[FFmpeg-devel] [PATCH] x11grab: capture a window instead of the whole screen
sgerwk at aol.com
sgerwk at aol.com
Wed Feb 10 19:15:15 EET 2021
On Sat, 6 Feb 2021, Paul B Mahol wrote:
> What happens if you use non-existing window?
I added an error message for this case, but the output video is still created
(empty). Is there a value I can return to avoid this?
On Sun, 7 Feb 2021, Andriy Gelman wrote:
> Also the commit title should start with avdevice/xcbgrab: or lavd/xcbgrab:
>
done
>
> If you try with -show_region 1, the border gets drawn in the wrong place.
>
fixed
I also fixed the misalignement of draw_mouse I didn't notice last time.
>>
>> + at item window_id
>> +Grab this window, instead of the whole screen.
>> +
>
> I think it would be useful to say how to get a window id.
> Probably worth adding what happens if the window size changes or it
> disappears.
>
Done. Recording also ends when the window is iconified or reduced in size beyond
the video size.
For now I disabled follow_mouse and select_region when window_id is given.
> xcb_window_t is uint32_t, so max should be UINT32_MAX?
Indeed.
>> @@ -825,6 +827,9 @@ static av_cold int xcbgrab_read_header(AVFormatContext
>> *s)
>> return AVERROR(EIO);
>> }
>>
>> + if (c->window_id == 0)
>> + c->window_id = c->screen->root;
>> +
>
> Can 0 be a valid window_id? Maybe it's better to use -1 for default. I saw the
> function xcb_generate_id() returns -1 on error.
>
0 is not a valid x11 identifier, but it's better to use the XCB_NONE macro for
it (in Xlib and higher-level libraries, it's "None")
Thanks!
> Thanks,
> --
> Andriy
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-------------- next part --------------
From e13c1be7abd6989b3ad80fd8086fe6a0819fd810 Mon Sep 17 00:00:00 2001
From: sgerwk <sgerwk at aol.com>
Date: Wed, 10 Feb 2021 17:36:00 +0100
Subject: [PATCH] libavdevice/xcbgrab: option for grabbing a window instead of
desktop
---
doc/indevs.texi | 14 +++++++-
libavdevice/xcbgrab.c | 79 ++++++++++++++++++++++++++++++++-----------
2 files changed, 72 insertions(+), 21 deletions(-)
diff --git a/doc/indevs.texi b/doc/indevs.texi
index 3924d03..48fd2b1 100644
--- a/doc/indevs.texi
+++ b/doc/indevs.texi
@@ -1564,8 +1564,20 @@ With @var{follow_mouse}:
ffmpeg -f x11grab -follow_mouse centered -show_region 1 -framerate 25 -video_size cif -i :0.0 out.mpg
@end example
+ at item window_id
+Grab this window, instead of the whole screen.
+
+The id of a window can be found by xwininfo(1), possibly with options -tree and
+-root.
+
+If the window is later enlarged, the new area is not recorded. Video ends when
+the window is closed, unmapped (i.e., iconified) or shrunk beyond the video
+size (which defaults to the initial window size).
+
+This option disables options @option{follow_mouse} and @option{select_region}.
+
@item video_size
-Set the video frame size. Default is the full desktop.
+Set the video frame size. Default is the full desktop or window.
