h264_metadata: Add option to delete filler data
[libav.git] / libavdevice / xcbgrab.c
1 /*
2 * XCB input grabber
3 * Copyright (C) 2014 Luca Barbato <lu_zero@gentoo.org>
4 *
5 * This file is part of Libav.
6 *
7 * Libav is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * Libav is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with Libav; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22 #include "config.h"
23
24 #include <stdlib.h>
25 #include <xcb/xcb.h>
26 #include <xcb/shape.h>
27
28 #if CONFIG_LIBXCB_XFIXES
29 #include <xcb/xfixes.h>
30 #endif
31
32 #if CONFIG_LIBXCB_SHM
33 #include <sys/shm.h>
34 #include <xcb/shm.h>
35 #endif
36
37 #include "libavutil/internal.h"
38 #include "libavutil/mathematics.h"
39 #include "libavutil/opt.h"
40 #include "libavutil/parseutils.h"
41 #include "libavutil/time.h"
42
43 #include "libavformat/avformat.h"
44 #include "libavformat/internal.h"
45
46 typedef struct XCBGrabContext {
47 const AVClass *class;
48
49 xcb_connection_t *conn;
50 xcb_screen_t *screen;
51 xcb_window_t window;
52 #if CONFIG_LIBXCB_SHM
53 xcb_shm_seg_t segment;
54 #endif
55 int64_t time_frame;
56 AVRational time_base;
57
58 int x, y;
59 int width, height;
60 int frame_size;
61 int bpp;
62
63 int draw_mouse;
64 int follow_mouse;
65 int show_region;
66 int region_border;
67 int centered;
68
69 const char *video_size;
70 const char *framerate;
71
72 int has_shm;
73 } XCBGrabContext;
74
75 #define FOLLOW_CENTER -1
76
77 #define OFFSET(x) offsetof(XCBGrabContext, x)
78 #define D AV_OPT_FLAG_DECODING_PARAM
79 static const AVOption options[] = {
80 { "x", "Initial x coordinate.", OFFSET(x), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, D },
81 { "y", "Initial y coordinate.", OFFSET(y), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, D },
82 { "grab_x", "Initial x coordinate.", OFFSET(x), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, D },
83 { "grab_y", "Initial y coordinate.", OFFSET(y), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, D },
84 { "video_size", "A string describing frame size, such as 640x480 or hd720.", OFFSET(video_size), AV_OPT_TYPE_STRING, {.str = "vga" }, 0, 0, D },
85 { "framerate", "", OFFSET(framerate), AV_OPT_TYPE_STRING, {.str = "ntsc" }, 0, 0, D },
86 { "draw_mouse", "Draw the mouse pointer.", OFFSET(draw_mouse), AV_OPT_TYPE_INT, { .i64 = 1 }, 0, 1, D },
87 { "follow_mouse", "Move the grabbing region when the mouse pointer reaches within specified amount of pixels to the edge of region.",
88 OFFSET(follow_mouse), AV_OPT_TYPE_INT, { .i64 = 0 }, FOLLOW_CENTER, INT_MAX, D, "follow_mouse" },
89 { "centered", "Keep the mouse pointer at the center of grabbing region when following.", 0, AV_OPT_TYPE_CONST, { .i64 = -1 }, INT_MIN, INT_MAX, D, "follow_mouse" },
90 { "show_region", "Show the grabbing region.", OFFSET(show_region), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, D },
91 { "region_border", "Set the region border thickness.", OFFSET(region_border), AV_OPT_TYPE_INT, { .i64 = 3 }, 1, 128, D },
92 { NULL },
