = NULL;
+      vpx_image_alpha = vpx_codec_get_frame(vpx_codec_alpha_, &iter_alpha);
+      if (!vpx_image_alpha) {
+        *video_frame = NULL;
+        return true;
+      }
+
+      if (vpx_image_alpha->user_priv !=
+          reinterpret_cast<void*>(&timestamp_alpha)) {
+        LOG(ERROR) << "Invalid output timestamp on alpha.";
+        return false;
+      }
+    }
+  }
+
+  CopyVpxImageTo(vpx_image, vpx_image_alpha, video_frame);
   (*video_frame)->SetTimestamp(base::TimeDelta::FromMicroseconds(timestamp));
   return true;
 }
@@ -310,6 +379,7 @@ void VpxVideoDecoder::DoReset() {
 
 void VpxVideoDecoder::CopyVpxImageTo(
     const vpx_image* vpx_image,
+    const struct vpx_image* vpx_image_alpha,
     scoped_refptr<VideoFrame>* video_frame) {
   CHECK(vpx_image);
   CHECK_EQ(vpx_image->d_w % 2, 0U);
@@ -321,11 +391,14 @@ void VpxVideoDecoder::CopyVpxImageTo(
   gfx::Size natural_size =
       demuxer_stream_->video_decoder_config().natural_size();
 
-  *video_frame = VideoFrame::CreateFrame(VideoFrame::YV12,
+  *video_frame = VideoFrame::CreateFrame(vpx_codec_alpha_ ?
+                                             VideoFrame::YV12A :
+                                             VideoFrame::YV12,
                                          size,
                                          gfx::Rect(size),
                                          natural_size,
                                          kNoTimestamp());
+
   CopyYPlane(vpx_image->planes[VPX_PLANE_Y],
              vpx_image->stride[VPX_PLANE_Y],
              vpx_image->d_h,
@@ -338,6 +411,17 @@ void VpxVideoDecoder::CopyVpxImageTo(
              vpx_image->stride[VPX_PLANE_V],
              vpx_image->d_h / 2,
              *video_frame);
+  if (!vpx_codec_alpha_)
+    return;
+  if (!vpx_image_alpha) {
+    MakeOpaqueAPlane(vpx_image->stride[VPX_PLANE_Y], vpx_image->d_h,
+                     *video_frame);
+    return;
+  }
+  CopyAPlane(vpx_image_alpha->planes[VPX_PLANE_Y],
+             vpx_image->stride[VPX_PLANE_Y],
+             vpx_image->d_h,
+             *video_frame);
 }
 
 }  // namespace media