hwdec_drmprime: try and declare support for weird forked ffmpeg formats

As a result of the work I did the explicitly check for formats
supported by the vo in the f_autoconvert logic, I introduced a
regression in the handling of the rpi4_8 and rpi4_10 formats. These
require special handling because they only exist in the rpi forks and
not upstream ffmpeg, which means they don't have stable pix fmt values
that we can use directly.

Previously, we simply didn't declare them as supported, which was ok,
as nothing was really enforcing the list of supported formats, but that
has changed.

As we still can't simply use the pix fmts, I had to do a slightly
ridiculous dance to look them up by name, and if they exist, then
register them as supported.

Good times.

1 files changed, 21 insertions, 0 deletions

diff --git a/video/out/hwdec/hwdec_drmprime.c b/video/out/hwdec/hwdec_drmprime.c
index f7c6250cb6..a5f9c664fb 100644
--- a/video/out/hwdec/hwdec_drmprime.c
+++ b/video/out/hwdec/hwdec_drmprime.c
@@ -23,6 +23,7 @@
 
 #include <libavutil/hwcontext.h>
 #include <libavutil/hwcontext_drm.h>
+#include <libavutil/pixdesc.h>
 #include <xf86drm.h>
 
 #include "config.h"
@@ -64,6 +65,18 @@ const static dmabuf_interop_init interop_inits[] = {
     NULL
 };
 
+/**
+ * Due to the fact that Raspberry Pi support only exists in forked ffmpegs and
+ * also requires custom pixel formats, we need some way to work with those formats
+ * without introducing any build time dependencies. We do this by looking up the
+ * pixel formats by name. As rpi is an important target platform for this hwdec
+ * we don't really have the luxury of ignoring these forks.
+ */
+const static char *forked_pix_fmt_names[] = {
+    "rpi4_8",
+    "rpi4_10",
+};
+
 static int init(struct ra_hwdec *hw)
 {
     struct priv_owner *p = hw->priv;
@@ -119,6 +132,14 @@ static int init(struct ra_hwdec *hw)
     MP_TARRAY_APPEND(p, p->formats, num_formats, IMGFMT_NV12);
     MP_TARRAY_APPEND(p, p->formats, num_formats, IMGFMT_420P);
     MP_TARRAY_APPEND(p, p->formats, num_formats, pixfmt2imgfmt(AV_PIX_FMT_NV16));
+
+    for (int i = 0; i < MP_ARRAY_SIZE(forked_pix_fmt_names); i++) {
+        enum AVPixelFormat fmt = av_get_pix_fmt(forked_pix_fmt_names[i]);
+        if (fmt != AV_PIX_FMT_NONE) {
+            MP_TARRAY_APPEND(p, p->formats, num_formats, pixfmt2imgfmt(fmt));
+        }
+    }
+
     MP_TARRAY_APPEND(p, p->formats, num_formats, 0); // terminate it
 
     p->hwctx.hw_imgfmt = IMGFMT_DRMPRIME;