93 };
94
95 static const AVClass xcbgrab_class = {
96 .class_name = "xcbgrab indev",
97 .item_name = av_default_item_name,
98 .option = options,
99 .version = LIBAVUTIL_VERSION_INT,
100 };
101
102 static int xcbgrab_reposition(AVFormatContext *s,
103 xcb_query_pointer_reply_t *p,
104 xcb_get_geometry_reply_t *geo)
105 {
106 XCBGrabContext *c = s->priv_data;
107 int x = c->x, y = c->y;
108 int w = c->width, h = c->height, f = c->follow_mouse;
109 int p_x, p_y;
110
111 if (!p || !geo)
112 return AVERROR(EIO);
113
114 p_x = p->win_x;
115 p_y = p->win_y;
116
117 if (f == FOLLOW_CENTER) {
118 x = p_x - w / 2;
119 y = p_y - h / 2;
120 } else {
121 int left = x + f;
122 int right = x + w - f;
123 int top = y + f;
124 int bottom = y + h + f;
125 if (p_x > right) {
126 x += p_x - right;
127 } else if (p_x < left) {
128 x -= left - p_x;
129 }
130 if (p_y > bottom) {
131 y += p_y - bottom;
132 } else if (p_y < top) {
133 y -= top - p_y;
134 }
135 }
136
137 c->x = FFMIN(FFMAX(0, x), geo->width - w);
138 c->y = FFMIN(FFMAX(0, y), geo->height - h);
139
140 return 0;
141 }
142
143 static int xcbgrab_frame(AVFormatContext *s, AVPacket *pkt)
144 {
145 XCBGrabContext *c = s->priv_data;
146 xcb_get_image_cookie_t iq;
147 xcb_get_image_reply_t *img;
148 xcb_drawable_t drawable = c->screen->root;
149 xcb_generic_error_t *e = NULL;
150 uint8_t *data;
151 int length, ret;
152
153 iq = xcb_get_image(c->conn, XCB_IMAGE_FORMAT_Z_PIXMAP, drawable,
154 c->x, c->y, c->width, c->height, ~0);
155
156 img = xcb_get_image_reply(c->conn, iq, &e);
157
158 if (e) {
159 av_log(s, AV_LOG_ERROR,
160 "Cannot get the image data "
161 "event_error: response_type:%u error_code:%u "
162 "sequence:%u resource_id:%u minor_code:%u major_code:%u.\n",
163 e->response_type, e->error_code,
164 e->sequence, e->resource_id, e->minor_code, e->major_code);
165 return AVERROR(EACCES);
166 }
167
168 if (!img)
169 return AVERROR(EAGAIN);
170
171 data = xcb_get_image_data(img);
172 length = xcb_get_image_data_length(img);
173
174 ret = av_new_packet(pkt, length);
175
176 if (!ret)
177 memcpy(pkt->data, data, length);
178
179 free(img);
180
181 return ret;
182 }
183
184 static void wait_frame(AVFormatContext *s, AVPacket *pkt)
185 {
186 XCBGrabContext *c = s->priv_data;
187 int64_t curtime, delay;
188 int64_t frame_time = av_rescale_q(1, c->time_base, AV_TIME_BASE_Q);
189
190 c->time_frame += frame_time;
191
192 for (;;) {
193 curtime = av_gettime();
194 delay = c->time_frame - curtime;
195 if (delay <= 0)
196 break;
197 av_usleep(delay);
198 }
199
200 pkt->pts = curtime;
201 }
202
203 #if CONFIG_LIBXCB_SHM
204 static int check_shm(xcb_connection_t *conn)
205 {
206 xcb_shm_query_version_cookie_t cookie = xcb_shm_query_version(conn);
207 xcb_shm_query_version_reply_t *reply;
208
209 reply = xcb_shm_query_version_reply(conn, cookie, NULL);
210 if (reply) {
211 free(reply);
212 return 1;
213 }
214
215 return 0;
216 }
217
218 static void dealloc_shm(void *unused, uint8_t *data)
219 {
220 shmdt(data);
221 }
222
