fix(gstreamer): prevent memory leak when updating video frames by mn89h · Pull Request #9768 · lvgl/lvgl

mn89h · 2026-02-24T16:40:33Z

Reuse a persistent image descriptor and pixel buffer instead of creating a new image source each frame. This prevents repeated texture allocations (notably on OpenGL).

cubic-dev-ai

No issues found across 2 files

github-actions · 2026-02-24T16:46:29Z

Hi 👋, thank you for your PR!

We've run benchmarks in an emulated environment. Here are the results:

ARM Emulated 32b - lv_conf_perf32b

Scene Name	Avg CPU (%)	Avg FPS	Avg Time (ms)	Render Time (ms)	Flush Time (ms)
All scenes avg.	29	37	7	7	0

Detailed Results Per Scene

Scene Name	Avg CPU (%)	Avg FPS	Avg Time (ms)	Render Time (ms)
Empty screen	11	33	0	0
Moving wallpaper	2	33	1	1
Single rectangle	0	50	0	0
Multiple rectangles	0	33	0	0
Multiple RGB images	0	39	0	0
Multiple ARGB images	11	39 (-1)	3	3
Rotated ARGB images	55 (+1)	44	15	15
Multiple labels	7	35	0	0
Screen sized text	97	47	20	20
Multiple arcs	33	33	7	7
Containers	1 (+1)	37	0	0
Containers with overlay	98	21	44	44
Containers with opa	18	38	1	1
Containers with opa_layer	18 (-1)	33 (-1)	6	6
Containers with scrolling	44	45	12	12
Widgets demo	72	39	17	17
All scenes avg.	29	37	7	7

ARM Emulated 64b - lv_conf_perf64b

Scene Name	Avg CPU (%)	Avg FPS	Avg Time (ms)	Render Time (ms)	Flush Time (ms)
All scenes avg.	25	37	6	6	0

Detailed Results Per Scene

Scene Name	Avg CPU (%)	Avg FPS	Avg Time (ms)	Render Time (ms)
Empty screen	11	33	0	0
Moving wallpaper	1	33	0	0
Single rectangle	0	50	0	0
Multiple rectangles	0	35	0	0
Multiple RGB images	0	39	0	0
Multiple ARGB images	11	42	0	0
Rotated ARGB images	29	33	9	9
Multiple labels	2	35	0	0
Screen sized text	84	46	18	18
Multiple arcs	40	33	6	6
Containers	4	37	0	0
Containers with overlay	88 (-1)	23 (+1)	41	41
Containers with opa	14	38 (+2)	1 (+1)	1 (+1)
Containers with opa_layer	9 (+2)	36 (-1)	2 (+1)	2 (+1)
Containers with scrolling	48 (+1)	48	12	12
Widgets demo	68	40	15	15
All scenes avg.	25	37	6	6

Disclaimer: These benchmarks were run in an emulated environment using QEMU with instruction counting mode.
The timing values represent relative performance metrics within this specific virtualized setup and should
not be interpreted as absolute real-world performance measurements. Values are deterministic and useful for
comparing different LVGL features and configurations, but may not correlate directly with performance on
physical hardware. The measurements are intended for comparative analysis only.

🤖 This comment was automatically generated by a bot.

Reuse a persistent image descriptor and pixel buffer instead of creating a new image source each frame. This prevents repeated texture allocations (notably on OpenGL).

AndreCostaaa

Hey Malte, what is the motivation for this change?

mn89h · 2026-02-27T10:54:22Z

Hi Andre :) I had the problem of memory leaks with GStreamer in conjunction with OpenGLES. It fixes two things: first, it stops the GLES backend from constantly allocating and leaking new textures in VRAM. Since I'm now reusing a persistent pixel buffer and only calling lv_image_set_src once, the renderer can just update the existing texture in-place instead of creating a new one X times a second.
The second thing is a quick drain for the frame queue. If the UI thread lagged behind the video's framerate, that async queue would keep growing infinitely with unrendered GstSamples.

- check for current state and return if no update needed - wait for pipeline transitioning before start freeing memory - drop image cache before freeing pixel buffer and on resolution change

mn89h · 2026-02-27T13:15:26Z

I have discovered some more things, especially in caps handling after first frame, as well as some memory related stuff. In my tests it seems stable now, especially with many state changes after longer periods, where i would repeatedly get crashes.

