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.
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.
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.
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; SbMemorySet(&info, 0, sizeof(info)); SbDecodeTargetGetInfo(target, &info); GLuint texture = info.planes[kSbDecodeTargetPlaneRGBA].texture;
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.
Values
kSbDecodeTargetFormat1PlaneRGBA - A decoder target format consisting of a single RGBA plane, in that channelorder.kSbDecodeTargetFormat1PlaneBGRA - A decoder target format consisting of a single BGRA plane, in that channelorder.kSbDecodeTargetFormat2PlaneYUVNV12 - A decoder target format consisting of Y and interleaved UV planes, in thatplane and channel order.kSbDecodeTargetFormat3PlaneYUVI420 - A decoder target format consisting of Y, U, and V planes, in that order.kSbDecodeTargetFormat1PlaneUYVY - A decoder target format consisting of a single plane with pixels layed outin the format UYVY. Since there are two Y values per sample, but only oneU value and only one V value, horizontally the Y resolution is twice thesize of both the U and V resolutions. Vertically, they Y, U and V allhave the same resolution. This is a YUV 422 format. When using thisformat with GL platforms, it is expected that the underlying texture willbe set to the GL_RGBA format, and the width of the texture will be equal tothe 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.kSbDecodeTargetFormatInvalid - An invalid decode target format.All the planes supported by SbDecodeTarget.
Values
kSbDecodeTargetPlaneRGBA - The RGBA plane for the RGBA format.kSbDecodeTargetPlaneBGRA - The BGRA plane for the BGRA format.kSbDecodeTargetPlaneY - The Y plane for multi-plane YUV formats.kSbDecodeTargetPlaneUV - The UV plane for 2-plane YUV formats.kSbDecodeTargetPlaneU - The U plane for 3-plane YUV formats.kSbDecodeTargetPlaneV - The V plane for 3-plane YUV formats.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()).
Members
Contains all information about a decode target, including all of its planes. This can be queried via calls to SbDecodeTargetGetInfo().
Members
Defines a rectangular content region within a SbDecodeTargetInfoPlane structure.
Members
Defines an image plane within a SbDecodeTargetInfo object.
Members
Private structure representing a target for image data decoding.
Description
This function is just an implementation detail of SbDecodeTargetReleaseInGlesContext() and should not be called directly.
Declaration
static SB_C_INLINE void PrivateDecodeTargetReleaser(void* context) {
SbDecodeTarget decode_target = (SbDecodeTarget)context;
SbDecodeTargetRelease(decode_target);
}
Parameters
Description
Writes all information about decode_target into out_info. Returns false if the provided out_info structure is not zero initialized.
Declaration and definitions
#include "starboard/decode_target.h"
bool SbDecodeTargetGetInfo(SbDecodeTarget /*decode_target*/,
SbDecodeTargetInfo* /*out_info*/) {
return false;
}
Parameters
Description
Returns whether a given format is valid.
Declaration
static SB_C_INLINE bool SbDecodeTargetIsFormatValid(
SbDecodeTargetFormat format) {
return format != kSbDecodeTargetFormatInvalid;
}
Parameters
Description
Returns whether the given file handle is valid.
Declaration
static SB_C_INLINE bool SbDecodeTargetIsValid(SbDecodeTarget handle) {
return handle != kSbDecodeTargetInvalid;
}
Parameters
Declaration
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 kSbDecodeTargetFormat3PlaneYUVI420:
return 3;
default:
SB_NOTREACHED();
return 0;
}
}
Parameters
Description
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
Declaration and definitions
#include "starboard/decode_target.h"
void SbDecodeTargetRelease(SbDecodeTarget /*decode_target*/) {}
Parameters
Description
Helper function that is possibly useful to Starboard implementations that will release a decode target on the thread with the GLES context current.
Declaration
static SB_C_INLINE void SbDecodeTargetReleaseInGlesContext(
SbDecodeTargetGraphicsContextProvider* provider,
SbDecodeTarget decode_target) {
SbDecodeTargetRunInGlesContext(provider, &PrivateDecodeTargetReleaser,
(void*)decode_target);
}
Parameters
Description
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.
Declaration
static SB_C_INLINE void SbDecodeTargetRunInGlesContext(
SbDecodeTargetGraphicsContextProvider* provider,
SbDecodeTargetGlesContextRunnerTarget target,
void* target_context) {
provider->gles_context_runner(provider, target, target_context);
}
Parameters