vd_lavc: add "auto" choice for vd-lavc-dr

--vd-lavc-dr defaulted to "yes", which caused issues on certain
hardware. Instead of disabling it, add a new "auto" value and
make it the default.

The "auto" choice will enable DR only when we can request host-cached
buffers (as signalled by the new VO_DR_FLAG_HOST_CACHED).

Co-authored-by: Nicolas F. <ovdev@fratti.ch>
Co-authored-by: Niklas Haas <git@haasn.dev>

4 files changed, 21 insertions, 6 deletions

diff --git a/DOCS/interface-changes.rst b/DOCS/interface-changes.rst
index 7bbbfd5a0c..875fce4b5a 100644
--- a/DOCS/interface-changes.rst
+++ b/DOCS/interface-changes.rst
@@ -26,6 +26,9 @@ Interface changes
 
 ::
 
+=======
+ --- mpv 0.35.1 --- (feature backport due to special circumstances)
+    - add `--vd-lavc-dr=auto` and make it the default
  --- mpv 0.35.0 ---
     - add the `--vo=gpu-next` video output driver, as well as the options
       `--allow-delayed-peak-detect`, `--builtin-scalers`,
diff --git a/DOCS/man/options.rst b/DOCS/man/options.rst
index 9b7908eaec..3d7dc16831 100644
--- a/DOCS/man/options.rst
+++ b/DOCS/man/options.rst
@@ -1701,8 +1701,8 @@ Video
     support this, then it will be treated as ``cpu``, regardless of the setting.
     Currently, only ``gpu-next`` supports film grain application.
 
-``--vd-lavc-dr=<yes|no>``
-    Enable direct rendering (default: yes). If this is set to ``yes``, the
+``--vd-lavc-dr=<auto|yes|no>``
+    Enable direct rendering (default: auto). If this is set to ``yes``, the
     video will be decoded directly to GPU video memory (or staging buffers).
     This can speed up video upload, and may help with large resolutions or
     slow hardware. This works only with the following VOs:
@@ -1710,6 +1710,10 @@ Video
         - ``gpu``: requires at least OpenGL 4.4 or Vulkan.
         - ``libmpv``: The libmpv render API has optional support.
 
+    The ``auto`` option will try to guess whether DR can improve performance
+    on your particular hardware. Currently this enables it on AMD or NVIDIA
+    if using OpenGL or unconditionally if using Vulkan.
+
     Using video filters of any kind that write to the image data (or output
     newly allocated frames) will silently disable the DR code path.
 
diff --git a/video/decode/vd_lavc.c b/video/decode/vd_lavc.c
index d3bdc3c09e..cc8f7bb1b5 100644
--- a/video/decode/vd_lavc.c
+++ b/video/decode/vd_lavc.c
@@ -119,7 +119,8 @@ const struct m_sub_options vd_lavc_conf = {
         {"vd-lavc-software-fallback", OPT_CHOICE(software_fallback,
             {"no", INT_MAX}, {"yes", 1}), M_RANGE(1, INT_MAX)},
         {"vd-lavc-o", OPT_KEYVALUELIST(avopts)},
-        {"vd-lavc-dr", OPT_FLAG(dr)},
+        {"vd-lavc-dr", OPT_CHOICE(dr,
+            {"auto", -1}, {"no", 0}, {"yes", 1})},
         {"hwdec", OPT_STRING(hwdec_api),
             .help = hwdec_opt_help,
             .flags = M_OPT_OPTIONAL_PARAM | UPDATE_HWDEC},
@@ -138,7 +139,7 @@ const struct m_sub_options vd_lavc_conf = {
         .skip_idct = AVDISCARD_DEFAULT,
         .skip_frame = AVDISCARD_DEFAULT,
         .framedrop = AVDISCARD_NONREF,
-        .dr = 1,
+        .dr = -1,
         .hwdec_api = "no",
         .hwdec_codecs = "h264,vc1,hevc,vp8,vp9,av1,prores",
         // Maximum number of surfaces the player wants to buffer. This number
@@ -967,8 +968,10 @@ static int get_buffer2_direct(AVCodecContext *avctx, AVFrame *pic, int flags)
 
     struct mp_image *img = mp_image_pool_get_no_alloc(p->dr_pool, imgfmt, w, h);
     if (!img) {
-        MP_DBG(p, "Allocating new DR image...\n");
-        img = vo_get_image(p->vo, imgfmt, w, h, stride_align, 0);
+        bool host_cached = p->opts->dr == -1; // auto
+        int dr_flags = host_cached ? VO_DR_FLAG_HOST_CACHED : 0;
+        MP_DBG(p, "Allocating new%s DR image...\n", host_cached ? " (host-cached)" : "");
+        img = vo_get_image(p->vo, imgfmt, w, h, stride_align, dr_flags);
         if (!img) {
             MP_DBG(p, "...failed..\n");
             goto fallback;
diff --git a/video/out/vo.h b/video/out/vo.h
index f176bee59f..1c170cafb6 100644
--- a/video/out/vo.h
+++ b/video/out/vo.h
@@ -184,6 +184,11 @@ enum {
     VO_CAP_FILM_GRAIN   = 1 << 3,
 };
 
+enum {
+    // Require DR buffers to be host-cached (i.e. fast readback)
+    VO_DR_FLAG_HOST_CACHED = 1 << 0,
+};
+
 #define VO_MAX_REQ_FRAMES 10
 
 struct vo;