223 static int xcbgrab_frame_shm(AVFormatContext *s, AVPacket *pkt)
224 {
225 XCBGrabContext *c = s->priv_data;
226 xcb_shm_get_image_cookie_t iq;
227 xcb_shm_get_image_reply_t *img;
228 xcb_drawable_t drawable = c->screen->root;
229 uint8_t *data;
230 int size = c->frame_size + AV_INPUT_BUFFER_PADDING_SIZE;
231 int id = shmget(IPC_PRIVATE, size, IPC_CREAT | 0777);
232 xcb_generic_error_t *e = NULL;
233
234 if (id == -1) {
235 char errbuf[1024];
236 int err = AVERROR(errno);
237 av_strerror(err, errbuf, sizeof(errbuf));
238 av_log(s, AV_LOG_ERROR, "Cannot get %d bytes of shared memory: %s.\n",
239 size, errbuf);
240 return err;
241 }
242
243 xcb_shm_attach(c->conn, c->segment, id, 0);
244
245 iq = xcb_shm_get_image(c->conn, drawable,
246 c->x, c->y, c->width, c->height, ~0,
247 XCB_IMAGE_FORMAT_Z_PIXMAP, c->segment, 0);
248
249 xcb_shm_detach(c->conn, c->segment);
250
251 img = xcb_shm_get_image_reply(c->conn, iq, &e);
252
253 xcb_flush(c->conn);
254
255 if (e) {
256 av_log(s, AV_LOG_ERROR,
257 "Cannot get the image data "
258 "event_error: response_type:%u error_code:%u "
259 "sequence:%u resource_id:%u minor_code:%u major_code:%u.\n",
260 e->response_type, e->error_code,
261 e->sequence, e->resource_id, e->minor_code, e->major_code);
262
263 shmctl(id, IPC_RMID, 0);
264 return AVERROR(EACCES);
265 }
266
267 free(img);
268
269 data = shmat(id, NULL, 0);
270 shmctl(id, IPC_RMID, 0);
271
272 if ((intptr_t)data == -1)
273 return AVERROR(errno);
274
275 pkt->buf = av_buffer_create(data, size, dealloc_shm, NULL, 0);
276 if (!pkt->buf) {
277 shmdt(data);
278 return AVERROR(ENOMEM);
279 }
280
281 pkt->data = pkt->buf->data;
282 pkt->size = c->frame_size;
283
284 return 0;
285 }
286 #endif /* CONFIG_LIBXCB_SHM */
287
288 #if CONFIG_LIBXCB_XFIXES
289 static int check_xfixes(xcb_connection_t *conn)
290 {
291 xcb_xfixes_query_version_cookie_t cookie;
292 xcb_xfixes_query_version_reply_t *reply;
293
294 cookie = xcb_xfixes_query_version(conn, XCB_XFIXES_MAJOR_VERSION,
295 XCB_XFIXES_MINOR_VERSION);
296 reply = xcb_xfixes_query_version_reply(conn, cookie, NULL);
297
298 if (reply) {
299 free(reply);
300 return 1;
301 }
302 return 0;
303 }
304
305 #define BLEND(target, source, alpha) \
306 (target) + ((source) * (255 - (alpha)) + 255 / 2) / 255
307
308 static void xcbgrab_draw_mouse(AVFormatContext *s, AVPacket *pkt,
309 xcb_query_pointer_reply_t *p,
310 xcb_get_geometry_reply_t *geo)
311 {
312 XCBGrabContext *gr = s->priv_data;
313 uint32_t *cursor;
314 uint8_t *image = pkt->data;
315 int stride = gr->bpp / 8;
316 xcb_xfixes_get_cursor_image_cookie_t cc;
317 xcb_xfixes_get_cursor_image_reply_t *ci;
318 int cx, cy, x, y, w, h, c_off, i_off;
319
320 cc = xcb_xfixes_get_cursor_image(gr->conn);
321 ci = xcb_xfixes_get_cursor_image_reply(gr->conn, cc, NULL);
322 if (!ci)
323 return;
324
325 cursor = xcb_xfixes_get_cursor_image_cursor_image(ci);
326 if (!cursor)
327 return;
328
329 cx = ci->x - ci->xhot;
330 cy = ci->y - ci->yhot;
331
332 x = FFMAX(cx, gr->x);
333 y = FFMAX(cy, gr->y);
334
335 w = FFMIN(cx + ci->width, gr->x + gr->width) - x;
