Clarify resolution change behaviors of video capture devices

media/video/capture/video_capture_types.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 MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_TYPES_H_
 #define MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_TYPES_H_
 
 #include <vector>
 
 #include "media/base/media_export.h"
@@ skipping 13 matching lines @@
   PIXEL_FORMAT_UYVY,
   PIXEL_FORMAT_RGB24,
   PIXEL_FORMAT_ARGB,
   PIXEL_FORMAT_MJPEG,
   PIXEL_FORMAT_NV21,
   PIXEL_FORMAT_YV12,
   PIXEL_FORMAT_TEXTURE,  // Capture format as a GL texture.
   PIXEL_FORMAT_MAX,
 };
 
+// Policies for capture devices that has source content with dynamic resolution.
+enum ResolutionChangePolicy {
+  // Capture device outputs a fixed resolution all the time. The resolution of
+  // the first frame is the resolution for all frames.
+  // It is implementation specific for the capture device to scale, letter-box
+  // and pillar-box. The only gurantee is that resolution will never change.

[mcasas, 2014/09/08 09:09:53]

s/gurantee/guarantee/

+  RESOLUTION_POLICY_FIXED,
+
+  // Capture device outputs frames with dynamic resolution. The width and height
+  // will not exceed the maximum dimensions specified. The typical scenario is
+  // the frames will have the same aspect ratio as the original content and
+  // scaled down to fit inside the limit.
+  RESOLUTION_POLICY_DYNAMIC_WITHIN_LIMIT,
+
+  RESOLUTION_POLICY_LAST,
+};
+
 // Some drivers use rational time per frame instead of float frame rate, this
 // constant k is used to convert between both: A fps -> [k/k*A] seconds/frame.
 const int kFrameRatePrecision = 10000;
 
 // Video capture format specification.
 // This class is used by the video capture device to specify the format of every
 // frame captured and returned to a client. It is also used to specify a
 // supported capture format by a device.
 class MEDIA_EXPORT VideoCaptureFormat {
  public:
@@ skipping 19 matching lines @@
 // This class is used by the client of a video capture device to specify the
 // format of frames in which the client would like to have captured frames
 // returned.
 class MEDIA_EXPORT VideoCaptureParams {
  public:
   VideoCaptureParams();
 
   // Requests a resolution and format at which the capture will occur.
   VideoCaptureFormat requested_format;
 
-  // Allow mid-capture resolution change.
-  bool allow_resolution_change;
+  // Policy for resolution change.
+  ResolutionChangePolicy resolution_change_policy;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_TYPES_H_