Add a LUT parameter to producer_avformat

[bmatherly]

This parameter allows the application to specify a 3d lut file to be applied to the source.

[ddennedy]

Explain the purpose when there is already avfilter and a filtergraph property on the producer.
What happens when using hwaccel?

[Copilot]

Pull request overview

This PR adds support for applying a 3D LUT to video decoded by the avformat producer by introducing a new lut property that maps to FFmpeg’s lut3d filter.

Changes:

• Bump producer_avformat metadata version and add a new lut parameter in the YAML service definition.
• Extend setup_filters() to optionally insert a lut3d filter (with escaped file path) into the video filter chain.
• Rebuild the video filter graph when the lut property changes, and ensure filter setup is triggered when lut is present.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/modules/avformat/producer_avformat.yml	Adds the lut parameter to the avformat producer’s public parameter schema and bumps the module version.
src/modules/avformat/producer_avformat.c	Implements LUT handling by inserting lut3d into the filter chain and rebuilding filters on property changes.

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[bmatherly]

Explain the purpose when there is already avfilter and a filtergraph property on the producer.

The filter needs to be added precisely before the linear color conversion as observed here:
https://forum.shotcut.org/t/using-lut-on-nikon-n-log-footage-gives-very-dark-output/50927

If I use the filtergraph property, then we would also have to use that for rotate.

What happens when using hwaccel?

I was hoping you would have advice about that before I dig into it too deep.

Also see here:
mltframework/shotcut#1809

[ddennedy]

Regarding hwaccel, I think it will work; just checking if you tested that. I tried, but just a basic test like this fails:
melt -verbose ~/Videos/my.mp4 lut='MOONRISE KINGDOM I.cube' in=6100

Thread 1 "melt" received signal SIGSEGV, Segmentation fault.
0x00007ffff1cf0942 in setup_video_filters (self=0x5555561e8400) at /home/ddennedy/src/mlt/src/modules/avformat/producer_avformat.c:1285
1285	    AVStream *stream = format->streams[self->video_index];
(gdb) where
#0  0x00007ffff1cf0942 in setup_video_filters (self=0x5555561e8400)
    at /home/ddennedy/src/mlt/src/modules/avformat/producer_avformat.c:1285
#1  0x00007ffff1cf1110 in setup_filters (self=0x5555561e8400)
    at /home/ddennedy/src/mlt/src/modules/avformat/producer_avformat.c:1400
#2  0x00007ffff1cf37fb in property_changed (owner=0x555556293440, self=0x5555561e8400, name=0x5555562a0280 "lut")
    at /home/ddennedy/src/mlt/src/modules/avformat/producer_avformat.c:2095
#3  0x00007ffff7f85586 in mlt_events_fire
    (self=0x555556293440, id=0x7ffff7fad172 "property-changed", event_data=...)
    at /home/ddennedy/src/mlt/src/framework/mlt_events.c:211
#4  0x00007ffff7f9a6ca in fire_property_changed (self=0x555556293440, name=0x5555562a0280 "lut")
    at /home/ddennedy/src/mlt/src/framework/mlt_properties.c:738
#5  0x00007ffff7f9adca in mlt_properties_set
    (self=0x555556293440, name=0x5555562a0280 "lut", value=0x55555627fc50 "/home/ddennedy/net/media/aws/unsorted/videos/stock/LUTs/MOONRISE KINGDOM I.cube") at /home/ddennedy/src/mlt/src/framework/mlt_properties.c:918
#6  0x00007ffff7f9b25e in mlt_properties_parse
    (self=0x555556293440, namevalue=0x7fffffffe0b4 "lut=/home/ddennedy/net/media/aws/unsorted/videos/stock/LUTs/MOONRISE KINGDOM I.cube") at /home/ddennedy/src/mlt/src/framework/mlt_properties.c:1125
#7  0x00007ffff665fb55 in producer_melt_init
    (profile=0x555555f9f4f0, type=mlt_service_producer_type, id=0x55555555d8d7 "melt", argv=0x7fffffffdca0)
    at /home/ddennedy/src/mlt/src/modules/core/producer_melt.c:425
#8  0x00007ffff7fa49eb in mlt_repository_create
    (self=0x5555555649c0, profile=0x555555f9f4f0, type=mlt_service_producer_type, service=0x55555555d8d7 "melt", input=0x7fffffffdca0) at /home/ddennedy/src/mlt/src/framework/mlt_repository.c:332
#9  0x00007ffff7f8653d in mlt_factory_producer
    (profile=0x555555f9f4f0, service=0x55555555d8d7 "melt", resource=0x7fffffffdca0)
    at /home/ddennedy/src/mlt/src/framework/mlt_factory.c:343
#10 0x000055555555ad60 in main (argc=5, argv=0x7fffffffdc98) at /home/ddennedy/src/mlt/src/melt/melt.c:976
(gdb) p format
$1 = (AVFormatContext *) 0x0

I made a change:

diff --git a/src/modules/avformat/producer_avformat.c b/src/modules/avformat/producer_avformat.c
index d836443b..5029924c 100644
--- a/src/modules/avformat/producer_avformat.c
+++ b/src/modules/avformat/producer_avformat.c
@@ -2087,7 +2087,7 @@ static void property_changed(mlt_service owner, producer_avformat self, char *na
                 mlt_service_unlock(MLT_PRODUCER_SERVICE(self->parent));
             }
         } else if (!strcmp("lut", name)) {
-            if (self->video_index != -1) {
+            if (self->video_index != -1 && self->video_format) {
                 mlt_service_lock(MLT_PRODUCER_SERVICE(self->parent));
                 avfilter_graph_free(&self->vfilter_graph);
                 self->vfilter_in = NULL;

And now it works with hwaccel plus preview scaling (hw-scaler) and rotate.

[bmatherly]

I made a change:

Thanks. The patch works for me and I applied it.