vaapi: always create AVHWDeviceContext on init

For convenience. Since we still have code that works even if creating a
AVHWDeviceContext fails, failure is ignored. (Although currently, it
succeeds creation even with the stale/abandoned vdpau wrapper driver.)

video/decode/vaapi.c

@@ -41,7 +41,6 @@ struct priv {
     struct mp_vaapi_ctx *ctx;
     bool own_ctx;
 
-    AVBufferRef *device_ref;
     AVBufferRef *frames_ref;
 };
 
@@ -72,7 +71,7 @@ static int init_decoder(struct lavc_ctx *ctx, int w, int h)
     }
 
     if (!p->frames_ref) {
-        p->frames_ref = av_hwframe_ctx_alloc(p->device_ref);
+        p->frames_ref = av_hwframe_ctx_alloc(p->ctx->av_device_ref);
         if (!p->frames_ref)
             return -1;
 
@@ -114,7 +113,6 @@ static void uninit(struct lavc_ctx *ctx)
         return;
 
     av_buffer_unref(&p->frames_ref);
-    av_buffer_unref(&p->device_ref);
 
     if (p->own_ctx)
         va_destroy(p->ctx);
@@ -143,16 +141,7 @@ static int init(struct lavc_ctx *ctx, bool direct)
 
     ctx->hwdec_priv = p;
 
-    p->device_ref = av_hwdevice_ctx_alloc(AV_HWDEVICE_TYPE_VAAPI);
-    if (!p->device_ref)
-        return -1;
-
-    AVHWDeviceContext *hwctx = (void *)p->device_ref->data;
-    AVVAAPIDeviceContext *vactx = hwctx->hwctx;
-
-    vactx->display = p->ctx->display;
-
-    if (av_hwdevice_ctx_init(p->device_ref) < 0)
+    if (!p->ctx->av_device_ref)
         return -1;
 
     return 0;

video/vaapi.c

@@ -151,6 +151,21 @@ static void va_info_callback(const char *msg)
     va_message_callback(msg, MSGL_V);
 }
 
+static void open_lavu_vaapi_device(struct mp_vaapi_ctx *ctx)
+{
+    ctx->av_device_ref = av_hwdevice_ctx_alloc(AV_HWDEVICE_TYPE_VAAPI);
+    if (!ctx->av_device_ref)
+        return;
+
+    AVHWDeviceContext *hwctx = (void *)ctx->av_device_ref->data;
+    AVVAAPIDeviceContext *vactx = hwctx->hwctx;
+
+    vactx->display = ctx->display;
+
+    if (av_hwdevice_ctx_init(ctx->av_device_ref) < 0)
+        av_buffer_unref(&ctx->av_device_ref);
+}
+
 struct mp_vaapi_ctx *va_initialize(VADisplay *display, struct mp_log *plog,
                                    bool probing)
 {
@@ -189,6 +204,11 @@ struct mp_vaapi_ctx *va_initialize(VADisplay *display, struct mp_log *plog,
     va_get_formats(res);
     if (!res->image_formats)
         goto error;
+
+    // For now, some code will still work even if libavutil fails on old crap
+    // libva drivers (such as the vdpau wraper). So don't error out on failure.
+    open_lavu_vaapi_device(res);
+
     return res;
 
 error:

video/vaapi.h

@@ -33,6 +33,7 @@ struct mp_vaapi_ctx {
     struct mp_hwdec_ctx hwctx;
     struct mp_log *log;
     VADisplay display;
+    struct AVBufferRef *av_device_ref; // AVVAAPIDeviceContext*
     struct va_image_formats *image_formats;
     bool gpu_memcpy_message;
     pthread_mutex_t lock;