ffmpeg: Remove the hw_device_ctx global

The ad-hoc libmfx setup code is the only place its still used, so move it
into that file.

fftools/ffmpeg.c

@@ -4759,7 +4759,6 @@ static int transcode(void)
         }
     }
 
-    av_buffer_unref(&hw_device_ctx);
     hw_device_free_all();
 
     /* finished ! */

fftools/ffmpeg.h

@@ -615,7 +615,6 @@ extern const AVIOInterruptCB int_cb;
 
 extern const OptionDef options[];
 extern const HWAccel hwaccels[];
-extern AVBufferRef *hw_device_ctx;
 #if CONFIG_QSV
 extern char *qsv_device;
 #endif

fftools/ffmpeg_opt.c

@@ -139,7 +139,6 @@ const HWAccel hwaccels[] = {
 #endif
     { 0 },
 };
-AVBufferRef *hw_device_ctx;
 HWDevice *filter_hw_device;
 
 char *vstats_filename;
@@ -536,21 +535,15 @@ static int opt_sdp_file(void *optctx, const char *opt, const char *arg)
 #if CONFIG_VAAPI
 static int opt_vaapi_device(void *optctx, const char *opt, const char *arg)
 {
-    HWDevice *dev;
     const char *prefix = "vaapi:";
     char *tmp;
     int err;
     tmp = av_asprintf("%s%s", prefix, arg);
     if (!tmp)
         return AVERROR(ENOMEM);
-    err = hw_device_init_from_string(tmp, &dev);
+    err = hw_device_init_from_string(tmp, NULL);
     av_free(tmp);
-    if (err < 0)
-        return err;
-    hw_device_ctx = av_buffer_ref(dev->device_ref);
-    if (!hw_device_ctx)
-        return AVERROR(ENOMEM);
-    return 0;
+    return err;
 }
 #endif
 

fftools/ffmpeg_qsv.c

@@ -28,6 +28,7 @@
 
 #include "ffmpeg.h"
 
+static AVBufferRef *hw_device_ctx;
 char *qsv_device = NULL;
 
 static int qsv_get_buffer(AVCodecContext *s, AVFrame *frame, int flags)