336 h = FFMIN(cy + ci->height, gr->y + gr->height) - y;
337
338 c_off = x - cx;
339 i_off = x - gr->x;
340
341 cursor += (y - cy) * ci->width;
342 image += (y - gr->y) * gr->width * stride;
343
344 for (y = 0; y < h; y++) {
345 cursor += c_off;
346 image += i_off * stride;
347 for (x = 0; x < w; x++, cursor++, image += stride) {
348 int r, g, b, a;
349
350 r = *cursor & 0xff;
351 g = (*cursor >> 8) & 0xff;
352 b = (*cursor >> 16) & 0xff;
353 a = (*cursor >> 24) & 0xff;
354
355 if (!a)
356 continue;
357
358 if (a == 255) {
359 image[0] = r;
360 image[1] = g;
361 image[2] = b;
362 } else {
363 image[0] = BLEND(r, image[0], a);
364 image[1] = BLEND(g, image[1], a);
365 image[2] = BLEND(b, image[2], a);
366 }
367
368 }
369 cursor += ci->width - w - c_off;
370 image += (gr->width - w - i_off) * stride;
371 }
372
373 free(ci);
374 }
375 #endif /* CONFIG_LIBXCB_XFIXES */
376
377 static void xcbgrab_update_region(AVFormatContext *s)
378 {
379 XCBGrabContext *c = s->priv_data;
380 const uint32_t args[] = { c->x - c->region_border,
381 c->y - c->region_border };
382
383 xcb_configure_window(c->conn,
384 c->window,
385 XCB_CONFIG_WINDOW_X | XCB_CONFIG_WINDOW_Y,
386 args);
387 }
388
389 static int xcbgrab_read_packet(AVFormatContext *s, AVPacket *pkt)
390 {
391 XCBGrabContext *c = s->priv_data;
392 xcb_query_pointer_cookie_t pc;
393 xcb_get_geometry_cookie_t gc;
394 xcb_query_pointer_reply_t *p = NULL;
395 xcb_get_geometry_reply_t *geo = NULL;
396 int ret = 0;
397
398 wait_frame(s, pkt);
399
400 if (c->follow_mouse || c->draw_mouse) {
401 pc = xcb_query_pointer(c->conn, c->screen->root);
402 gc = xcb_get_geometry(c->conn, c->screen->root);
403 p = xcb_query_pointer_reply(c->conn, pc, NULL);
404 geo = xcb_get_geometry_reply(c->conn, gc, NULL);
405 }
406
407 if (c->follow_mouse && p->same_screen)
408 xcbgrab_reposition(s, p, geo);
409
410 if (c->show_region)
411 xcbgrab_update_region(s);
412
413 #if CONFIG_LIBXCB_SHM
414 if (c->has_shm && xcbgrab_frame_shm(s, pkt) < 0)
415 c->has_shm = 0;
416 #endif
417 if (!c->has_shm)
418 ret = xcbgrab_frame(s, pkt);
419
420 #if CONFIG_LIBXCB_XFIXES
421 if (ret >= 0 && c->draw_mouse && p->same_screen)
422 xcbgrab_draw_mouse(s, pkt, p, geo);
423 #endif
424
425 free(p);
426 free(geo);
427
428 return ret;
429 }
430
431 static av_cold int xcbgrab_read_close(AVFormatContext *s)
432 {
433 XCBGrabContext *ctx = s->priv_data;
434
435 xcb_disconnect(ctx->conn);
436
437 return 0;
438 }
439
440 static xcb_screen_t *get_screen(const xcb_setup_t *setup, int screen_num)
441 {
442 xcb_screen_iterator_t it = xcb_setup_roots_iterator(setup);
443 xcb_screen_t *screen = NULL;
444
445 for (; it.rem > 0; xcb_screen_next (&it)) {
446 if (!screen_num) {
447 screen = it.data;
448 break;
449 }
450
451 screen_num--;
452 }
453
454 return screen;
455 }
456
457 static int pixfmt_from_pixmap_format(AVFormatContext *s, int depth,
458 int *pix_fmt)
459 {
460 XCBGrabContext *c = s->priv_data;
461 const xcb_setup_t *setup = xcb_get_setup(c->conn);
