From 02c931780e08bd21bc6b48136a5430a405478047 Mon Sep 17 00:00:00 2001
From: Théo de la Hogue
Date: Thu, 1 Feb 2024 02:04:36 +0100
Subject: Adding VideoWriter class. Using it in demo. Documenting its use.

---
 docs/user_guide/gaze_analysis_pipeline/logging.md | 31 ++++++++++++++++++++---
 1 file changed, 27 insertions(+), 4 deletions(-)

(limited to 'docs/user_guide/gaze_analysis_pipeline/logging.md')

diff --git a/docs/user_guide/gaze_analysis_pipeline/logging.md b/docs/user_guide/gaze_analysis_pipeline/logging.md
index 617690f..8afb511 100644
--- a/docs/user_guide/gaze_analysis_pipeline/logging.md
+++ b/docs/user_guide/gaze_analysis_pipeline/logging.md
@@ -3,7 +3,7 @@ Log gaze analysis
 
 [ArFrame](../../argaze.md/#argaze.ArFeatures.ArFrame) and [ArLayer](../../argaze.md/#argaze.ArFeatures.ArLayer) analysis can be logged by registering observers to their **look** method.
 
-## Enable ArFrame and ArLayer analysis logging
+## Export gaze analysis to CSV file
 
 [ArFrame](../../argaze.md/#argaze.ArFeatures.ArFrame) and [ArLayer](../../argaze.md/#argaze.ArFeatures.ArLayer) have an observers attribute to enable pipeline execution logging.
 
@@ -36,7 +36,7 @@ from argaze.utils import UtilsFeatures
 class ScanPathAnalysisLogger(DataFeatures.PipelineStepObserver, UtilsFeatures.FileWriter):
 
     def on_look(self, timestamp, ar_frame):
-        """Log scan path metrics"""
+        """Log scan path metrics.ar_frame"""
 
         if ar_frame.analysis_available:
 
@@ -76,7 +76,7 @@ from argaze.utils import UtilsFeatures
 class AOIScanPathAnalysisLogger(DataFeatures.PipelineStepObserver, UtilsFeatures.FileWriter):
 
     def on_look(self, timestamp, ar_layer):
-        """Log aoi scan path metrics"""
+        """Log aoi scan path metrics."""
 
         if ar_layer.analysis_available:
 
@@ -104,4 +104,27 @@ Assuming that [ArGaze.GazeAnalysis.NGram](../../argaze.md/#argaze.GazeAnalysis.N
 
 !!! note ""
 
-    Learn to [script the pipeline](./advanced_topics/scripting.md) to know more about [ArFrame](../../argaze.md/#argaze.ArFeatures.ArFrame) and [ArLayers](../../argaze.md/#argaze.ArFeatures.ArLayer) attributes.
\ No newline at end of file
+    Learn to [script the pipeline](./advanced_topics/scripting.md) to know more about [ArFrame](../../argaze.md/#argaze.ArFeatures.ArFrame) and [ArLayers](../../argaze.md/#argaze.ArFeatures.ArLayer) attributes.
+
+### Export gaze analysis to video file
+
+As explained in [pipeline steps visualisation chapter](visualisation.md), it is possible to get [ArFrame.image](../../argaze.md/#argaze.ArFeatures.ArFrame.image) once timestamped gaze positions have been processed by [ArFrame.look](../../argaze.md/#argaze.ArFeatures.ArFrame.look) method.
+
+```python
+from argaze import DataFeatures
+from argaze.utils import UtilsFeatures
+
+class VideoRecorder(DataFeatures.PipelineStepObserver, UtilsFeatures.VideoWriter):
+
+        def on_look(self, timestamp, ar_frame):
+            """Record frame image into video file."""
+
+            self.write(ar_frame.image())
+
+# Export recorder as observer
+__observers__ = {
+    "Video recorder": VideoRecorder(path="./video.mp4", width=1920, height=1080, fps=15)
+    }
+```
+
+Assuming that [ArFrame.image_parameters](../../argaze.md/#argaze.ArFeatures.ArFrame.image_parameters) are provided, ***video.mp4*** file would be created.
\ No newline at end of file
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