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// Copyright 2016 The Cobalt Authors. All Rights Reserved.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
// Module Overview: Starboard Decode Target module
// A target for decoding image and video data into. This corresponds roughly to
// an EGLImage, but that extension may not be fully supported on all GL
// platforms. SbDecodeTarget supports multi-plane targets. The SbBlitter API is
// supported as well, and this is able to more-or-less unify the two.
// An SbDecodeTarget can be passed into any function which decodes video or
// image data. This allows the application to allocate fast graphics memory, and
// have decoding done directly into this memory, avoiding unnecessary memory
// copies, and also avoiding pushing data between CPU and GPU memory
// unnecessarily.
// # SbDecodeTargetFormat
// SbDecodeTargets support several different formats that can be used to decode
// into and render from. Some formats may be easier to decode into, and others
// may be easier to render. Some may take less memory. Each decoder needs to
// support the SbDecodeTargetFormat passed into it, or the decode will produce
// an error. Each decoder provides a way to check if a given
// SbDecodeTargetFormat is supported by that decoder.
// # SbDecodeTargetGraphicsContextProvider
// Some components may need to acquire SbDecodeTargets compatible with a certain
// rendering context, which may need to be created on a particular thread. The
// SbDecodeTargetGraphicsContextProvider are passed in to the Starboard
// implementation from the application and provide information about the
// rendering context that will be used to render the SbDecodeTarget objects.
// For GLES renderers, it also provides functionality to enable the Starboard
// implementation to run arbitrary code on the application's renderer thread
// with the renderer's EGLContext held current. This may be useful if your
// SbDecodeTarget creation code needs to execute GLES commands like, for
// example, glGenTextures().
// The primary usage is likely to be the the SbPlayer implementation on some
// platforms.
// # SbDecodeTarget Example
// Let's say that we are an application and we would like to use the interface
// defined in starboard/image.h to decode an imaginary "image/foo" image type.
// First, the application should enumerate which SbDecodeTargetFormats are
// supported by that decoder.
// SbDecodeTargetFormat kPreferredFormats[] = {
// kSbDecodeTargetFormat3PlaneYUVI420,
// kSbDecodeTargetFormat1PlaneRGBA,
// kSbDecodeTargetFormat1PlaneBGRA,
// };
// SbDecodeTargetFormat format = kSbDecodeTargetFormatInvalid;
// for (int i = 0; i < SB_ARRAY_SIZE_INT(kPreferredFormats); ++i) {
// if (SbImageIsDecodeSupported("image/foo", kPreferredFormats[i])) {
// format = kPreferredFormats[i];
// break;
// }
// }
// Now that the application has a format, it can create a decode target that it
// will use to decode the .foo file into. Let's assume format is
// kSbDecodeTargetFormat1PlaneRGBA, that we are on an EGL/GLES2 platform.
// Also, we won't do any error checking, to keep things even simpler.
// SbDecodeTarget target = SbImageDecode(
// context_provider, encoded_foo_data, encoded_foo_data_size,
// "image/foo", format);
// // If the decode works, you can get the texture out and render it.
// SbDecodeTargetInfo info;
// memset(&info, 0, sizeof(info));
// SbDecodeTargetGetInfo(target, &info);
// GLuint texture =
// info.planes[kSbDecodeTargetPlaneRGBA].texture;
#include "starboard/common/log.h"
#include "starboard/configuration.h"
#include "starboard/export.h"
#include "starboard/types.h"
#include "starboard/blitter.h"
#endif // SB_API_VERSION < 12 && SB_HAS(BLITTER)
#ifdef __cplusplus
extern "C" {
// --- Types -----------------------------------------------------------------
// Private structure representing a target for image data decoding.
typedef struct SbDecodeTargetPrivate SbDecodeTargetPrivate;
// A handle to a target for image data decoding.
typedef SbDecodeTargetPrivate* SbDecodeTarget;
// The list of all possible decoder target formats. An SbDecodeTarget consists
// of one or more planes of data, each plane corresponding with a surface. For
// some formats, different planes will be different sizes for the same
// dimensions.
// NOTE: For enumeration entries with an alpha component, the alpha will always
// be premultiplied unless otherwise explicitly specified.
typedef enum SbDecodeTargetFormat {
// A decoder target format consisting of a single RGBA plane, in that channel
// order.
// A decoder target format consisting of a single BGRA plane, in that channel
// order.
// A decoder target format consisting of Y and interleaved UV planes, in that
// plane and channel order.
// A decoder target format consisting of Y, U, and V planes, in that order.
// A decoder target format consisting of 10bit Y, U, and V planes, in that
// order.
// A decoder target format consisting of a single plane with pixels laid out
// in the format UYVY. Since there are two Y values per sample, but only one
// U value and only one V value, horizontally the Y resolution is twice the
// size of both the U and V resolutions. Vertically, they Y, U and V all
// have the same resolution. This is a YUV 422 format. When using this
// format with GL platforms, it is expected that the underlying texture will
// be set to the GL_RGBA format, and the width of the texture will be equal to
// the number of UYVY tuples per row (e.g. the u/v width resolution).
// Content region left/right should be specified in u/v width resolution.
// An invalid decode target format.
} SbDecodeTargetFormat;
// All the planes supported by SbDecodeTarget.
typedef enum SbDecodeTargetPlane {
// The RGBA plane for the RGBA format.
kSbDecodeTargetPlaneRGBA = 0,
// The BGRA plane for the BGRA format.
kSbDecodeTargetPlaneBGRA = 0,
// The Y plane for multi-plane YUV formats.
kSbDecodeTargetPlaneY = 0,
// The UV plane for 2-plane YUV formats.
kSbDecodeTargetPlaneUV = 1,
// The U plane for 3-plane YUV formats.
kSbDecodeTargetPlaneU = 1,
// The V plane for 3-plane YUV formats.
kSbDecodeTargetPlaneV = 2,
} SbDecodeTargetPlane;
struct SbDecodeTargetGraphicsContextProvider;
// Signature for a Starboard implementation function that is to be run by a
// SbDecodeTargetGlesContextRunner callback.
typedef void (*SbDecodeTargetGlesContextRunnerTarget)(
void* gles_context_runner_target_context);
// Signature for a function provided by the application to the Starboard
// implementation that will let the Starboard implementation run arbitrary code
// on the application's renderer thread with the application's EGLContext held
// current.
typedef void (*SbDecodeTargetGlesContextRunner)(
struct SbDecodeTargetGraphicsContextProvider* graphics_context_provider,
SbDecodeTargetGlesContextRunnerTarget target_function,
void* target_function_context);
#endif // SB_API_VERSION >= 12 || SB_HAS(GLES2)
// In general, the SbDecodeTargetGraphicsContextProvider structure provides
// information about the graphics context that will be used to render
// SbDecodeTargets. Some Starboard implementations may need to have references
// to some graphics objects when creating/destroying resources used by
// SbDecodeTarget. References to SbDecodeTargetGraphicsContextProvider objects
// should be provided to all Starboard functions that might create
// SbDecodeTargets (e.g. SbImageDecode()).
typedef struct SbDecodeTargetGraphicsContextProvider {
// The SbBlitterDevice object that will be used to render any produced
// SbDecodeTargets.
SbBlitterDevice device;
// A reference to the EGLDisplay object that hosts the EGLContext that will
// be used to render any produced SbDecodeTargets. Note that it has the
// type |void*| in order to avoid #including the EGL header files here.
void* egl_display;
// The EGLContext object that will be used to render any produced
// SbDecodeTargets. Note that it has the
// type |void*| in order to avoid #including the EGL header files here.
void* egl_context;
// The |gles_context_runner| function pointer is passed in from the
// application into the Starboard implementation, and can be invoked by the
// Starboard implementation to allow running arbitrary code on the renderer's
// thread with the EGLContext above held current.
SbDecodeTargetGlesContextRunner gles_context_runner;
// Context data that is to be passed in to |gles_context_runner| when it is
// invoked.
void* gles_context_runner_context;
#elif !(SB_API_VERSION >= 12 || SB_HAS(BLITTER))
// Some compilers complain about empty structures, this is to appease them.
char dummy;
#endif // SB_API_VERSION >= 12 || SB_HAS(GLES2)
} SbDecodeTargetGraphicsContextProvider;
// Defines a rectangular content region within a SbDecodeTargetInfoPlane
// structure.
typedef struct SbDecodeTargetInfoContentRegion {
// If the texture (width, height) is set to (1, 1), then these values will
// be interpreted as normalized coordinates, and depending on the platform
// (for example GLES 2.0 provides no method of obtaining the texture
// width/height) this may be more natural than specifying absolute pixel
// offsets.
float left;
float top;
float right;
float bottom;
} SbDecodeTargetInfoContentRegion;
// Defines an image plane within a SbDecodeTargetInfo object.
typedef struct SbDecodeTargetInfoPlane {
// A handle to the Blitter surface that can be used for rendering.
SbBlitterSurface surface;
#endif // SB_API_VERSION < 12 && SB_HAS(BLITTER)
// A handle to the GL texture that can be used for rendering.
uint32_t texture;
// The GL texture target that should be used in calls to glBindTexture.
// Typically this would be GL_TEXTURE_2D, but some platforms may require
// that it be set to something else like GL_TEXTURE_EXTERNAL_OES.
uint32_t gl_texture_target;
// For kSbDecodeTargetFormat2PlaneYUVNV12 planes: the format of the
// texture. Usually, for the luma plane, this is either GL_ALPHA or
// GL_RED_EXT. For the chroma plane, this is usually GL_LUMINANCE_ALPHA
// or GL_RG_EXT.
// Ignored for other plane types.
uint32_t gl_texture_format;
#endif // SB_API_VERSION >= 12 || SB_HAS(GLES2)
// The width of the texture/surface for this particular plane.
int width;
// The height of the texture/surface for this particular plane.
int height;
// The following properties specify a rectangle indicating a region within
// the texture/surface that contains valid image data. The top-left corner
// is (0, 0) and increases to the right and to the bottom. The units
// specified by these parameters are number of pixels. The range for
// left/right is [0, width], and for top/bottom it is [0, height].
SbDecodeTargetInfoContentRegion content_region;
} SbDecodeTargetInfoPlane;
// Contains all information about a decode target, including all of its planes.
// This can be queried via calls to SbDecodeTargetGetInfo().
typedef struct SbDecodeTargetInfo {
// The decode target format, which would dictate how many planes can be
// expected in |planes|.
SbDecodeTargetFormat format;
// Specifies whether the decode target is opaque. The underlying
// source of this value is expected to be properly maintained by the Starboard
// implementation. So, for example, if an opaque only image type were decoded
// into an SbDecodeTarget, then the implementation would configure things in
// such a way that this value is set to true. By opaque, it is meant
// that all alpha values are guaranteed to be 255, if the decode target is of
// a format that has alpha values. If the decode target is of a format that
// does not have alpha values, then this value should be set to true.
// Applications may rely on this value in order to implement certain
// optimizations such as occlusion culling.
bool is_opaque;
// The width of the image represented by this decode target.
int width;
// The height of the image represented by this decode target.
int height;
// The image planes (e.g. kSbDecodeTargetPlaneRGBA, or {kSbDecodeTargetPlaneY,
// kSbDecodeTargetPlaneU, kSbDecodeTargetPlaneV} associated with this
// decode target.
SbDecodeTargetInfoPlane planes[3];
} SbDecodeTargetInfo;
// --- Constants -------------------------------------------------------------
// Well-defined value for an invalid decode target handle.
#define kSbDecodeTargetInvalid ((SbDecodeTarget)NULL)
// --- Functions -------------------------------------------------------------
// Returns whether the given file handle is valid.
static SB_C_INLINE bool SbDecodeTargetIsValid(SbDecodeTarget handle) {
return handle != kSbDecodeTargetInvalid;
// Returns whether a given format is valid.
static SB_C_INLINE bool SbDecodeTargetIsFormatValid(
SbDecodeTargetFormat format) {
return format != kSbDecodeTargetFormatInvalid;
static SB_C_INLINE int SbDecodeTargetNumberOfPlanesForFormat(
SbDecodeTargetFormat format) {
switch (format) {
case kSbDecodeTargetFormat1PlaneRGBA:
case kSbDecodeTargetFormat1PlaneUYVY:
return 1;
case kSbDecodeTargetFormat1PlaneBGRA:
return 1;
case kSbDecodeTargetFormat2PlaneYUVNV12:
return 2;
case kSbDecodeTargetFormat3Plane10BitYUVI420:
case kSbDecodeTargetFormat3PlaneYUVI420:
return 3;
return 0;
// Returns ownership of |decode_target| to the Starboard implementation.
// This function will likely result in the destruction of the SbDecodeTarget and
// all its associated surfaces, though in some cases, platforms may simply
// adjust a reference count. In the case where SB_HAS(GLES2), this function
// must be called on a thread with the context
SB_EXPORT void SbDecodeTargetRelease(SbDecodeTarget decode_target);
// Writes all information about |decode_target| into |out_info|. Returns false
// if the provided |out_info| structure is not zero initialized.
SB_EXPORT bool SbDecodeTargetGetInfo(SbDecodeTarget decode_target,
SbDecodeTargetInfo* out_info);
// Inline convenience function to run an arbitrary
// SbDecodeTargetGlesContextRunnerTarget function through a
// SbDecodeTargetGraphicsContextProvider. This is intended to be called by
// Starboard implementations, if it is necessary.
static SB_C_INLINE void SbDecodeTargetRunInGlesContext(
SbDecodeTargetGraphicsContextProvider* provider,
SbDecodeTargetGlesContextRunnerTarget target,
void* target_context) {
provider->gles_context_runner(provider, target, target_context);
// This function is just an implementation detail of
// SbDecodeTargetReleaseInGlesContext() and should not be called directly.
static SB_C_INLINE void PrivateDecodeTargetReleaser(void* context) {
SbDecodeTarget decode_target = (SbDecodeTarget)context;
// Helper function that is possibly useful to Starboard implementations that
// will release a decode target on the thread with the GLES context current.
static SB_C_INLINE void SbDecodeTargetReleaseInGlesContext(
SbDecodeTargetGraphicsContextProvider* provider,
SbDecodeTarget decode_target) {
SbDecodeTargetRunInGlesContext(provider, &PrivateDecodeTargetReleaser,
#endif // SB_HAS(GLES2)
#ifdef __cplusplus
} // extern "C"