@item grab_x
@item grab_y
diff --git a/libavdevice/xcbgrab.c b/libavdevice/xcbgrab.c
index be5d5ea..7697090 100644
--- a/libavdevice/xcbgrab.c
+++ b/libavdevice/xcbgrab.c
@@ -60,6 +60,8 @@ typedef struct XCBGrabContext {
AVRational time_base;
int64_t frame_duration;
+ xcb_window_t window_id;
+ int win_x, win_y;
int x, y;
int width, height;
int frame_size;
@@ -82,6 +84,7 @@ typedef struct XCBGrabContext {
#define OFFSET(x) offsetof(XCBGrabContext, x)
#define D AV_OPT_FLAG_DECODING_PARAM
static const AVOption options[] = {
+ { "window_id", "Window to capture", OFFSET(window_id), AV_OPT_TYPE_INT, { .i64 = XCB_NONE }, 0, UINT32_MAX, D },
{ "x", "Initial x coordinate.", OFFSET(x), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, D },
{ "y", "Initial y coordinate.", OFFSET(y), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, D },
{ "grab_x", "Initial x coordinate.", OFFSET(x), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, D },
@@ -157,7 +160,7 @@ static int xcbgrab_frame(AVFormatContext *s, AVPacket *pkt)
XCBGrabContext *c = s->priv_data;
xcb_get_image_cookie_t iq;
xcb_get_image_reply_t *img;
- xcb_drawable_t drawable = c->screen->root;
+ xcb_drawable_t drawable = c->window_id;
xcb_generic_error_t *e = NULL;
uint8_t *data;
int length;
@@ -267,7 +270,7 @@ static int xcbgrab_frame_shm(AVFormatContext *s, AVPacket *pkt)
XCBGrabContext *c = s->priv_data;
xcb_shm_get_image_cookie_t iq;
xcb_shm_get_image_reply_t *img;
- xcb_drawable_t drawable = c->screen->root;
+ xcb_drawable_t drawable = c->window_id;
xcb_generic_error_t *e = NULL;
AVBufferRef *buf;
xcb_shm_seg_t segment;
@@ -355,17 +358,17 @@ static void xcbgrab_draw_mouse(AVFormatContext *s, AVPacket *pkt,
cx = ci->x - ci->xhot;
cy = ci->y - ci->yhot;
- x = FFMAX(cx, gr->x);
- y = FFMAX(cy, gr->y);
+ x = FFMAX(cx, gr->win_x + gr->x);
+ y = FFMAX(cy, gr->win_y + gr->y);
- w = FFMIN(cx + ci->width, gr->x + gr->width) - x;
- h = FFMIN(cy + ci->height, gr->y + gr->height) - y;
+ w = FFMIN(cx + ci->width, gr->win_x + gr->x + gr->width) - x;
+ h = FFMIN(cy + ci->height, gr->win_y + gr->y + gr->height) - y;
c_off = x - cx;
- i_off = x - gr->x;
+ i_off = x - gr->x - gr->win_x;
cursor += (y - cy) * ci->width;
- image += (y - gr->y) * gr->width * stride;
+ image += (y - gr->y - gr->win_y) * gr->width * stride;
for (y = 0; y < h; y++) {
cursor += c_off;
@@ -403,8 +406,8 @@ static void xcbgrab_draw_mouse(AVFormatContext *s, AVPacket *pkt,
static void xcbgrab_update_region(AVFormatContext *s)
{
XCBGrabContext *c = s->priv_data;
- const uint32_t args[] = { c->x - c->region_border,
- c->y - c->region_border };
+ const uint32_t args[] = { c->win_x + c->x - c->region_border,
+ c->win_y + c->y - c->region_border };
xcb_configure_window(c->conn,
c->window,
@@ -417,16 +420,22 @@ static int xcbgrab_read_packet(AVFormatContext *s, AVPacket *pkt)
XCBGrabContext *c = s->priv_data;
xcb_query_pointer_cookie_t pc;
xcb_get_geometry_cookie_t gc;
+ xcb_translate_coordinates_cookie_t tc;
xcb_query_pointer_reply_t *p = NULL;
xcb_get_geometry_reply_t *geo = NULL;
+ xcb_translate_coordinates_reply_t *translate = NULL;
int ret = 0;
int64_t pts;
pts = wait_frame(s, pkt);
- if (c->follow_mouse || c->draw_mouse) {
- pc = xcb_query_pointer(c->conn, c->screen->root);
- gc = xcb_get_geometry(c->conn, c->screen->root);
+ if (c->window_id == c->screen->root) {
+ c->win_x = 0;
+ c->win_y = 0;
+ }
+ if (c->follow_mouse || c->draw_mouse || c->window_id != c->screen->root) {
+ pc = xcb_query_pointer(c->conn, c->window_id);
+ gc = xcb_get_geometry(c->conn, c->window_id);