- update caps not only on first_frame, but also on changes (e.g. resolution) - added null check when pad is added

AndreCostaaa · 2026-03-02T08:06:20Z

The second thing is a quick drain for the frame queue. If the UI thread lagged behind the video's framerate, that async queue would keep growing infinitely with unrendered GstSamples.

The pipeline is configured to send a frame every LV_DEF_REFR_PERIOD and internally we're fetching a sample every LV_DEF_REFR_PERIOD / 5 ms

Is the lag caused by a huge render time/flush time ?

AndreCostaaa

I'm of the opinion we need to figure something else out for the frame updating part of the PR

What you're going for is the original implementation of gstreamer but it relies on copying each frame which is slow and not necessary, it was updated afterwards to avoid the memcpy. Specially if the problem is with draw opengles, I believe we need to figure something else with it.

Also note that for LVGL v9.5 I recommend using DRAW_NANOVG instead of DRAW_OPENGLES

I'll take a look at it as well

I like the other changes tho, can we split these into different PRs?

AndreCostaaa · 2026-03-02T08:08:18Z

src/libs/gstreamer/lv_gstreamer.c

+
+        if(streamer->pixel_buffer) {
+            lv_image_cache_drop(&streamer->frame);
+            free(streamer->pixel_buffer);


Suggested change

free(streamer->pixel_buffer);

lv_free(streamer->pixel_buffer);

Or better yet, what about using realloc instead of free + malloc?

AndreCostaaa · 2026-03-02T08:14:27Z

src/libs/gstreamer/lv_gstreamer.c

+    }
+
+    /* Copy new pixels */
+    memcpy(streamer->pixel_buffer, map.data, required_size);


Suggested change

memcpy(streamer->pixel_buffer, map.data, required_size); lv_memcpy(streamer->pixel_buffer, map.data, required_size);

This is a blocker for the PR, memcpying each frame is something we want to avoid, it will make gstreamer slower for everyone that is not using draw_opengles

AndreCostaaa · 2026-03-02T08:15:50Z

src/libs/gstreamer/lv_gstreamer.c

+
+    /* Copy new pixels */
+    memcpy(streamer->pixel_buffer, map.data, required_size);
+    if(!streamer->image_src_set) {


I guess we can get rid of this image_src_set attribute and instead just move lv_image_set_src inside the

streamer->pixel_buffer == NULL || streamer->pixel_buffer_size != required_size condition

AndreCostaaa · 2026-03-02T08:19:33Z

src/libs/gstreamer/lv_gstreamer.c

+    if(streamer->pixel_buffer) {
+        /* Drop the image from cache before freeing the buffer */
+        lv_image_cache_drop(&streamer->frame);
+        free(streamer->pixel_buffer);


Suggested change

free(streamer->pixel_buffer);

lv_free(streamer->pixel_buffer);

mn89h requested a review from AndreCostaaa as a code owner February 24, 2026 16:40

cubic-dev-ai bot reviewed Feb 24, 2026

View reviewed changes

fix(gstreamer): prevent memory leak when updating video frames

a70d132

Reuse a persistent image descriptor and pixel buffer instead of creating a new image source each frame. This prevents repeated texture allocations (notably on OpenGL).

mn89h force-pushed the fix-gstreamer-memory branch from 5a1af6b to a70d132 Compare February 25, 2026 09:35

AndreCostaaa reviewed Feb 26, 2026

View reviewed changes

fix(gstreamer): state change guards and synchronous destruction

ac4c41a

- check for current state and return if no update needed - wait for pipeline transitioning before start freeing memory - drop image cache before freeing pixel buffer and on resolution change

mn89h force-pushed the fix-gstreamer-memory branch from f449e4e to ac20d4b Compare February 27, 2026 13:17

fix(gstreamer): dynamic caps update and add null check

47fb81f

- update caps not only on first_frame, but also on changes (e.g. resolution) - added null check when pad is added

mn89h force-pushed the fix-gstreamer-memory branch from ac20d4b to 47fb81f Compare February 27, 2026 13:19

AndreCostaaa requested changes Mar 2, 2026

View reviewed changes

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fix(gstreamer): prevent memory leak when updating video frames#9768

fix(gstreamer): prevent memory leak when updating video frames#9768
mn89h wants to merge 3 commits intolvgl:masterfrom
mn89h:fix-gstreamer-memory

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	free(streamer->pixel_buffer);
	lv_free(streamer->pixel_buffer);

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ARM Emulated 32b - lv_conf_perf32b

ARM Emulated 64b - lv_conf_perf64b

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