This is a POC/prototype that aims to enable out of tree filters on
FFmpeg.
Here I name them "extra filters".
It introduces the program `jq` as a new build dependency.
To test it, create a directory, for instance, /tmp/my-shiny-filter/ and
inside it, create the following files:
`filter.json`, with the content:
```
{
"check": "require_pkg_config json json-c json-c/json.h json_c_version_num",
"symbols": ["ff_vf_foo", "ff_vf_bar"]
}
```
`filter.mak`, with the content:
```
OBJS += vf_shiny.o
LIBOBJS += vf_shiny.o
libavfilter/vf_shiny.o:
$(CC) $(EXTRA_FILTER_FLAGS) -c -o $@
$(EXTRA_FILTER_FOO_LOCATION)/vf_shiny.c
```
`vf_shiny.c` file, with the content:
```
#include "libavutil/internal.h"
#include "avfilter.h"
#include
"filters.h"
#include "video.h"
const FFFilter ff_vf_bar = {
.p.name = "bar",
.p.description = NULL_IF_CONFIG_SMALL("Example filter Baz"),
.p.flags = AVFILTER_FLAG_METADATA_ONLY,
FILTER_INPUTS(ff_video_default_filterpad),
FILTER_OUTPUTS(ff_video_default_filterpad),
};
const FFFilter ff_vf_foo = {
.p.name = "foo",
.p.description = NULL_IF_CONFIG_SMALL("Another foo filter"),
.p.flags = AVFILTER_FLAG_METADATA_ONLY,
FILTER_INPUTS(ff_video_default_filterpad),
FILTER_OUTPUTS(ff_video_default_filterpad),
};
```
Then, from the ffmpeg source tree, run configure specifying where the
extra filter is located:
```
./configure --extra-filter=/tmp/my-shiny-filter
make ffplay
```
Now you can use the filters:
```
./ffplay /path/to/file.webm -vf 'foo,baz'
```
What works:
- Building C based filters with no extra dependencies.
- Multiple filters in the same object file.
What does not work:
- The extra filters will not use the same CC flags used to build the
built-in filters as I could get it to work yet.
- Due to the above limitation, you cannot include headers of extra
dependencies, for instance, `json.h` in the example.
- You can pass arbitrary CFLAGS or LDFLAGS in the filter.json file,
but they should be passed only then building/linking `libavfilter`,
instead of other libraries.
What was not implemented:
- I believe it would be useful to check if the license of the filter is
compatible with the license used to build FFmpeg.
- Only extra filters written in C (maybe C++?) are supported for now.
One of my goals is to enable Rust as well.
Signed-off-by: Leandro Santiago <leandrosansi...@gmail.com>
---
.gitignore | 3 ++
configure | 61 ++++++++++++++++++++++++++++++++++++++++
libavfilter/Makefile | 4 +++
libavfilter/allfilters.c | 1 +
4 files changed, 69 insertions(+)
diff --git a/.gitignore b/.gitignore
index 9cfc78b414..4963e90191 100644
--- a/.gitignore
+++ b/.gitignore
@@ -43,3 +43,6 @@
/tools/python/__pycache__/
/libavcodec/vulkan/*.c
/libavfilter/vulkan/*.c
+/ffbuild/extra-filters.txt
+/ffbuild/extra-filters.mak
+/libavfilter/extra_filters_extern.h
diff --git a/configure b/configure
index 750c99e3b9..6a2adc6c05 100755
--- a/configure
+++ b/configure
@@ -179,6 +179,7 @@ Individual component options:
--enable-filter=NAME enable filter NAME
--disable-filter=NAME disable filter NAME
--disable-filters disable all filters
+ --extra-filter=/foo/bar add extra filter from directory. This option can be
used multiple times
External library support:
@@ -1798,6 +1799,7 @@ AVDEVICE_COMPONENTS="
AVFILTER_COMPONENTS="
filters
+ extra_filters
"
AVFORMAT_COMPONENTS="
@@ -4382,6 +4384,8 @@ do_random(){
$action $(rand_list "$@" | awk "BEGIN { srand($random_seed) } \$1 ==
\"prob\" { prob = \$2; next } rand() < prob { print }")
}
+rm -f ffbuild/extra-filters.txt
+
# deprecated components (disabled by default)
disable sonic_encoder sonic_ls_encoder
@@ -4457,6 +4461,10 @@ for opt do
die_unknown $opt
fi
;;
+ --extra-filter=*)
+ filter_path="${opt#--extra-filter=}"
+ echo "$filter_path" >> ffbuild/extra-filters.txt
+ ;;
--list-*)
NAME="${opt#--list-}"
is_in $NAME $COMPONENT_LIST || die_unknown $opt
@@ -4487,6 +4495,36 @@ for opt do
esac
done
+find_extra_filters_extern() {
+ # TODO: handle invalid filter
+ while read f; do
+ jq -r '.symbols[]' < "$f/filter.json" | sed
's/^ff_[avfsinkrc]\{2,5\}_\([[:alnum:]_]\{1,\}\)/\1_filter/'
+ done < ffbuild/extra-filters.txt
+}
+
+EXTRA_FILTER_LIST=$(find_extra_filters_extern)
+
+for n in extra_filters; do
+ v=$(toupper ${n%s})_LIST
+ eval enable \$$v
+ eval ${n}_if_any="\$$v"
+done
+
+FILTER_LIST="
+ $FILTER_LIST
+ $EXTRA_FILTER_LIST
+"
+
+AVFILTER_COMPONENTS_LIST="
+ $AVFILTER_COMPONENTS_LIST
+ $EXTRA_FILTER_LIST
+"
+
+ALL_COMPONENTS="
+ $ALL_COMPONENTS
+ $EXTRA_FILTER_LIST
+"
+
for e in $env; do
eval "export $e"
done
@@ -7165,6 +7203,10 @@ enabled rkmpp && { require_pkg_config rkmpp
rockchip_mpp rockchip/r
}
enabled vapoursynth && require_headers "vapoursynth/VSScript4.h
vapoursynth/VapourSynth4.h"
+while read f; do
+ # NOTE: this eval is dangerous, as it allows arbitrary code execution!
