getting something out of buffer

gir:field to get stuff out of structs
but getting 'data still doesn't work null in length

gstreamer/capturing-frames.lisp

@@ -8,6 +8,7 @@
 (in-package :capturing-frames)
 (gir:require-namespace "GLib")
 (defvar *gstreamer* (gir:require-namespace "Gst"))
+(defvar *gstapp* (gir:require-namespace "GstApp"))
 
 (defun cast-with-videobox (&optional stream-num)
   (gir:invoke (*gstreamer* 'init) '())
@@ -20,7 +21,8 @@
 			(queue1 (gir:invoke (*gstreamer* "ElementFactory" 'make) "queue" "queue1"))
          (queue2 (gir:invoke (*gstreamer* "ElementFactory" 'make) "queue" "queue2"))
          (sink (gir:invoke (*gstreamer* "ElementFactory" 'make) "autovideosink" "sink"))
-			(appsink (gir:invoke (*gstreamer* "ElementFactory" 'make) "appsink" "appsink")))
+			(appsink (gir:invoke (*gstreamer* "ElementFactory" 'make) "appsink" "appsink"))
+			)
 	 (when stream-num
 		;; Set pipewiresrc properties, such as the path
 		(setf (gir:property source 'path) (format nil "~A" stream-num)))
@@ -49,29 +51,49 @@
 	 (gir:invoke (pipeline 'set-state) (gir:nget *gstreamer* "State" :playing))
 	 	 
     ;; Example: Move the video 10 pixels down and 20 pixels to the right
-	 pipeline))
+	 (values pipeline appsink)))
 
 (defun process-frame (sample)
+  (format t ">>> got to process sample with ~A~%" sample)
   (let* ((buffer (gir:invoke (sample 'get-buffer)))
-         (info (gir:invoke (buffer 'get-memory) 0))
+         (info (gir:invoke (sample 'get-info)))
-         (map-info (gir:invoke (info 'map) (gir:nget *gstreamer* "MapFlags" :read)))
+			(caps (gir:invoke (sample 'get-caps)))
-         (data (gir:property map-info 'data))
+			(caps-struct (gir:invoke (caps 'get-structure) 0))
-         (size (gir:property map-info 'size)))
+			(width (gir:invoke ((gir:invoke (caps-struct 'get-value) "width") 'get-int)))
-    ;; Process the frame data here
+			(height (gir:invoke ((gir:invoke (caps-struct 'get-value) "height") 'get-int))))
-    (format t "Received frame of size ~A bytes~%" size)
+	 (multiple-value-bind (found map-info) (gir:invoke (buffer 'map) (gir:nget *gstreamer* "MapFlags" :read))
-    ;; Example: Calculate average brightness
+		(format t ">>>> the buffer has offset ~A~%" (gir:field buffer 'offset))
-    (let ((sum 0))
+		(format t ">>>> what's in struct? ~A~%" (gir:invoke (caps-struct 'to-string)))
-      (dotimes (i size)
+		(format t ">>>> the fields are width ~A, height ~A~%" width height)
-        (incf sum (aref data i)))
+		(format t ">>>> and map result are ~A and ~A~%" found map-info)
-      (format t "Average brightness: ~A~%" (/ sum size)))
+		(when found
+		  (let ((data (gir:field map-info 'data))
+				  (size (gir:field map-info 'size)))
+			 (format t ">>>> and struct info? ~A~%" map-info)
+;			 (format t ">>>> and data has size ~A and buf ~A~%" size (or data "empty data"))
+			 )))
 	 ;; Unmap the memory when done
-    (gir:invoke (info 'unmap) map-info)))
+    ;; (gir:invoke (info 'unmap) map-info)
+	 ))
 
 (defun start-processing (appsink)
   (gir:connect appsink "new-sample"
                (lambda (appsink)
+					  (format t ">> got printed object ~A~%" appsink)
+					  (format t ">> got printed class ~A~%" (gir:gir-class-of appsink))
+					  (format t ">> trying to get method on sink ~A~%" (gir:nget appsink 'pull-sample))
 					  (let ((sample (gir:invoke (appsink 'pull-sample))))
                    (when sample
-                     (process-frame sample)
+                     (process-frame sample)))
-                     (gir:invoke (sample 'unref))))
+
+					  
                  (gir:nget *gstreamer* "FlowReturn" :ok))))
+
+(defun try-run ()
+  (multiple-value-bind (pipeline appsink) (cast-with-videobox)
+	 (format t "got appsink ~A" appsink)
+	 (start-processing appsink)
+	 (loop
+		(sleep 1))))
+
+;(try-run)