462 const xcb_format_t *fmt = xcb_setup_pixmap_formats(setup);
463 int length = xcb_setup_pixmap_formats_length(setup);
464
465 *pix_fmt = 0;
466
467 while (length--) {
468 if (fmt->depth == depth) {
469 switch (depth) {
470 case 32:
471 if (fmt->bits_per_pixel == 32)
472 *pix_fmt = AV_PIX_FMT_ARGB;
473 break;
474 case 24:
475 if (fmt->bits_per_pixel == 32)
476 *pix_fmt = AV_PIX_FMT_RGB32;
477 else if (fmt->bits_per_pixel == 24)
478 *pix_fmt = AV_PIX_FMT_RGB24;
479 break;
480 case 16:
481 if (fmt->bits_per_pixel == 16)
482 *pix_fmt = AV_PIX_FMT_RGB565;
483 break;
484 case 15:
485 if (fmt->bits_per_pixel == 16)
486 *pix_fmt = AV_PIX_FMT_RGB555;
487 break;
488 case 8:
489 if (fmt->bits_per_pixel == 8)
490 *pix_fmt = AV_PIX_FMT_RGB8;
491 break;
492 }
493 }
494
495 if (*pix_fmt) {
496 c->bpp = fmt->bits_per_pixel;
497 c->frame_size = c->width * c->height * fmt->bits_per_pixel / 8;
498 return 0;
499 }
500
501 fmt++;
502 }
503 avpriv_report_missing_feature(s, "Mapping this pixmap format");
504
505 return AVERROR_PATCHWELCOME;
506 }
507
508 static int create_stream(AVFormatContext *s)
509 {
510 XCBGrabContext *c = s->priv_data;
511 AVStream *st = avformat_new_stream(s, NULL);
512 xcb_get_geometry_cookie_t gc;
513 xcb_get_geometry_reply_t *geo;
514 int ret;
515
516 if (!st)
517 return AVERROR(ENOMEM);
518
519 ret = av_parse_video_size(&c->width, &c->height, c->video_size);
520 if (ret < 0)
521 return ret;
522
523 ret = av_parse_video_rate(&st->avg_frame_rate, c->framerate);
524 if (ret < 0)
525 return ret;
526
527 avpriv_set_pts_info(st, 64, 1, 1000000);
528
529 gc = xcb_get_geometry(c->conn, c->screen->root);
530 geo = xcb_get_geometry_reply(c->conn, gc, NULL);
531
532 if (c->x + c->width > geo->width ||
533 c->y + c->height > geo->height) {
534 av_log(s, AV_LOG_ERROR,
535 "Capture area %dx%d at position %d.%d "
536 "outside the screen size %dx%d\n",
537 c->width, c->height,
538 c->x, c->y,
539 geo->width, geo->height);
540 return AVERROR(EINVAL);
541 }
542
543 c->time_base = (AVRational){ st->avg_frame_rate.den,
544 st->avg_frame_rate.num };
545 c->time_frame = av_gettime();
546
547 st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
548 st->codecpar->codec_id = AV_CODEC_ID_RAWVIDEO;
549 st->codecpar->width = c->width;
550 st->codecpar->height = c->height;
551
552 ret = pixfmt_from_pixmap_format(s, geo->depth, &st->codecpar->format);
553
554 free(geo);
555
556 return ret;
557 }
558
559 static void draw_rectangle(AVFormatContext *s)
560 {
561 XCBGrabContext *c = s->priv_data;
562 xcb_gcontext_t gc = xcb_generate_id(c->conn);
563 uint32_t mask = XCB_GC_FOREGROUND |
564 XCB_GC_BACKGROUND |
565 XCB_GC_LINE_WIDTH |
566 XCB_GC_LINE_STYLE |
567 XCB_GC_FILL_STYLE;
568 uint32_t values[] = { c->screen->black_pixel,
569 c->screen->white_pixel,
570 c->region_border,
571 XCB_LINE_STYLE_DOUBLE_DASH,
572 XCB_FILL_STYLE_SOLID };
573 xcb_rectangle_t r = { 1, 1,
574 c->width + c->region_border * 2 - 3,
575 c->height + c->region_border * 2 - 3 };
576
577 xcb_create_gc(c->conn, gc, c->window, mask, values);
578
