[FFmpeg-devel] [PATCH] avdevice/xcbgrab: Improve non-shm performance

[Kusanagi Kouichi]

Use AVBufferPool.

before:
$ ffmpeg -benchmark -f x11grab -video_size 1920x1200 -r 200 -t 3 -i +0,0 -f null -
...
frame=  600 fps=102 q=-0.0 Lsize=N/A time=00:00:03.00 bitrate=N/A speed=0.51x
video:314kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
bench: utime=1.551s stime=3.428s rtime=5.884s
bench: maxrss=40132kB

after:
$ ffmpeg -benchmark -f x11grab -video_size 1920x1200 -r 200 -t 3 -i +0,0 -f null -
...
frame=  600 fps=138 q=-0.0 Lsize=N/A time=00:00:03.00 bitrate=N/A speed=0.69x
video:314kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
bench: utime=1.231s stime=2.407s rtime=4.349s
bench: maxrss=40096kB

Signed-off-by: Kusanagi Kouichi <slash at ac.auone-net.jp>
---
 libavdevice/xcbgrab.c | 38 +++++++++++++++++++++++++++++++-------
 1 file changed, 31 insertions(+), 7 deletions(-)

diff --git a/libavdevice/xcbgrab.c b/libavdevice/xcbgrab.c
index b7e689343e..fde9c534cd 100644
--- a/libavdevice/xcbgrab.c
+++ b/libavdevice/xcbgrab.c
@@ -42,6 +42,7 @@
 #include "libavutil/opt.h"
 #include "libavutil/parseutils.h"
 #include "libavutil/time.h"
+#include "libavutil/buffer.h"
 
 #include "libavformat/avformat.h"
 #include "libavformat/internal.h"
@@ -71,6 +72,8 @@ typedef struct XCBGrabContext {
     int region_border;
     int centered;
 
+    AVBufferPool *buf_pool;
+
     const char *video_size;
     const char *framerate;
 
@@ -146,6 +149,16 @@ static int xcbgrab_reposition(AVFormatContext *s,
     return 0;
 }
 
+static AVBufferRef *xcbgrab_allocate_buffer(const int size)
+{
+    AVPacket pkt;
+
+    if (av_new_packet(&pkt, size))
+        return NULL;
+
+    return pkt.buf;
+}
+
 static int xcbgrab_frame(AVFormatContext *s, AVPacket *pkt)
 {
     XCBGrabContext *c = s->priv_data;
@@ -154,7 +167,7 @@ static int xcbgrab_frame(AVFormatContext *s, AVPacket *pkt)
     xcb_drawable_t drawable = c->screen->root;
     xcb_generic_error_t *e = NULL;
     uint8_t *data;
-    int length, ret;
+    int length;
 
     iq  = xcb_get_image(c->conn, XCB_IMAGE_FORMAT_Z_PIXMAP, drawable,
                         c->x, c->y, c->width, c->height, ~0);
@@ -174,17 +187,21 @@ static int xcbgrab_frame(AVFormatContext *s, AVPacket *pkt)
     if (!img)
         return AVERROR(EAGAIN);
 
+    pkt->buf = av_buffer_pool_get(c->buf_pool);
+    if (!pkt->buf) {
+        free(img);
+        return AVERROR(ENOMEM);
+    }
+
     data   = xcb_get_image_data(img);
     length = xcb_get_image_data_length(img);
 
-    ret = av_new_packet(pkt, length);
-
-    if (!ret)
-        memcpy(pkt->data, data, length);
-
+    memcpy(pkt->buf->data, data, length);
     free(img);
+    pkt->data = pkt->buf->data;
+    pkt->size = pkt->buf->size;
 
-    return ret;
+    return 0;
 }
 
 static void wait_frame(AVFormatContext *s, AVPacket *pkt)
@@ -442,6 +459,7 @@ static av_cold int xcbgrab_read_close(AVFormatContext *s)
 #endif
 
     xcb_disconnect(ctx->conn);
+    av_buffer_pool_uninit(&ctx->buf_pool);
 
     return 0;
 }
@@ -665,6 +683,12 @@ static av_cold int xcbgrab_read_header(AVFormatContext *s)
         return ret;
     }
 
+    c->buf_pool = av_buffer_pool_init(c->frame_size, xcbgrab_allocate_buffer);
+    if (ret < 0) {
+        xcbgrab_read_close(s);
+        return AVERROR(ENOMEM);
+    }
+
 #if CONFIG_LIBXCB_SHM
     if ((c->has_shm = check_shm(c->conn)))
         c->segment = xcb_generate_id(c->conn);
-- 
2.24.0