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

content/common/gpu/media/v4l2_video_decode_accelerator.h

 // Copyright 2014 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.
 //
 // This file contains an implementation of VideoDecodeAccelerator
 // that utilizes hardware video decoders, which expose Video4Linux 2 API
 // (http://linuxtv.org/downloads/v4l-dvb-apis/).
 
 #ifndef CONTENT_COMMON_GPU_MEDIA_V4L2_VIDEO_DECODE_ACCELERATOR_H_
 #define CONTENT_COMMON_GPU_MEDIA_V4L2_VIDEO_DECODE_ACCELERATOR_H_
@@ skipping 87 matching lines @@
 
   // VideoDecodeAcceleratorImpl implementation.
   virtual bool CanDecodeOnIOThread() OVERRIDE;
 
  private:
   // These are rather subjectively tuned.
   enum {
     kInputBufferCount = 8,
     // TODO(posciak): determine input buffer size based on level limits.
     // See http://crbug.com/255116.
-    kInputBufferMaxSize = 1024 * 1024,
+    kInputBufferMaxSize = 4 * 1024 * 1024,

[Ami GONE FROM CHROMIUM, 2014/05/15 16:00:42]

CL description made me expect this to be conditional on the switch (would
require not being a compile-time constant anymore, obvs).  I don't feel strongly
about this, but I am sad at wasting 16MB shm per <video> :(

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

I'm uncomfortable making this remote relationship between
GVD::IsCodedSizeSupported and V4L2VDA buffer size.
I agree it would be good to save that memory though. Ideally we should be using
the same code as GVD::ICSS() in V4L2VDA
to decide which buffer size to use instead of hardcoding this. I'm not sure if
it's a good idea to cross-call GVD from V4L2VDA like this though, and moving
ICSS to VDA would have to go to the base class...

[Ami GONE FROM CHROMIUM, 2014/05/16 16:49:59]

...as opposed to the current "remote relationship" between the magic number of
2MB in V4L2VDA and GVD::ICSS enforcing that nothing that might break that shows
up here?

I don't think that what I'm proposing makes the coupling any stronger than it
already is, and it will save a bunch of memory, so I think it's worthwhile.

     // Number of output buffers to use for each VDA stage above what's required
     // by the decoder (e.g. DPB size, in H264).  We need
     // media::limits::kMaxVideoFrames to fill up the GpuVideoDecode pipeline,
     // and +1 for a frame in transit.
     kDpbOutputBufferExtraCount = media::limits::kMaxVideoFrames + 1,
   };
 
   // Internal state of the decoder.
   enum State {
     kUninitialized,      // Initialize() not yet called.
@@ skipping 317 matching lines @@
 
   // The WeakPtrFactory for |weak_this_|.
   base::WeakPtrFactory<V4L2VideoDecodeAccelerator> weak_this_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(V4L2VideoDecodeAccelerator);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_GPU_MEDIA_V4L2_VIDEO_DECODE_ACCELERATOR_H_