vd_lavc: more hwdec autoselect nonsense

Add an "auto-safe" mode, mostly triggered by Ubuntu's nonsense to force
hwdec=vaapi in the global config file in their mpv package. But to be
honest it's probably something more people want.

This is implemented as explicit whitelist. On Windows, HEVC/Intel is
sometimes broken, but it's still whitelisted, and in theory we'd need a
detailed whitelist of device names etc. (like for example browsers tend
to do). On OSX, videotoolbox is a pretty bad choice, but unfortunately
the only one, so it's whitelisted too. There may be a larger number of
hwdec wrappers that work anyway, and I'm for example ignoring Android.

DOCS/man/options.rst

@@ -998,7 +998,10 @@ Video
 
         Always enabling HW decoding by putting it into the config file is
         discouraged. If you use the Ubuntu package, delete ``/etc/mpv/mpv.conf``,
-        as the package tries to enable HW decoding by default.
+        as the package tries to enable HW decoding by default by setting
+        ``hwdec=vaapi`` (which is less than ideal, and may even cause
+        sub-optimal wrappers to be used). Or at least change it to
+        ``hwdec=auto-safe``.
 
     Use one of the auto modes if you want to enable hardware decoding.
     Explicitly selecting the mode is mostly meant for testing and debugging.
@@ -1010,11 +1013,25 @@ Video
         Even if enabled, hardware decoding is still only white-listed for some
         codecs. See ``--hwdec-codecs`` to enable hardware decoding in more cases.
 
+    .. admonition:: Which method to choose?
+
+        - If you only want to enable hardware decoding at runtime, don't set the
+          parameter, or put ``hwdec=no`` into your ``mpv.conf`` (relevant on
+          distros which force-enable it by default, such as on Ubuntu). Use the
+          ``Ctrl+h`` default binding to enable it at runtime.
+        - If you're not sure, but want hardware decoding always enabled by
+          default, put ``hwdec=auto-safe`` into your ``mpv.conf``, and
+          acknowledge that this use case is not "really" supported and may cause
+          problems.
+        - If you want to test available hardware decoding methods, pass
+          ``--hwdec=auto --hwdec-codecs`` and look at the terminal output.
+
     ``<api>`` can be one of the following:
 
     :no:        always use software decoding (default)
-    :auto:      enable best hw decoder (see below)
+    :auto:      forcibly enable any hw decoder found (see below)
     :yes:       exactly the same as ``auto``
+    :auto-safe: enable any whitelisted hw decoder (see below)
     :auto-copy: enable best hw decoder with copy-back (see below)
     :vdpau:     requires ``--vo=gpu`` with X11, or ``--vo=vdpau`` (Linux only)
     :vdpau-copy: copies video back into system RAM (Linux with some GPUs only)
@@ -1048,6 +1065,20 @@ Video
     work, it will always fall back to software decoding, instead of trying the
     next method (might matter on some Linux systems).
 
+    ``auto-safe`` is similar to ``auto``, but allows only whitelisted methods
+    that are considered "safe". This is supposed to be a reasonable way to
+    enable hardware decdoding by default in a config file (even though you
+    shouldn't do that anyway; prefer runtime enabling with ``Ctrl+h``). Unlike
+    ``auto``, this will not try to enable unknown or known-to-be-bad methods. In
+    addition, this may disable hardware decoding in other situations when it's
+    known to cause problems, but currently this mechanism is quite primitive.
+    (As an example for something that still causes problems: certain
+    combinations of HEVC and Intel chips on Windows tend to cause mpv to crash,
+    most likely due to driver bugs.)
+
+    ``auto-copy-safe`` selects the union of methods selected with ``auto-safe``
+    and ``auto-copy``.
+
     ``auto-copy`` selects only modes that copy the video data back to system
     memory after decoding. This selects modes like ``vaapi-copy`` (and so on).
     If none of these work, hardware decoding is disabled. This mode is usually
@@ -1074,8 +1105,9 @@ Video
     output path. To use this deinterlacing you must pass the option:
     ``vd-lavc-o=deint=[weave|bob|adaptive]``.
     Pass ``weave`` (or leave the option unset) to not attempt any
-    deinterlacing. ``cuda`` should always be preferred unless the ``gpu``
-    vo is not being used or filters are required.
+    deinterlacing. ``cuda`` should always be preferred over ``cuda-copy`` unless
+    the ``gpu`` vo is not being used or filters are required. Using ``nvdec``
+    should be preferred on Nvidia hardware.
 