p = xcb_query_pointer_reply(c->conn, pc, NULL);
if (!p) {
av_log(s, AV_LOG_ERROR, "Failed to query xcb pointer\n");
@@ -438,6 +447,12 @@ static int xcbgrab_read_packet(AVFormatContext *s, AVPacket *pkt)
free(p);
return AVERROR_EXTERNAL;
}
+ tc = xcb_translate_coordinates(c->conn, c->window_id, c->screen->root, geo->x, geo->y);
+ translate = xcb_translate_coordinates_reply(c->conn, tc, NULL);
+ if (!translate)
+ return AVERROR_EXTERNAL;
+ c->win_x = translate->dst_x;
+ c->win_y = translate->dst_y;
}
if (c->follow_mouse && p->same_screen)
@@ -447,7 +462,7 @@ static int xcbgrab_read_packet(AVFormatContext *s, AVPacket *pkt)
xcbgrab_update_region(s);
#if CONFIG_LIBXCB_SHM
- if (c->has_shm && xcbgrab_frame_shm(s, pkt) < 0) {
+ if (c->has_shm && (ret = xcbgrab_frame_shm(s, pkt)) == AVERROR(ENOMEM)) {
av_log(s, AV_LOG_WARNING, "Continuing without shared memory.\n");
c->has_shm = 0;
}
@@ -558,7 +573,9 @@ static int create_stream(AVFormatContext *s)
XCBGrabContext *c = s->priv_data;
AVStream *st = avformat_new_stream(s, NULL);
xcb_get_geometry_cookie_t gc;
+ xcb_translate_coordinates_cookie_t tc;
xcb_get_geometry_reply_t *geo;
+ xcb_translate_coordinates_reply_t *translate;
int64_t frame_size_bits;
int ret;
@@ -571,11 +588,20 @@ static int create_stream(AVFormatContext *s)
avpriv_set_pts_info(st, 64, 1, 1000000);
- gc = xcb_get_geometry(c->conn, c->screen->root);
+ gc = xcb_get_geometry(c->conn, c->window_id);
geo = xcb_get_geometry_reply(c->conn, gc, NULL);
- if (!geo)
+ if (!geo) {
+ av_log(s, AV_LOG_ERROR, "Can't find window '0x%x', aborting.\n", c->window_id);
+ return AVERROR_EXTERNAL;
+ }
+
+ tc = xcb_translate_coordinates(c->conn, c->window_id, c->screen->root, geo->x, geo->y);
+ translate = xcb_translate_coordinates_reply(c->conn, tc, NULL);
+ if (!translate)
return AVERROR_EXTERNAL;
+ c->win_x = translate->dst_x;
+ c->win_y = translate->dst_y;
if (!c->width || !c->height) {
c->width = geo->width;
c->height = geo->height;
@@ -750,7 +776,7 @@ static int select_region(AVFormatContext *s)
press_position = (xcb_point_t){ press->event_x, press->event_y };
rectangle.x = press_position.x;
rectangle.y = press_position.y;
- xcb_poly_rectangle(conn, root_window, gc, 1, &rectangle);
+ xcb_poly_rectangle(conn, c->window_id, gc, 1, &rectangle);
was_pressed = 1;
break;
}
@@ -759,14 +785,14 @@ static int select_region(AVFormatContext *s)
xcb_motion_notify_event_t *motion =
(xcb_motion_notify_event_t *)event;
xcb_point_t cursor_position = { motion->event_x, motion->event_y };
- xcb_poly_rectangle(conn, root_window, gc, 1, &rectangle);
+ xcb_poly_rectangle(conn, c->window_id, gc, 1, &rectangle);
rectangle = rectangle_from_corners(&press_position, &cursor_position);
- xcb_poly_rectangle(conn, root_window, gc, 1, &rectangle);
+ xcb_poly_rectangle(conn, c->window_id, gc, 1, &rectangle);
}
break;
}
case XCB_BUTTON_RELEASE: {
- xcb_poly_rectangle(conn, root_window, gc, 1, &rectangle);
+ xcb_poly_rectangle(conn, c->window_id, gc, 1, &rectangle);
done = 1;
break;
}
@@ -830,6 +856,19 @@ static av_cold int xcbgrab_read_header(AVFormatContext *s)
return AVERROR(EIO);
}
+ if (c->window_id == XCB_NONE)
+ c->window_id = c->screen->root;
+ else {
+ if (c->select_region) {
+ av_log(s, AV_LOG_WARNING, "select_region ignored with window_id.\n");
+ c->select_region = 0;
+ }
+ if (c->follow_mouse) {
+ av_log(s, AV_LOG_WARNING, "follow_mouse ignored with window_id.\n");
+ c->follow_mouse = 0;
+ }
+ }
+
if (c->select_region) {
ret = select_region(s);
if (ret < 0) {
--
2.30.0
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