[jitter] Realtime video buffer with variable speed access

Hello,

A question about time. Could it be possible to record live video with  
a jit.qt.grab, and store it in real time in a variable access buffer,  
which would be read at variable speed rates ?

For example we would read this buffer at the same speed than the  
incoming live video (= no delay), then we would read it slower, at  
different speeds (=> creating an increasing delay compared with the  
realtime), and then for example accelerate again the lecture speed of  
the buffer, in order to re-synchronise it with the incoming realtime  
video.

I tried to make it with the "video delay" example published by  
Jonathan Lee Marcus on the list (thanks again), using matrix  
dimensions to store frames read with the srcdimstart and srcdimend  
cmds, but I didn't get it : I can't read these stored matrix at  
different speed rates. Sorry if it's obvious, I'm not very  
comfortable with this method. I post the patch again for reference.

Thanks & best regards,

Thierry Fournier

max v2;
#N vpatcher 31 63 1038 714;
#P origin 66 321;
#P user jit.pwindow 362 345 322 242 0 1 0 0 1 0;
#P window setfont "Sans Serif" 9.;
#P number 377 237 35 9 0 0 0 3 0 0 0 221 221 221 222 222 222 0 0 0;
#P user jit.fpsgui 64 136 60 196617 0;
#P message 671 42 26 196617 500;
#P newex 671 21 45 196617 loadbang;
#P window setfont "Sans Serif" 12.;
#P window linecount 2;
#P comment 711 350 132 196620 simple video delay jonathan lee marcus;
#P toggle 28 38 15 0;
#P window setfont "Sans Serif" 9.;
#P window linecount 1;
#P newex 28 58 64 196617 qmetro 60;
#P message 139 58 38 196617 close;
#P message 96 36 124 196617 open \, framerate 60.;
#P newex 28 96 238 196617 jit.qt.grab 320 240 @vmode 1 @unique 1;
#P user jit.pwindow 27 348 322 242 0 1 0 0 1 0;
#P comment 744 221 136 196617 <--less___delay___more-->;
#P message 685 184 42 196617 size \$1;
#P newex 377 263 129 196617 expr (($i1+$i2)-$i3)%$i4;
#P newex 671 83 27 196617 + 1;
#P message 379 134 81 196617 dim 320 240 \$1;
#P message 671 129 74 196617 max \$1 \, min 0;
#P comment 705 63 132 196617 <-maximum frames of delay;
#P number 671 61 35 9 0 0 0 3 0 0 0 221 221 221 222 222 222 0 0 0;
#P number 671 150 35 9 0 500 3 3 0 0 0 221 221 221 222 222 222 0 0 0;
#P comment 707 151 136 196617 <-number of frames to delay;
#P newex 377 209 50 196617 r rtdelay;
#P newex 363 307 262 196617 jit.matrix dave 4 char 320 240 @usesrcdim  
1 @adapt 0;
#P message 377 286 205 196617 srcdimstart 0 0 \$1 \, srcdimend 319  
239 \$1;
#P user hslider 685 203 19 236 501 1 0 0;
#P newex 470 132 50 196617 s rtdelay;
#N counter 0 0 160;
#X flags 0 0;
#P newobj 380 87 82 196617 counter 0 0 160;
#P message 378 166 203 196617 dstdimstart 0 0 \$1 \, dstdimend 319  
239 \$1;
#P newex 363 188 283 196617 jit.matrix jack 4 char 320 240 161  
@usedstdim 1 @interp 0;
#P newex 363 47 27 196617 t l b;
#P connect 24 0 23 0;
#P fasten 22 0 20 0 144 94 33 94;
#P fasten 21 0 20 0 101 94 33 94;
#P fasten 23 0 20 0 33 94 33 94;
#P connect 20 0 19 0;
#P fasten 20 0 28 0 33 125 69 125;
#P fasten 20 0 0 0 33 125 311 125 311 35 368 35;
#P lcolor 13;
#P fasten 14 0 1 0 384 154 368 154;
#P fasten 2 0 1 0 383 185 368 185;
#P connect 0 0 1 0;
#P lcolor 13;
#P connect 1 0 7 0;
#P lcolor 13;
#P connect 6 0 7 0;
#P connect 7 0 30 0;
#P connect 8 0 29 0;
#P connect 29 0 16 0;
#P connect 16 0 6 0;
#P fasten 3 0 2 0 385 112 374 112 374 160 383 160;
#P fasten 15 0 14 0 676 120 384 120;
#P connect 0 1 3 0;
#P fasten 15 0 16 1 676 114 663 114 663 235 421 235;
#P fasten 11 0 3 4 676 76 457 76;
#P fasten 10 0 16 2 676 245 460 245;
#P fasten 3 0 4 0 385 118 475 118;
#P fasten 15 0 16 3 676 114 660 114 660 224 499 224;
#P connect 26 0 27 0;
#P connect 27 0 11 0;
#P connect 11 0 15 0;
#P fasten 11 0 13 0 676 79 703 79 703 125 676 125;
#P connect 13 0 10 0;
#P fasten 5 0 10 0 690 227 667 227 667 147 676 147;
#P fasten 15 0 17 0 676 106 850 106 850 179 690 179;
#P connect 17 0 5 0;
#P pop;