579 xcb_poly_rectangle(c->conn, c->window, gc, 1, &r);
580 }
581
582 static void setup_window(AVFormatContext *s)
583 {
584 XCBGrabContext *c = s->priv_data;
585 uint32_t mask = XCB_CW_OVERRIDE_REDIRECT | XCB_CW_EVENT_MASK;
586 uint32_t values[] = { 1,
587 XCB_EVENT_MASK_EXPOSURE |
588 XCB_EVENT_MASK_STRUCTURE_NOTIFY };
589 xcb_rectangle_t rect = { 0, 0, c->width, c->height };
590
591 c->window = xcb_generate_id(c->conn);
592
593 xcb_create_window(c->conn, XCB_COPY_FROM_PARENT,
594 c->window,
595 c->screen->root,
596 c->x - c->region_border,
597 c->y - c->region_border,
598 c->width + c->region_border * 2,
599 c->height + c->region_border * 2,
600 0,
601 XCB_WINDOW_CLASS_INPUT_OUTPUT,
602 XCB_COPY_FROM_PARENT,
603 mask, values);
604
605 xcb_shape_rectangles(c->conn, XCB_SHAPE_SO_SUBTRACT,
606 XCB_SHAPE_SK_BOUNDING, XCB_CLIP_ORDERING_UNSORTED,
607 c->window,
608 c->region_border, c->region_border,
609 1, &rect);
610
611 xcb_map_window(c->conn, c->window);
612
613 draw_rectangle(s);
614 }
615
616 static av_cold int xcbgrab_read_header(AVFormatContext *s)
617 {
618 XCBGrabContext *c = s->priv_data;
619 int screen_num, ret;
620 const xcb_setup_t *setup;
621 char *host = s->filename[0] ? s->filename : NULL;
622 const char *opts = strchr(s->filename, '+');
623
624 if (opts) {
625 sscanf(opts, "%d,%d", &c->x, &c->y);
626 host = av_strdup(s->filename);
627 if (!host)
628 return AVERROR(ENOMEM);
629 host[opts - s->filename] = '\0';
630 }
631
632 c->conn = xcb_connect(host, &screen_num);
633
634 if ((ret = xcb_connection_has_error(c->conn))) {
635 av_log(s, AV_LOG_ERROR, "Cannot open display %s, error %d.\n",
636 s->filename[0] ? host : "default", ret);
637 if (opts)
638 av_freep(&host);
639 return AVERROR(EIO);
640 }
641
642 if (opts)
643 av_freep(&host);
644
645 setup = xcb_get_setup(c->conn);
646
647 c->screen = get_screen(setup, screen_num);
648 if (!c->screen) {
649 av_log(s, AV_LOG_ERROR, "The screen %d does not exist.\n",
650 screen_num);
651 xcbgrab_read_close(s);
652 return AVERROR(EIO);
653 }
654
655 ret = create_stream(s);
656
657 if (ret < 0) {
658 xcbgrab_read_close(s);
659 return ret;
660 }
661
662 #if CONFIG_LIBXCB_SHM
663 if ((c->has_shm = check_shm(c->conn)))
664 c->segment = xcb_generate_id(c->conn);
665 #endif
666
667 #if CONFIG_LIBXCB_XFIXES
668 if (c->draw_mouse) {
669 if (!(c->draw_mouse = check_xfixes(c->conn))) {
670 av_log(s, AV_LOG_WARNING,
671 "XFixes not available, cannot draw the mouse.\n");
672 }
673 if (c->bpp < 24) {
674 avpriv_report_missing_feature(s, "%d bits per pixel screen",
675 c->bpp);
676 c->draw_mouse = 0;
677 }
678 }
679 #endif
680
681 if (c->show_region)
682 setup_window(s);
683
684 return 0;
685 }
686
687 AVInputFormat ff_xcbgrab_demuxer = {
688 .name = "x11grab",
689 .long_name = NULL_IF_CONFIG_SMALL("X11 screen capture, using XCB"),
690 .priv_data_size = sizeof(XCBGrabContext),
691 .read_header = xcbgrab_read_header,
692 .read_packet = xcbgrab_read_packet,
693 .read_close = xcbgrab_read_close,
694 .flags = AVFMT_NOFILE,
695 .priv_class = &xcbgrab_class,
696 };