Commit 6f069e52 for guacamole.apache.org
commit 6f069e524e785f432b3f3575a600480f4cfce0a4
Author: kakwa <carpentier.pf@gmail.com>
Date: Fri Oct 23 14:40:10 2026 +0200
GUACAMOLE-2349: use frame duration to reduce guacenc output size.
With newer ffmpeg/libavutil versions, leverage frame duration to avoid
pushing the same frame over and over again.
Instead use the guac duration (capped at 65535) to set the libav frame
duration.
This drastically reduces the outpout video file size and encoding time
in case of long periods of inactivities within the recording.
diff --git a/src/guacenc/video.c b/src/guacenc/video.c
index cd7fcfc9..9533afd3 100644
--- a/src/guacenc/video.c
+++ b/src/guacenc/video.c
@@ -191,10 +191,10 @@ fail_codec:
/**
* Flushes the specified frame as a new frame of video, updating the internal
- * video timestamp by one frame's worth of time. The pts member of the given
- * frame structure will be updated with the current presentation timestamp of
- * the video. If pending frames of the video are being flushed, the given frame
- * may be NULL (as required by avcodec_encode_video2()).
+ * video timestamp by the given duration. The pts member of the given frame
+ * structure will be updated with the current presentation timestamp of the
+ * video. If pending frames of the video are being flushed, the given frame may
+ * be NULL (as required by avcodec_encode_video2()).
*
* @param video
* The video to write the given frame to.
@@ -203,16 +203,28 @@ fail_codec:
* The frame to write to the video, or NULL if previously-written frames
* are being flushed.
*
+ * @param duration
+ * The duration for which the frame should be displayed, in units of the
+ * video time base (one unit being one frame's worth of time at the
+ * configured framerate). The internal video timestamp will be advanced by
+ * this amount.
+ *
* @return
* A positive value if the frame was successfully written, zero if the
* frame has been saved for later writing / reordering, negative if an
* error occurs.
*/
-static int guacenc_video_write_frame(guacenc_video* video, AVFrame* frame) {
+static int guacenc_video_write_frame(guacenc_video* video, AVFrame* frame,
+ int64_t duration) {
- /* Set timestamp of frame, if frame given */
- if (frame != NULL)
+ /* Set timestamp and display duration of frame, if frame given */
+ if (frame != NULL) {
frame->pts = video->next_pts;
+#if LIBAVUTIL_VERSION_INT < AV_VERSION_INT(56,14,100)
+#else
+ frame->duration = duration;
+#endif
+ }
/* Write frame to video */
int got_data = guacenc_avcodec_encode_video(video, frame);
@@ -220,7 +232,7 @@ static int guacenc_video_write_frame(guacenc_video* video, AVFrame* frame) {
return -1;
/* Update presentation timestamp for next frame */
- video->next_pts++;
+ video->next_pts += duration;
/* Write was successful */
return got_data;
@@ -229,19 +241,24 @@ static int guacenc_video_write_frame(guacenc_video* video, AVFrame* frame) {
/**
* Flushes the frame previously specified by guacenc_video_prepare_frame() as a
- * new frame of video, updating the internal video timestamp by one frame's
- * worth of time.
+ * new frame of video, updating the internal video timestamp by the given
+ * duration.
*
* @param video
* The video to flush.
*
+ * @param duration
+ * The duration for which the flushed frame should be displayed, in units
+ * of the video time base (one unit being one frame's worth of time at the
+ * configured framerate).
+ *
* @return
* Zero if flushing was successful, non-zero if an error occurs.
*/
-static int guacenc_video_flush_frame(guacenc_video* video) {
+static int guacenc_video_flush_frame(guacenc_video* video, int64_t duration) {
/* Write frame to video */
- return guacenc_video_write_frame(video, video->next_frame) < 0;
+ return guacenc_video_write_frame(video, video->next_frame, duration) < 0;
}
@@ -265,14 +282,37 @@ int guacenc_video_advance_timeline(guacenc_video* video,
next_timestamp = video->last_timestamp
+ elapsed * 1000 / GUACENC_VIDEO_FRAMERATE;
+#if LIBAVUTIL_VERSION_INT < AV_VERSION_INT(56,14,100)
/* Flush frames to bring timeline in sync, duplicating if necessary */
do {
- if (guacenc_video_flush_frame(video)) {
+ if (guacenc_video_flush_frame(video, 1)) {
guacenc_log(GUAC_LOG_ERROR, "Unable to flush frame to video "
"stream.");
return 1;
}
} while (--elapsed != 0);
+#else
+ /* Instead of encoding the same frame once per elapsed tick, encode it
+ * with an extended display duration covering the gap, clamping each
+ * frame's duration such that the codec can actually represent the
+ * requested gap (some codecs, such as MPEG-4, cannot encode a single
+ * frame with an arbitrarily long display duration). If the gap exceeds
+ * that limit, duplicate frames are encoded to cover the remainder. */
+ int64_t remaining = elapsed;
+ do {
+ int64_t duration = remaining;
+ if (duration > GUACENC_MAX_FRAME_DURATION)
+ duration = GUACENC_MAX_FRAME_DURATION;
+
+ if (guacenc_video_flush_frame(video, duration)) {
+ guacenc_log(GUAC_LOG_ERROR, "Unable to flush frame to video "
+ "stream.");
+ return 1;
+ }
+
+ remaining -= duration;
+ } while (remaining > 0);
+#endif
}
@@ -472,12 +512,12 @@ int guacenc_video_free(guacenc_video* video) {
return 0;
/* Write final frame */
- guacenc_video_flush_frame(video);
+ guacenc_video_flush_frame(video, 1);
/* Flush any unwritten frames */
int retval;
do {
- retval = guacenc_video_write_frame(video, NULL);
+ retval = guacenc_video_write_frame(video, NULL, 1);
} while (retval > 0);
/* write trailer, if needed */
diff --git a/src/guacenc/video.h b/src/guacenc/video.h
index 596366a2..56415f98 100644
--- a/src/guacenc/video.h
+++ b/src/guacenc/video.h
@@ -41,6 +41,12 @@
*/
#define GUACENC_VIDEO_FRAMERATE 25
+/**
+ * The maximum duration of a frame
+ */
+#define GUACENC_MAX_FRAME_DURATION 65535
+
+
/**
* A video which is actively being encoded. Frames can be added to the video
* as they are generated, along with their associated timestamps, and the