notes.org

@@ -304,3 +304,85 @@ last time i got stuck on video displaying frozen when i tried to add appsink
 
 just re-checking my basic gstreamer pipeline and screencast start - thing works
 but i want to clean it up i guess, to allow for simpler retries?
+** so, for the appsnk there are signals
+https://gstreamer.freedesktop.org/documentation/app/appsink.html?gi-language=python#appsink::new-sample
+
+ new-sample
+
+#+begin_src python
+def new_sample_callback (appsink, udata):
+    #python callback for the 'new-sample' signal
+#+end_src
+
+Signal that a new sample is available.
+
+but how do i connect to a callback from common lisp and gobject introspection
+https://github.com/andy128k/cl-gobject-introspection
+does the gitlab repo has info on callbacks?
+
+can't seem to call method 'pull-sample'
+maybe article will help?
+https://gstreamer.freedesktop.org/documentation/application-development/advanced/pipeline-manipulation.html?gi-language=python#grabbing-data-with-appsink
+
+well, this looks like method on gst namespace? "gst_app_sink_pull_sample()"
+https://gstreamer.freedesktop.org/documentation/applib/gstappsink.html?gi-language=python#gst_app_sink_pull_sample
+
+there's article for python bindings
+https://lifestyletransfer.com/how-to-use-gstreamer-appsink-in-python/
+* [2024-08-22 Thu]
+** hey, i think this is progress
+i am able to call appsink 'pull-sample after all (for some reason, i don't know what i was doing differently)
+
+new error:
+>>> got to process sample with #<STRUCT-INSTANCE {10128D02F3}>
+but in the code for processing of the sample some type errors
+
+Backtrace:
+ 0: ((:METHOD GIR::THIS-OF (T)) T) [fast-method]
+ 1: (GIR:PROPERTY T DATA)
+ 2: (PROCESS-FRAME #<GIR::STRUCT-INSTANCE {100BCDAB73}>)
+ 3: ((LAMBDA (APPSINK) :IN START-PROCESSING) #<GIR::OBJECT-INSTANCE {100BBE02D3}>)
+
+ok, but when i have struct instance, how do i introspect it?
+** let's just go and read documentation for the type that's returned from pull-sample, sure
+also there's that python code, right?
+doc 1: get sample on appsink https://people.freedesktop.org/~tsaunier/documentation/gst-plugins-base-app-1.0/gstappsink.html?gi-language=c#gst_app_sink_pull_sample
+doc 2: GstSample class https://people.freedesktop.org/~tsaunier/documentation/gstreamer-1.0/gstsample.html?gi-language=c#GstSample
+
+so on GstSample everything is taken as results of funciton calls? let's try that
+
+well, maybe i don't need get-info on sample, it returns null, maybe i need it on buffer?
+doc 3: get-buffer on sample  https://people.freedesktop.org/~tsaunier/documentation/gstreamer-1.0/gstsample.html?gi-language=python#gst_sample_get_buffer
+doc 4: buffer class info https://people.freedesktop.org/~tsaunier/documentation/gstreamer-1.0/gstbuffer.html?gi-language=python#gst_buffer_peek_memory
+
+** i'm recommended to look into GstBuffer.map
+https://people.freedesktop.org/~tsaunier/documentation/gstreamer-1.0/gstbuffer.html?gi-language=python#gst_buffer_map
+
+it returns some https://people.freedesktop.org/~tsaunier/documentation/gstreamer-1.0/gstmemory.html?gi-language=python#GstMapInfo
+
+** struggling, searching for answers
+https://github.com/andy128k/cl-gobject-introspection/issues/73#issuecomment-755316735
+Examples of inspection of a repository can be found in test files.
+
+https://github.com/andy128k/cl-gobject-introspection/blob/master/test/test1.lisp
+
+and i mean it's possible that referencing members of a structure is not implemented?
+
+so, huh
+using internal functions
+#+begin_src lisp
+(data (gir:fields-dict-of (gir:struct-class-of map-info)))  
+#+end_src
+i see
+>>>> and data has size NIL and buf ((memory . #<FIELD-INFO {100FEB4083}>)
+                                    (flags . #<FIELD-INFO {100FEB4153}>)
+                                    (data . #<FIELD-INFO {100FEB4223}>)
+                                    (size . #<FIELD-INFO {100FEB42F3}>)
+                                    (maxsize . #<FIELD-INFO {100FEB43C3}>)
+                                    (user_data . #<FIELD-INFO {100FEB4493}>)
+                                    (_gst_reserved
+                                     . #<FIELD-INFO {100FEB4563}>))
+; Evaluation aborted on T
+CAPTURING-FRAMES>
+
+so. there are data and size fields.