Also by wrapping the SHM buffer in an AVBufferRef we eliminate yet another
possible memcpy improving performance.
Signed-off-by: Marton Balint <c...@passwd.hu>
---
libavdevice/xcbgrab.c | 79 ++++++++++++++++++++++++++++++---------------------
1 file changed, 47 insertions(+), 32 deletions(-)
diff --git a/libavdevice/xcbgrab.c b/libavdevice/xcbgrab.c
index 158f381c04..82ea09ca96 100644
--- a/libavdevice/xcbgrab.c
+++ b/libavdevice/xcbgrab.c
@@ -49,13 +49,11 @@
typedef struct XCBGrabContext {
const AVClass *class;
- uint8_t *buffer;
-
xcb_connection_t *conn;
xcb_screen_t *screen;
xcb_window_t window;
#if CONFIG_LIBXCB_SHM
- xcb_shm_seg_t segment;
+ AVBufferPool *shm_pool;
#endif
int64_t time_frame;
AVRational time_base;
@@ -231,31 +229,35 @@ static int check_shm(xcb_connection_t *conn)
return 0;
}
-static int allocate_shm(AVFormatContext *s)
+static void free_shm_buffer(void *opaque, uint8_t *data)
{
- XCBGrabContext *c = s->priv_data;
- int size = c->frame_size + AV_INPUT_BUFFER_PADDING_SIZE;
+ shmdt(data);
+}
+
+static AVBufferRef *allocate_shm_buffer(void *opaque, int size)
+{
+ xcb_connection_t *conn = opaque;
+ xcb_shm_seg_t segment;
+ AVBufferRef *ref;
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);
- av_strerror(err, errbuf, sizeof(errbuf));
- av_log(s, AV_LOG_ERROR, "Cannot get %d bytes of shared memory: %s.\n",
- size, errbuf);
- return err;
- }
- xcb_shm_attach(c->conn, c->segment, id, 0);
+ if (id == -1)
+ return NULL;
+
+ segment = xcb_generate_id(conn);
+ xcb_shm_attach(conn, 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;
+ return NULL;
+
+ ref = av_buffer_create(data, size, free_shm_buffer, (void
*)(ptrdiff_t)segment, 0);
+ if (!ref)
+ shmdt(data);
+
+ return ref;
}
static int xcbgrab_frame_shm(AVFormatContext *s, AVPacket *pkt)
@@ -265,15 +267,19 @@ static int xcbgrab_frame_shm(AVFormatContext *s, AVPacket
*pkt)
xcb_shm_get_image_reply_t *img;
xcb_drawable_t drawable = c->screen->root;
xcb_generic_error_t *e = NULL;
- int ret;
+ AVBufferRef *buf;
+ xcb_shm_seg_t segment;
- ret = allocate_shm(s);
- if (ret < 0)
- return ret;
+ buf = av_buffer_pool_get(c->shm_pool);
+ if (!buf) {
+ av_log(s, AV_LOG_ERROR, "Could not get shared memory buffer.\n");
+ return AVERROR(ENOMEM);
+ }
+ segment = (xcb_shm_seg_t)av_buffer_pool_buffer_get_opaque(buf);
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_IMAGE_FORMAT_Z_PIXMAP, segment, 0);
img = xcb_shm_get_image_reply(c->conn, iq, &e);
xcb_flush(c->conn);
@@ -287,12 +293,16 @@ static int xcbgrab_frame_shm(AVFormatContext *s, AVPacket
*pkt)
e->sequence, e->resource_id, e->minor_code, e->major_code);
free(e);
+ av_buffer_unref(&buf);
return AVERROR(EACCES);
}
free(img);
- pkt->data = c->buffer;
+ av_init_packet(pkt);
+
+ pkt->buf = buf;
+ pkt->data = buf->data;
pkt->size = c->frame_size;
return 0;
@@ -425,8 +435,10 @@ 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 && xcbgrab_frame_shm(s, pkt) < 0) {
+ av_log(s, AV_LOG_WARNING, "Continuing without shared memory.\n");
c->has_shm = 0;
+ }
#endif
if (!c->has_shm)
ret = xcbgrab_frame(s, pkt);
@@ -447,9 +459,7 @@ static av_cold int xcbgrab_read_close(AVFormatContext *s)
XCBGrabContext *ctx = s->priv_data;
#if CONFIG_LIBXCB_SHM
- if (ctx->buffer) {
- shmdt(ctx->buffer);
- }
+ av_buffer_pool_uninit(&ctx->shm_pool);
#endif
xcb_disconnect(ctx->conn);
@@ -515,6 +525,12 @@ static int pixfmt_from_pixmap_format(AVFormatContext *s,
int depth,
if (*pix_fmt) {
c->bpp = fmt->bits_per_pixel;
c->frame_size = c->width * c->height * fmt->bits_per_pixel / 8;
+#if CONFIG_LIBXCB_SHM
+ c->shm_pool = av_buffer_pool_init2(c->frame_size +
AV_INPUT_BUFFER_PADDING_SIZE,
+ c->conn, allocate_shm_buffer,
NULL);