     ``nvdec`` is a newer implementation of CUVID/CUDA decoding, which uses the
     FFmpeg decoders for file parsing. Experimental, is known not to correctly

video/decode/vd_lavc.c

@@ -155,6 +155,7 @@ struct hwdec_info {
     enum AVPixelFormat pix_fmt; // if not NONE, select in get_format
     bool use_hw_frames; // set AVCodecContext.hw_frames_ctx
     bool use_hw_device; // set AVCodecContext.hw_device_ctx
+    unsigned int flags; // HWDEC_FLAG_*
 
     // for internal sorting
     int auto_pos;
@@ -216,19 +217,33 @@ typedef struct lavc_ctx {
     struct mp_decoder public;
 } vd_ffmpeg_ctx;
 
+enum {
+    HWDEC_FLAG_AUTO         = (1 << 0), // prioritize in autoprobe order
+    HWDEC_FLAG_WHITELIST    = (1 << 1), // whitelist for auto-safe
+};
+
+struct autoprobe_info {
+    const char *method_name;
+    unsigned int flags;         // HWDEC_FLAG_*
+};
+
 // Things not included in this list will be tried last, in random order.
-static const char *const hwdec_autoprobe_order[] = {
-    "d3d11va",
-    "dxva2",
-    "dxva2-copy",
-    "d3d11va-copy",
-    "nvdec",
-    "nvdec-copy",
-    "vaapi",
-    "vaapi-copy",
-    "vdpau",
-    "vdpau-copy",
-    0
+const struct autoprobe_info hwdec_autoprobe_info[] = {
+    {"d3d11va",         HWDEC_FLAG_AUTO | HWDEC_FLAG_WHITELIST},
+    {"dxva2",           HWDEC_FLAG_AUTO},
+    {"dxva2-copy",      HWDEC_FLAG_AUTO | HWDEC_FLAG_WHITELIST},
+    {"d3d11va-copy",    HWDEC_FLAG_AUTO | HWDEC_FLAG_WHITELIST},
+    {"nvdec",           HWDEC_FLAG_AUTO | HWDEC_FLAG_WHITELIST},
+    {"nvdec-copy",      HWDEC_FLAG_AUTO | HWDEC_FLAG_WHITELIST},
+    {"vaapi",           HWDEC_FLAG_AUTO | HWDEC_FLAG_WHITELIST},
+    {"vaapi-copy",      HWDEC_FLAG_AUTO | HWDEC_FLAG_WHITELIST},
+    {"vdpau",           HWDEC_FLAG_AUTO},
+    {"vdpau-copy",      HWDEC_FLAG_AUTO | HWDEC_FLAG_WHITELIST},
+    {"mmal",            HWDEC_FLAG_AUTO},
+    {"mmal-copy",       HWDEC_FLAG_AUTO | HWDEC_FLAG_WHITELIST},
+    {"videotoolbox",    HWDEC_FLAG_AUTO | HWDEC_FLAG_WHITELIST},
+    {"videotoolbox-copy", HWDEC_FLAG_AUTO | HWDEC_FLAG_WHITELIST},
+    {0}
 };
 
 static int hwdec_compare(const void *p1, const void *p2)
@@ -266,9 +281,14 @@ static void add_hwdec_item(struct hwdec_info **infos, int *num_infos,
 
     info.rank = *num_infos;
     info.auto_pos = INT_MAX;
-    for (int x = 0; hwdec_autoprobe_order[x]; x++) {
-        if (strcmp(hwdec_autoprobe_order[x], info.method_name) == 0)
-            info.auto_pos = x;
+
+    for (int x = 0; hwdec_autoprobe_info[x].method_name; x++) {
+        const struct autoprobe_info *entry = &hwdec_autoprobe_info[x];
+        if (strcmp(entry->method_name, info.method_name) == 0) {
+            info.flags |= entry->flags;
+            if (info.flags & HWDEC_FLAG_AUTO)
+                info.auto_pos = x;
+        }
     }
 
     MP_TARRAY_APPEND(NULL, *infos, *num_infos, info);
@@ -434,8 +454,11 @@ static void select_and_set_hwdec(struct mp_filter *vd)
     bool hwdec_auto_all = bstr_equals0(opt, "auto") ||
                           bstr_equals0(opt, "yes") ||
                           bstr_equals0(opt, "");
-    bool hwdec_auto_copy = bstr_equals0(opt, "auto-copy");
-    bool hwdec_auto = hwdec_auto_all || hwdec_auto_copy;
+    bool hwdec_auto_safe = bstr_equals0(opt, "auto-safe") ||
+                           bstr_equals0(opt, "auto-copy-safe");
+    bool hwdec_auto_copy = bstr_equals0(opt, "auto-copy") ||
+                           bstr_equals0(opt, "auto-copy-safe");
+    bool hwdec_auto = hwdec_auto_all || hwdec_auto_copy || hwdec_auto_safe;
 
     if (!hwdec_requested) {
         MP_VERBOSE(vd, "No hardware decoding requested.\n");
@@ -460,6 +483,9 @@ static void select_and_set_hwdec(struct mp_filter *vd)
                                  bstr_equals0(opt, hwdec->name)))
                 continue;
 
+            if (hwdec_auto_safe && !(hwdec->flags & HWDEC_FLAG_WHITELIST))
+                continue;
+
             MP_VERBOSE(vd, "Looking at hwdec %s...\n", hwdec->name);
 
             if (hwdec_auto_copy && !hwdec->copying) {
@@ -530,6 +556,12 @@ static int hwdec_validate_opt(struct mp_log *log, const m_option_t *opt,
 
         talloc_free(hwdecs);
 
+        mp_info(log, "  auto (yes '')\n");
+        mp_info(log, "  no\n");
+        mp_info(log, "  auto-safe\n");
+        mp_info(log, "  auto-copy\n");
+        mp_info(log, "  auto-copy-safe\n");
+
         return M_OPT_EXIT;
     }
     return 0;