Add 4k HW decode override flag and support larger bitstream buffers in V4L2VDA.

media/filters/gpu_video_decoder.cc

Index: media/filters/gpu_video_decoder.cc
diff --git a/media/filters/gpu_video_decoder.cc b/media/filters/gpu_video_decoder.cc
index 6842e4d7c59a4797c6c373f5916ad1c30feb357a..94bbd03b7f52cf12909a2300aa31c1ac8e4d9e31 100644
--- a/media/filters/gpu_video_decoder.cc
+++ b/media/filters/gpu_video_decoder.cc
@@ -8,6 +8,7 @@
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
+#include "base/command_line.h"
 #include "base/cpu.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
@@ -18,6 +19,7 @@
 #include "media/base/bind_to_current_loop.h"
 #include "media/base/decoder_buffer.h"
 #include "media/base/media_log.h"
+#include "media/base/media_switches.h"
 #include "media/base/pipeline.h"
 #include "media/base/pipeline_status.h"
 #include "media/base/video_decoder_config.h"
@@ -122,7 +124,9 @@ static bool IsCodedSizeSupported(const gfx::Size& coded_size) {
 
   base::CPU cpu;
   bool hw_large_video_support =
-      (cpu.vendor_name() == "GenuineIntel") && cpu.model() >= 55;
+      CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kForce4kAcceleratedVideoDecode) ||
+      ((cpu.vendor_name() == "GenuineIntel") && cpu.model() >= 55);

[piman, 2014/05/15 17:02:27]

Is this in the renderer?

What would happen if the renderer submits large videos anyway? Think malicious
renderer.

[Pawel Osciak, 2014/05/16 03:53:01]

This gates whether a HW or SW decoder is used. It's called after parsing the
container with the values from the container to decide if we can instantiate a
HW decoder to decode given stream. If not, we use a SW one.

If you mean a malicious stream that has invalid header information in the
container, then if it doesn't fit in the buffers, we check for that and fail if
we can't fit in the buffers. Such a case doesn't really differ much from a
stream that has any other invalid metadata in it.

   bool os_large_video_support = true;
 #if defined(OS_WIN)
   os_large_video_support = false;