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draft of new OSD engine:
========================
written by A'rpi
including ideas from mailing list from Jiri Svoboda, Tobias Diedrich,
Artur Zaprzala, Michael Niedermayer, Felix Buenemann, LGB
requirements:
- be able to do partial rendering, within a given bounding box
useful when parts of the OSD are outside of the image and has to be
updated only when OSD changes, or even has different colorspace
- text should be rendered in 2-pass way: 1. alpha 2. pixels
so char's alpha won't overwrite previous char, and may be faster
- OSD elements should be cached - so rendering once into the cache and
reuse this while it's unchanged
- color support (colorspace could be YA, YUVA, RGB)
- change brightness, saturation, hue of chars ???
- way to disable alphablending, and use black outline (FAST_OSD now)
- respect movie and monitor aspect, so OSD is rendered/scaled correctly
eg. for SVCD/anamorphic DVD with hardware scaling (now OSD is squashed)
- develop some text-based apps: osdterm, osdzilla etc ;)
Ok. The basic idea of my design is using 'OSD objects', a data structure
in a 1 (or 2?) way linked list.
There would be different object types, sharing type-dependent data in a
union. The basic types: box, text, symbol, progressbar, group.
Group would be a special type, grouping other OSD objects together,
with a common x,y and boundingbox. Useful for grouping symbol+progrbar
or multiline subtitle text.
Each object could have flags, for example:
- visible (set if we should display it)
- color (set if it's YUVA not YA)
- cached (set when there is a cached rendered variant)
- bbox updated (should be set when recalc bbox, reset when change params)
- several flags to control positioning. for example, x;y could be
absolute coordinates, or percent. flags to set left/center/right alignment...
- start and end timestamp, to automagically set/reset visible flag
OK, my first draft:
typedef struct mp_osd_obj_s {
struct mp_osd_obj_s* next;
unsigned char type;
unsigned char alignment; // 2 bits: x;y percentages, 2 bits: x;y relative to parent; 2 bits: alignment left/right/center
unsigned short flags;
int x,y; // coords
unsigned char color[4]; // YUVA
mp_osd_bbox_t bbox; // bounding box
unsigned int start,duration; // PTS
union {
struct {
int x1,y1,x2,y2;
} line;
struct {
int x,y,w,h;
} rect;
struct {
char* text;
mp_font_t* font;
} text;
struct {
int symbol; // unicode
mp_font_t* font;
} symbol;
struct {
float value;
mp_font_t* font;
} pbar;
struct {
int w,h;
unsigned char* image;
unsigned int* palette;
} spu; // FIXME!
struct {
struct mp_osd_obj_s* children;
} group;
} params;
} mp_osd_obj_t;
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