1 #ifndef _MOVIT_YCBCR_422INTERLEAVED_INPUT_H
2 #define _MOVIT_YCBCR_422INTERLEAVED_INPUT_H 1
4 // YCbCr422InterleavedInput is for handling 4:2:2 interleaved 8-bit Y'CbCr,
5 // which you can get from e.g. certain capture cards. (Most other Y'CbCr
6 // encodings are planar, which is handled by YCbCrInput.) Currently we only
7 // handle the UYVY variant, although YUY2 should be easy to support if needed.
9 // Horizontal chroma placement is freely choosable as with YCbCrInput,
10 // but BT.601 (which at least DeckLink claims to conform to, under the
11 // name CCIR 601) seems to specify chroma positioning to the far left
12 // (that is 0.0); BT.601 Annex 1 (page 7) says “C R and C B samples co-sited
13 // with odd (1st, 3rd, 5th, etc.) Y samples in each line”, and I assume they do
14 // not start counting from 0 when they use the “1st” moniker.
16 // Interpolation is bilinear as in YCbCrInput (done by the GPU's normal
17 // scaling, except for the Y channel which of course needs some fiddling),
18 // and is done in non-linear light (since that's what everything specifies,
19 // except Rec. 2020 lets you choose between the two). A higher-quality
20 // choice would be to use a single pass of ResampleEffect to scale the
21 // chroma, but for now we are consistent between the two.
23 // There is a disparity between the interleaving and the way OpenGL typically
24 // expects to sample. In lieu of accessible hardware support (a lot of hardware
25 // supports native interleaved 4:2:2 sampling, but OpenGL drivers seem to
26 // rarely support it), we simply upload the same data twice; once as a
27 // full-width RG texture (from which we sample luma) and once as a half-width
28 // RGBA texture (from which we sample chroma). We throw away half of the color
29 // channels each time, so bandwidth is wasted, but it makes for a very
30 // uncomplicated shader.
36 #include "effect_chain.h"
37 #include "image_format.h"
45 class YCbCr422InterleavedInput : public Input {
47 // <ycbcr_format> must be consistent with 4:2:2 sampling; specifically:
49 // * chroma_subsampling_x must be 2.
50 // * chroma_subsampling_y must be 1.
52 // <width> must obviously be an even number. It is the true width of the image
53 // in pixels, ie., the number of horizontal luma samples.
54 YCbCr422InterleavedInput(const ImageFormat &image_format,
55 const YCbCrFormat &ycbcr_format,
56 unsigned width, unsigned height);
57 ~YCbCr422InterleavedInput();
59 virtual std::string effect_type_id() const { return "YCbCr422InterleavedInput"; }
61 virtual bool can_output_linear_gamma() const { return false; }
62 virtual AlphaHandling alpha_handling() const { return OUTPUT_BLANK_ALPHA; }
64 std::string output_fragment_shader();
66 // Uploads the texture if it has changed since last time.
67 void set_gl_state(GLuint glsl_program_num, const std::string& prefix, unsigned *sampler_num);
69 unsigned get_width() const { return width; }
70 unsigned get_height() const { return height; }
71 Colorspace get_color_space() const { return image_format.color_space; }
72 GammaCurve get_gamma_curve() const { return image_format.gamma_curve; }
73 virtual bool can_supply_mipmaps() const { return false; }
75 // Tells the input where to fetch the actual pixel data. Note that if you change
76 // this data, you must either call set_pixel_data() again (using the same pointer
77 // is fine), or invalidate_pixel_data(). Otherwise, the texture won't be re-uploaded
78 // on subsequent frames.
80 // The data can either be a regular pointer (if pbo==0), or a byte offset
81 // into a PBO. The latter will allow you to start uploading the texture data
82 // asynchronously to the GPU, if you have any CPU-intensive work between the
83 // call to set_pixel_data() and the actual rendering. Also, since we upload
84 // the data twice, using a PBO can save texture upload bandwidth. In either case,
85 // the pointer (and PBO, if set) has to be valid at the time of the render call.
86 void set_pixel_data(const unsigned char *pixel_data, GLuint pbo = 0)
88 this->pixel_data = pixel_data;
90 invalidate_pixel_data();
93 void invalidate_pixel_data();
95 void set_pitch(unsigned pitch) {
96 assert(pitch % ycbcr_format.chroma_subsampling_x == 0);
97 pitches[CHANNEL_LUMA] = pitch;
98 pitches[CHANNEL_CHROMA] = pitch / ycbcr_format.chroma_subsampling_x;
99 invalidate_pixel_data();
102 virtual void inform_added(EffectChain *chain)
104 resource_pool = chain->get_resource_pool();
107 bool set_int(const std::string& key, int value);
110 ImageFormat image_format;
111 YCbCrFormat ycbcr_format;
114 // Luma texture is 0, chroma texture is 1.
119 GLuint texture_num[2];
123 unsigned width, height;
124 const unsigned char *pixel_data;
125 ResourcePool *resource_pool;
130 #endif // !defined(_MOVIT_YCBCR_422INTERLEAVED_INPUT_H)