+ eval $(jq -r '.check // true' < "$f/filter.json")
+done < ffbuild/extra-filters.txt
if enabled gcrypt; then
GCRYPT_CONFIG="${cross_prefix}libgcrypt-config"
@@ -8243,6 +8285,12 @@ for entry in $LIBRARY_LIST $PROGRAM_LIST
$EXTRALIBS_LIST; do
eval echo "EXTRALIBS-${entry}=\$${entry}_extralibs" >> ffbuild/config.mak
done
+echo "" > ffbuild/extra-filters.mak
+
+while read f; do
+ echo "include $f/filter.mak" >> ffbuild/extra-filters.mak
+done < ffbuild/extra-filters.txt
+
cat > $TMPH <<EOF
/* Automatically generated by configure - do not modify! */
#ifndef FFMPEG_CONFIG_H
@@ -8330,6 +8378,19 @@ cp_if_changed $TMPH libavutil/avconfig.h
# ...
eval "$(sed -n "s/^extern const FFFilter
ff_\([avfsinkrc]\{2,5\}\)_\(.*\);/full_filter_name_\2=\1_\2/p"
$source_path/libavfilter/allfilters.c)"
+rm -f libavfilter/extra_filters_extern.h
+
+# Handle extra filters
+while read f; do
+ eval "$(jq -r '.symbols[]' < "$f/filter.json" | sed
's/^ff_\([avfsinkrc]\{2,5\}\)_\([[:alnum:]]\{1,\}\)$/full_filter_name_\2=\1_\2/')"
+ jq -r '.symbols[]' < "$f/filter.json" | while read symbol; do
+ echo "extern const FFFilter $symbol;" >>
libavfilter/extra_filters_extern.h
+ echo "EXTRA_FILTER_$(echo $symbol | sed
's/^ff_[avfsinkrc]\{2,5\}_\([[:alnum:]]\{1,\}\)$/\1/' | tr a-z A-Z)_LOCATION =
$f" >> ffbuild/extra-filters.mak
+ echo "LDFLAGS += $(jq -r '.ldflags // ""' < "$f/filter.json")" >>
ffbuild/extra-filters.mak
+ echo "CFLAGS += $(jq -r '.cflags // ""' < "$f/filter.json")" >>
ffbuild/extra-filters.mak
+ done
+done < ffbuild/extra-filters.txt
+
# generate the lists of enabled components
print_enabled_components(){
file=$1
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 7c0d879ec9..9b22aece3a 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -27,6 +27,10 @@ OBJS = allfilters.o
\
include $(SRC_PATH)/libavfilter/dnn/Makefile
include $(SRC_PATH)/libavfilter/vulkan/Makefile
+# extra filters handling
+include $(SRC_PATH)/ffbuild/extra-filters.mak
+EXTRA_FILTER_FLAGS = -I$(PWD) -I$(PWD)/libavfilter $(CPPFLAGS) $(CC_DEPFLAGS)
+
OBJS-$(HAVE_LIBC_MSVCRT) += file_open.o
OBJS-$(HAVE_THREADS) += pthread.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 740d9ab265..e8565de5b0 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -621,6 +621,7 @@ extern const FFFilter ff_vsrc_buffer;
extern const FFFilter ff_asink_abuffer;
extern const FFFilter ff_vsink_buffer;
+#include "libavfilter/extra_filters_extern.h"
#include "libavfilter/filter_list.c"
--
2.48.1
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