avdevice/xcbgrab: use a buffer pool for shared memory segments

Also by wrapping the SHM buffer in an AVBufferRef we eliminate yet another
possible memcpy improving performance.

Signed-off-by: Marton Balint <cus@passwd.hu>
This commit is contained in:
Marton Balint 2019-12-07 20:41:44 +01:00
parent 16685114d5
commit c991e9cd91

View File

@ -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);
if (!c->shm_pool)
return AVERROR(ENOMEM);
#endif
return 0;
}
@ -680,8 +696,7 @@ static av_cold int xcbgrab_read_header(AVFormatContext *s)
}
#if CONFIG_LIBXCB_SHM
if ((c->has_shm = check_shm(c->conn)))
c->segment = xcb_generate_id(c->conn);
c->has_shm = check_shm(c->conn);
#endif
#if CONFIG_LIBXCB_XFIXES