diff options
authorwm4 <wm4@nowhere>2020-02-07 13:32:07 +0100
committerwm4 <wm4@nowhere>2020-02-07 13:32:21 +0100
commita3bd8c3b5f84c5d48785552fc7bd2505ee839736 (patch)
parent3d17e19c2c5ca80f916411e7e61126cac8443baa (diff)
player: make screenshot each-frame mode more accurate
Due to asynchronicity, we generally can't guarantee that a video frame matches up with other events such as playback time change exactly (since decoding, presentation, and property update all happen at different times). This is a complaint in the referenced bug report, where screenshot filenames in each-frame screenshot did not use the correct timestamp, and instead was lagging behind by 1 frame. But in this case, synchronicity was already pretty much forced with wait calls. The only problem was that the playback time was updated at a later time, which results in the observed 1 frame lag. Fix this by moving the place where the screenshot is triggered in this mode. Normal screenshots may still have the old problem. There is no effort made to guarantee the timestamps absolutely line up, same as with the OSD. (If you want a guarantee, you need to use a video filter, such as libavfilter's drawtext. These will obviously use the proper timestamp, instead of going through the somewhat asynchronous property etc. system in the player frontend.) Fixes: #7433
4 files changed, 11 insertions, 5 deletions
diff --git a/player/playloop.c b/player/playloop.c
index 7b5a2f6d45..86f19fd79f 100644
--- a/player/playloop.c
+++ b/player/playloop.c
@@ -49,6 +49,7 @@
#include "core.h"
#include "client.h"
#include "command.h"
+#include "screenshot.h"
// Wait until mp_wakeup_core() is called, since the last time
// mp_wait_events() was called.
@@ -1226,6 +1227,8 @@ void run_playloop(struct MPContext *mpctx)
if (mpctx->video_status == STATUS_EOF)
update_subtitles(mpctx, mpctx->playback_pts);
+ handle_each_frame_screenshot(mpctx);
diff --git a/player/screenshot.c b/player/screenshot.c
index eccce16dd6..5651b1b7ec 100644
--- a/player/screenshot.c
+++ b/player/screenshot.c
@@ -53,6 +53,7 @@ typedef struct screenshot_ctx {
struct mp_cmd *each_frame;
int frameno;
+ uint64_t last_frame_count;
} screenshot_ctx;
void screenshot_init(struct MPContext *mpctx)
@@ -529,13 +530,17 @@ static void screenshot_fin(struct mp_cmd_ctx *cmd)
-void screenshot_flip(struct MPContext *mpctx)
+void handle_each_frame_screenshot(struct MPContext *mpctx)
screenshot_ctx *ctx = mpctx->screenshot_ctx;
if (!ctx->each_frame)
+ if (ctx->last_frame_count == mpctx->shown_vframes)
+ return;
+ ctx->last_frame_count = mpctx->shown_vframes;
struct mp_waiter wait = MP_WAITER_INITIALIZER;
void *a[] = {mpctx, &wait};
run_command(mpctx, mp_cmd_clone(ctx->each_frame), NULL, screenshot_fin, a);
diff --git a/player/screenshot.h b/player/screenshot.h
index 990cb9503b..97abc79bde 100644
--- a/player/screenshot.h
+++ b/player/screenshot.h
@@ -28,8 +28,8 @@ struct mpv_global;
// One time initialization at program start.
void screenshot_init(struct MPContext *mpctx);
-// Called by the playback core code when a new frame is displayed.
-void screenshot_flip(struct MPContext *mpctx);
+// Called by the playback core on each iteration.
+void handle_each_frame_screenshot(struct MPContext *mpctx);
/* Return the image converted to the given format. If the pixel aspect ratio is
* not 1:1, the image is scaled as well. Returns NULL on failure.
diff --git a/player/video.c b/player/video.c
index e92aaf7024..d8b7728fe8 100644
--- a/player/video.c
+++ b/player/video.c
@@ -1224,8 +1224,6 @@ void write_video(struct MPContext *mpctx)
vo_c->underrun_signaled = false;
- screenshot_flip(mpctx);