gstplayer: feature parity with audioplayers player

- add audio balance setter/getter
- support releasing & prerolling a playback
  source
- add separate seeking info, duration and
  end of stream notifiers
- make gstreamer_video_player.h not
  depend on gstreamer headers (if possible)

Author: ardera

src/plugins/gstreamer_video_player.h

@@ -5,6 +5,8 @@
 #include "util/lock_ops.h"
 #include "util/refcounting.h"
 
+#include <gst/video/video-format.h>
+
 #include "config.h"
 
 #if !defined(HAVE_EGL_GLES2)
@@ -65,6 +67,19 @@ struct video_info;
 struct gstplayer;
 struct flutterpi;
 
+typedef struct _GstStructure GstStructure;
+
+/// Create a gstreamer video player.
+struct gstplayer *gstplayer_new(
+    struct flutterpi *flutterpi,
+    const char *uri,
+    void *userdata,
+    bool play_video,
+    bool play_audio,
+    bool subtitles,
+    GstStructure *headers
+);
+
 /// Create a gstreamer video player that loads the video from a flutter asset.
 ///     @arg asset_path     The path of the asset inside the asset bundle.
 ///     @arg package_name   The name of the package containing the asset
@@ -131,6 +146,11 @@ int gstplayer_pause(struct gstplayer *player);
 ///     @returns Current playback position, in milliseconds from the beginning of the video.
 int64_t gstplayer_get_position(struct gstplayer *player);
 
+/// Get the duration of the currently playing medium.
+///     @returns  Duration of the current medium in milliseconds, -1 if the duration
+///               is not yet known, or INT64_MAX for live sources.
+int64_t gstplayer_get_duration(struct gstplayer *player);
+
 /// Set whether the video should loop.
 ///     @arg looping    Whether the video should start playing from the beginning when the
 ///                     end is reached.
@@ -155,6 +175,14 @@ int gstplayer_step_forward(struct gstplayer *player);
 
 int gstplayer_step_backward(struct gstplayer *player);
 
+void gstplayer_set_audio_balance(struct gstplayer *player, float balance);
+
+float gstplayer_get_audio_balance(struct gstplayer *player);
+
+bool gstplayer_release(struct gstplayer *p);
+
+bool gstplayer_preroll(struct gstplayer *p, const char *uri);
+
 struct video_info {
     int width, height;
 
@@ -173,6 +201,17 @@ struct video_info {
 /// So you need to make sure you do the proper rethreading in the listener callback.
 struct notifier *gstplayer_get_video_info_notifier(struct gstplayer *player);
 
+struct seeking_info {
+    bool can_seek;
+    int64_t seek_begin_ms, seek_end_ms;
+};
+
+struct notifier *gstplayer_get_seeking_info_notifier(struct gstplayer *player);
+
+struct notifier *gstplayer_get_duration_notifier(struct gstplayer *player);
+
+struct notifier *gstplayer_get_eos_notifier(struct gstplayer *player);
+
 /// @brief Get the value notifier for the buffering state.
 ///
 /// Gets notified with a value of type `struct buffering_state*` when the buffering state changes.