diff options
author | Nicolas George <george@nsup.org> | 2016-10-23 14:57:41 +0300 |
---|---|---|
committer | Nicolas George <george@nsup.org> | 2016-11-03 23:23:55 +0300 |
commit | 0bd1be65e88d6a4f367e698d7a2b105424eb1905 (patch) | |
tree | 69cb89e9bfccaa3d67787261f351e78f9b994ebf /libavdevice/xcbgrab.c | |
parent | 4abe1ff08f1fb2a909c4a99bd9e44a81e2c3cc3d (diff) |
lavd/xcbgrab: do not try to create refcounted packets.
The framework will allocate a buffer and copy the data to it,
that takes time. But it avoids constently creating and
destroyng the shared memory segment, and that saves more time.
On my setup,
from ~200 to ~300 FPS at full screen (1920×1200),
from ~1400 to ~3300 at smaller size (640×480),
similar to legacy x11grab and confirmed by others.
Plus, shared memory segments are a scarce resource,
allocating potentially many is a bad idea.
Note: if the application were to drop all references to the
buffer before the next call to av_read_frame(), then passing
the shared memory segment as a refcounted buffer would be
even more efficient, but it is hard to guarantee, and it does
not happen with the ffmpeg command-line tool. Using a small
number of preallocated buffers and resorting to a copy when
the pool is exhausted would be a solution to get the better
of both worlds.
Diffstat (limited to 'libavdevice/xcbgrab.c')
-rw-r--r-- | libavdevice/xcbgrab.c | 65 |
1 files changed, 35 insertions, 30 deletions
diff --git a/libavdevice/xcbgrab.c b/libavdevice/xcbgrab.c index 9da46c8e0d..702e66c71f 100644 --- a/libavdevice/xcbgrab.c +++ b/libavdevice/xcbgrab.c @@ -49,6 +49,8 @@ typedef struct XCBGrabContext { const AVClass *class; + uint8_t *buffer; + xcb_connection_t *conn; xcb_screen_t *screen; xcb_window_t window; @@ -219,22 +221,16 @@ static int check_shm(xcb_connection_t *conn) return 0; } -static void dealloc_shm(void *unused, uint8_t *data) -{ - shmdt(data); -} - -static int xcbgrab_frame_shm(AVFormatContext *s, AVPacket *pkt) +static int allocate_shm(AVFormatContext *s) { 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; - uint8_t *data; int size = c->frame_size + AV_INPUT_BUFFER_PADDING_SIZE; - int id = shmget(IPC_PRIVATE, size, IPC_CREAT | 0777); - xcb_generic_error_t *e = NULL; + uint8_t *data; + int id; + if (c->buffer) + return 0; + id = shmget(IPC_PRIVATE, size, IPC_CREAT | 0777); if (id == -1) { char errbuf[1024]; int err = AVERROR(errno); @@ -243,15 +239,31 @@ static int xcbgrab_frame_shm(AVFormatContext *s, AVPacket *pkt) size, errbuf); return err; } - xcb_shm_attach(c->conn, c->segment, id, 0); + data = shmat(id, NULL, 0); + shmctl(id, IPC_RMID, 0); + if ((intptr_t)data == -1 || !data) + return AVERROR(errno); + c->buffer = data; + return 0; +} + +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_generic_error_t *e = NULL; + int ret; + + ret = allocate_shm(s); + if (ret < 0) + return ret; iq = xcb_shm_get_image(c->conn, drawable, c->x, c->y, c->width, c->height, ~0, XCB_IMAGE_FORMAT_Z_PIXMAP, c->segment, 0); - - xcb_shm_detach(c->conn, c->segment); - img = xcb_shm_get_image_reply(c->conn, iq, &e); xcb_flush(c->conn); @@ -264,25 +276,12 @@ static int xcbgrab_frame_shm(AVFormatContext *s, AVPacket *pkt) e->response_type, e->error_code, e->sequence, e->resource_id, e->minor_code, e->major_code); - shmctl(id, IPC_RMID, 0); return AVERROR(EACCES); } free(img); - data = shmat(id, NULL, 0); - shmctl(id, IPC_RMID, 0); - - if ((intptr_t)data == -1) - return AVERROR(errno); - - pkt->buf = av_buffer_create(data, size, dealloc_shm, NULL, 0); - if (!pkt->buf) { - shmdt(data); - return AVERROR(ENOMEM); - } - - pkt->data = pkt->buf->data; + pkt->data = c->buffer; pkt->size = c->frame_size; return 0; @@ -436,6 +435,12 @@ static av_cold int xcbgrab_read_close(AVFormatContext *s) { XCBGrabContext *ctx = s->priv_data; +#if CONFIG_LIBXCB_SHM + if (ctx->buffer) { + shmdt(ctx->buffer); + } +#endif + xcb_disconnect(ctx->conn); return 0; |