1 Name 2 3 ANDROID_recordable 4 5 Name Strings 6 7 EGL_ANDROID_recordable 8 9 Contributors 10 11 Jamie Gennis 12 13 Contact 14 15 Jamie Gennis, Google Inc. (jgennis 'at' google.com) 16 17 Status 18 19 Draft. 20 21 Version 22 23 Version 1, July 8, 2011 24 25 Number 26 27 EGL Extension #XXX 28 29 Dependencies 30 31 Requires EGL 1.0 32 33 This extension is written against the wording of the EGL 1.4 Specification 34 35 Overview 36 37 Android supports a number of different ANativeWindow implementations that 38 can be used to create an EGLSurface. One implementation, which records the 39 rendered image as a video each time eglSwapBuffers gets called, may have 40 some device-specific restrictions. Because of this, some EGLConfigs may be 41 incompatible with these ANativeWindows. This extension introduces a new 42 boolean EGLConfig attribute that indicates whether the EGLConfig supports 43 rendering to an ANativeWindow that records images to a video. 44 45 New Types 46 47 None. 48 49 New Procedures and Functions 50 51 None. 52 53 New Tokens 54 55 Accepted by the <attribute> parameter of eglGetConfigAttrib and 56 the <attrib_list> parameter of eglChooseConfig: 57 58 EGL_RECORDABLE_ANDROID 0x3142 59 60 Changes to Chapter 3 of the EGL 1.4 Specification (EGL Functions and Errors) 61 62 Section 3.4, Configuration Management, add a row to Table 3.1. 63 64 Attribute Type Notes 65 ---------------------- ------- -------------------------- 66 EGL_RECORDABLE_ANDROID boolean whether video recording is 67 supported 68 69 Section 3.4, Configuration Management, add a row to Table 3.4. 70 71 Attribute Default Selection Sort Sort 72 Criteria Order Priority 73 ---------------------- ------------- --------- ----- -------- 74 EGL_RECORDABLE_ANDROID EGL_DONT_CARE Exact None 75 76 Section 3.4, Configuration Management, add a paragraph at the end of the 77 subsection titled Other EGLConfig Attribute Descriptions. 78 79 EGL_RECORDABLE_ANDROID is a boolean indicating whether the config may 80 be used to create an EGLSurface from an ANativeWindow that is a video 81 recorder as indicated by the NATIVE_WINDOW_IS_VIDEO_RECORDER query on 82 the ANativeWindow. 83 84 Section 3.4.1, Querying Configurations, change the last paragraph as follow 85 86 EGLConfigs are not sorted with respect to the parameters 87 EGL_BIND_TO_TEXTURE_RGB, EGL_BIND_TO_TEXTURE_RGBA, EGL_CONFORMANT, 88 EGL_LEVEL, EGL_NATIVE_RENDERABLE, EGL_MAX_SWAP_INTERVAL, 89 EGL_MIN_SWAP_INTERVAL, EGL_RENDERABLE_TYPE, EGL_SURFACE_TYPE, 90 EGL_TRANSPARENT_TYPE, EGL_TRANSPARENT_RED_VALUE, 91 EGL_TRANSPARENT_GREEN_VALUE, EGL_TRANSPARENT_BLUE_VALUE, and 92 EGL_RECORDABLE_ANDROID. 93 94 Issues 95 96 1. Should this functionality be exposed as a new attribute or as a bit in 97 the EGL_SURFACE_TYPE bitfield? 98 99 RESOLVED: It should be a new attribute. It does not make sense to use up a 100 bit in the limit-size bitfield for a platform-specific extension. 101 102 2. How should the new attribute affect the sorting of EGLConfigs? 103 104 RESOLVED: It should not affect sorting. Some implementations may not have 105 any drawback associated with using a recordable EGLConfig. Such 106 implementations should not have to double-up some of their configs to one 107 sort earlier than . Implementations that do have drawbacks can use the 108 existing caveat mechanism to report this drawback to the client. 109 110 3. How is this extension expected to be implemented? 111 112 RESPONSE: There are two basic approaches to implementing this extension 113 that were considered during its design. In both cases it is assumed that a 114 color space conversion must be performed at some point because most video 115 encoding formats use a YUV color space. The two approaches are 116 distinguished by the point at which this color space conversion is 117 performed. 118 119 One approach involves performing the color space conversion as part of the 120 eglSwapBuffers call before queuing the rendered image to the ANativeWindow. 121 In this case, the VisualID of the EGLConfig would correspond to a YUV 122 Android HAL pixel format from which the video encoder can read. The 123 EGLConfig would likely have the EGL_SLOW_CONFIG caveat because using that 124 config to render normal window contents would result in an RGB -> YUV color 125 space conversion when rendering the frame as well as a YUV -> RGB 126 conversion when compositing the window. 127 128 The other approach involves performing the color space conversion in the 129 video encoder. In this case, the VisualID of the EGLConfig would 130 correspond to an RGB HAL pixel format from which the video encoder can 131 read. The EGLConfig would likely not need to have any caveat set, as using 132 this config for normal window rendering would not have any added cost. 133 134 Revision History 135 136 #2 (Jamie Gennis, July 15, 2011) 137 - Added issue 3. 138 139 #1 (Jamie Gennis, July 8, 2011) 140 - Initial draft. 141
