lavd: add avdevice_dev_to_app_control_message API

New API allows to send messages from devices to application.
Signed-off-by: Lukasz Marek <lukasz.m.luki@gmail.com>

libavdevice/avdevice.c

@@ -44,3 +44,11 @@ int avdevice_app_to_dev_control_message(struct AVFormatContext *s, enum AVAppToD
         return AVERROR(ENOSYS);
     return s->oformat->control_message(s, type, data, data_size);
 }
+
+int avdevice_dev_to_app_control_message(struct AVFormatContext *s, enum AVDevToAppMessageType type,
+                                        void *data, size_t data_size)
+{
+    if (!s->control_message_cb)
+        return AVERROR(ENOSYS);
+    return s->control_message_cb(s, type, data, data_size);
+}

libavdevice/avdevice.h

@@ -104,6 +104,60 @@ enum AVAppToDevMessageType {
     AV_APP_TO_DEV_WINDOW_REPAINT = MKBETAG('R','E','P','A')
 };
 
+/**
+ * Message types used by avdevice_dev_to_app_control_message().
+ */
+enum AVDevToAppMessageType {
+    /**
+     * Dummy message.
+     */
+    AV_DEV_TO_APP_NONE = MKBETAG('N','O','N','E'),
+
+    /**
+     * Create window buffer message.
+     *
+     * Device requests to create a window buffer. Exact meaning is device-
+     * and application-dependent. Message is sent before rendering first
+     * frame and all one-shot initializations should be done here.
+     *
+     * data: NULL.
+     */
+    AV_DEV_TO_APP_CREATE_WINDOW_BUFFER = MKBETAG('B','C','R','E'),
+
+    /**
+     * Prepare window buffer message.
+     *
+     * Device requests to prepare a window buffer for rendering.
+     * Exact meaning is device- and application-dependent.
+     * Message is sent before rendering of each frame.
+     *
+     * data: NULL.
+     */
+    AV_DEV_TO_APP_PREPARE_WINDOW_BUFFER = MKBETAG('B','P','R','E'),
+
+    /**
+     * Display window buffer message.
+     *
+     * Device requests to display a window buffer.
+     * Message is sent when new frame is ready to be displyed.
+     * Usually buffers need to be swapped in handler of this message.
+     *
+     * data: NULL.
+     */
+    AV_DEV_TO_APP_DISPLAY_WINDOW_BUFFER = MKBETAG('B','D','I','S'),
+
+    /**
+     * Destroy window buffer message.
+     *
+     * Device requests to destroy a window buffer.
+     * Message is sent when device is about to be destroyed and window
+     * buffer is not required anymore.
+     *
+     * data: NULL.
+     */
+    AV_DEV_TO_APP_DESTROY_WINDOW_BUFFER = MKBETAG('B','D','E','S')
+};
+
 /**
  * Send control message from application to device.
  *
@@ -118,4 +172,18 @@ int avdevice_app_to_dev_control_message(struct AVFormatContext *s,
                                         enum AVAppToDevMessageType type,
                                         void *data, size_t data_size);
 
+/**
+ * Send control message from device to application.
+ *
+ * @param s         device context.
+ * @param type      message type.
+ * @param data      message data. Can be NULL.
+ * @param data_size size of message data.
+ * @return >= 0 on success, negative on error.
+ *         AVERROR(ENOSYS) when application doesn't implement handler of the message.
+ */
+int avdevice_dev_to_app_control_message(struct AVFormatContext *s,
+                                        enum AVDevToAppMessageType type,
+                                        void *data, size_t data_size);
+
 #endif /* AVDEVICE_AVDEVICE_H */

libavdevice/version.h

@@ -28,7 +28,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVDEVICE_VERSION_MAJOR  55
-#define LIBAVDEVICE_VERSION_MINOR   6
+#define LIBAVDEVICE_VERSION_MINOR   7
 #define LIBAVDEVICE_VERSION_MICRO 100
 
 #define LIBAVDEVICE_VERSION_INT AV_VERSION_INT(LIBAVDEVICE_VERSION_MAJOR, \

libavformat/avformat.h

@@ -952,6 +952,13 @@ typedef struct AVChapter {
 } AVChapter;
 
 
+/**
+ * Callback used by devices to communicate with application.
+ */
+typedef int (*av_format_control_message)(struct AVFormatContext *s, int type,
+                                         void *data, size_t data_size);
+
+
 /**
  * The duration of a video can be estimated through various ways, and this enum can be used
  * to know how the duration was estimated.
@@ -1360,6 +1367,19 @@ typedef struct AVFormatContext {
      * Muxing: Set by user via av_format_set_metadata_header_padding.
      */
     int metadata_header_padding;
+
+    /**
+     * User data.
+     * This is a place for some private data of the user.
+     * Mostly usable with control_message_cb or any future callbacks in device's context.
+     */
+    void *opaque;
+
+    /**
+     * Callback used by devices to communicate with application.
+     */
+    av_format_control_message control_message_cb;
+
 } AVFormatContext;
 
 int av_format_get_probe_score(const AVFormatContext *s);
@@ -1371,6 +1391,10 @@ AVCodec * av_format_get_subtitle_codec(const AVFormatContext *s);
 void      av_format_set_subtitle_codec(AVFormatContext *s, AVCodec *c);
 int       av_format_get_metadata_header_padding(const AVFormatContext *s);
 void      av_format_set_metadata_header_padding(AVFormatContext *s, int c);
+void *    av_format_get_opaque(const AVFormatContext *s);
+void      av_format_set_opaque(AVFormatContext *s, void *opaque);
+av_format_control_message av_format_get_control_message_cb(const AVFormatContext *s);
+void      av_format_set_control_message_cb(AVFormatContext *s, av_format_control_message callback);
 
 /**
  * Returns the method used to set ctx->duration.

libavformat/utils.c

@@ -107,6 +107,8 @@ MAKE_ACCESSORS(AVFormatContext, format, AVCodec *, video_codec)
 MAKE_ACCESSORS(AVFormatContext, format, AVCodec *, audio_codec)
 MAKE_ACCESSORS(AVFormatContext, format, AVCodec *, subtitle_codec)
 MAKE_ACCESSORS(AVFormatContext, format, int, metadata_header_padding)
+MAKE_ACCESSORS(AVFormatContext, format, void *, opaque)
+MAKE_ACCESSORS(AVFormatContext, format, av_format_control_message, control_message_cb)
 
 static AVCodec *find_decoder(AVFormatContext *s, AVStream *st, enum AVCodecID codec_id)
 {

libavformat/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFORMAT_VERSION_MAJOR 55
-#define LIBAVFORMAT_VERSION_MINOR 27
+#define LIBAVFORMAT_VERSION_MINOR 28
 #define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \