score::gfx::I420Encoder Struct Reference

GPU RGBA->I420 encoder (planar 4:2:0). More...

Inheritance diagram for score::gfx::I420Encoder:

Detailed Description

GPU RGBA->I420 encoder (planar 4:2:0).

Three render passes: Pass 1: Y plane -> R8 at full resolution Pass 2: U plane -> R8 at half resolution (width/2 × height/2) Pass 3: V plane -> R8 at half resolution (width/2 × height/2)

Three readbacks. The caller concatenates Y + U + V for GStreamer video/x-raw,format=I420.

FIXME: is there any way to do it in one pass? MRTs don't seem to work due to the size limitation (same size for everyone)

Classes
struct	PlaneResources

Public Member Functions
void	initPlane (QRhi &rhi, const RenderState &state, QRhiTexture *inputRGBA, PlaneResources &plane, int w, int h, const char *fragTemplate, const QString &colorConversion)
void	execPlane (QRhi &rhi, QRhiCommandBuffer &cb, PlaneResources &plane, int w, int h)
void	init (QRhi &rhi, const RenderState &state, QRhiTexture *inputRGBA, int width, int height, const QString &colorConversion=colorMatrixOut()) override
void	exec (QRhi &rhi, QRhiCommandBuffer &cb) override
int	planeCount () const override
	Number of readback planes (1 for UYVY, 2 for NV12, 3 for I420).
const QRhiReadbackResult &	readback (int plane) const override
	Get the readback result for a given plane. Valid after endOffscreenFrame.
void	release () override
	Release all GPU resources.

Public Attributes
PlaneResources	m_planes [3]
QRhiSampler *	m_sampler {}
int	m_width {}
int	m_height {}

Static Public Attributes
static constexpr const char *	y_frag
static constexpr const char *	u_frag
static constexpr const char *	v_frag
Static Public Attributes inherited from score::gfx::GPUVideoEncoder
static constexpr const char *	vertex_shader
static constexpr const char *	rgb_to_yuv_glsl
static constexpr const char *	y_flip_glsl
	Fragment shader Y-flip: on GL, flip v_texcoord.y. On Metal/HLSL, no flip.

Member Function Documentation

exec()

void score::gfx::I420Encoder::exec ( QRhi &  rhi, QRhiCommandBuffer &  cb  )

inlineoverridevirtual

Execute the conversion pass. Call inside beginOffscreenFrame/endOffscreenFrame. Renders the conversion shader and schedules GPU->CPU readback(s).

Implements score::gfx::GPUVideoEncoder.

init()

void score::gfx::I420Encoder::init ( QRhi &  rhi, const RenderState &  state, QRhiTexture *  inputRGBA, int  width, int  height, const QString &  colorConversion = colorMatrixOut()  )

inlineoverridevirtual

Create render targets, textures, samplers, and the graphics pipeline.

Parameters

rhi	The QRhi instance.
state	The render state (for shader compilation).
inputRGBA	The scene RGBA texture to read from.
width	Source width in pixels.
height	Source height in pixels.
colorConversion	GLSL code from colorMatrixOut() defining convert_from_rgb(). If empty, defaults to BT.709 full range.

Implements score::gfx::GPUVideoEncoder.

planeCount()

int score::gfx::I420Encoder::planeCount ( ) const

inlineoverridevirtual

Number of readback planes (1 for UYVY, 2 for NV12, 3 for I420).

Implements score::gfx::GPUVideoEncoder.

readback()

const QRhiReadbackResult & score::gfx::I420Encoder::readback ( int  plane ) const

inlineoverridevirtual

Get the readback result for a given plane. Valid after endOffscreenFrame.

Implements score::gfx::GPUVideoEncoder.

release()

void score::gfx::I420Encoder::release ( )

inlineoverridevirtual

Release all GPU resources.

Implements score::gfx::GPUVideoEncoder.

Member Data Documentation

u_frag

constexpr const char* score::gfx::I420Encoder::u_frag

staticconstexpr

Initial value:

= R"_(#version 450
    layout(location = 0) in vec2 v_texcoord;
    layout(location = 0) out vec4 fragColor;
    layout(binding = 3) uniform sampler2D src_tex;
    )_" "%1" R"_(
    vec2 flip_y(vec2 tc) {
      return tc;
      return vec2(tc.x, 1.0 - tc.y);
    }
    void main() {
      vec3 rgb = texture(src_tex, flip_y(v_texcoord)).rgb;
      vec3 yuv = convert_from_rgb(rgb);
      fragColor = vec4(yuv.y, 0.0, 0.0, 1.0);
    }
  )_"

v_frag

constexpr const char* score::gfx::I420Encoder::v_frag

staticconstexpr

Initial value:

= R"_(#version 450
    layout(location = 0) in vec2 v_texcoord;
    layout(location = 0) out vec4 fragColor;
    layout(binding = 3) uniform sampler2D src_tex;
    )_" "%1" R"_(
    vec2 flip_y(vec2 tc) {
      return tc;
      return vec2(tc.x, 1.0 - tc.y);
    }
    void main() {
      vec3 rgb = texture(src_tex, flip_y(v_texcoord)).rgb;
      vec3 yuv = convert_from_rgb(rgb);
      fragColor = vec4(yuv.z, 0.0, 0.0, 1.0);
    }
  )_"

y_frag

constexpr const char* score::gfx::I420Encoder::y_frag

staticconstexpr

Initial value:

= R"_(#version 450
    layout(location = 0) in vec2 v_texcoord;
    layout(location = 0) out vec4 fragColor;
    layout(binding = 3) uniform sampler2D src_tex;
    )_" "%1" R"_(
    vec2 flip_y(vec2 tc) {
      return tc;
      return vec2(tc.x, 1.0 - tc.y);
    }
    void main() {
      vec3 rgb = texture(src_tex, flip_y(v_texcoord)).rgb;
      vec3 yuv = convert_from_rgb(rgb);
      fragColor = vec4(yuv.x, 0.0, 0.0, 1.0);
    }
  )_"

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The documentation for this struct was generated from the following file:

• I420.hpp