📝 Updated application.yml and added README.md for vvd-extractor

Improved the comments in the application.yml file for a clearer understanding of each configuration field, making it easy to configure the application for new users.
A README.md file was added to provide detailed information for the Extractor module: its functionalities, prerequisites, and instructions for setting up and running the module. The README also gives an explicit description of the configurations in the application.yml file. This update enhances comprehension and user experience.

Author: CXwudi

vvd-extractor/README.md

@@ -0,0 +1,78 @@
+# Extractor
+
+This module, as the final module, mainly takes charge of two things:
+
+1. Extracting and wrapping the audio source from
+   the downloaded media source from the previous module (`vvd-downloader`).
+2. Filling the metadata and embedding the thumbnail of the extracted audio file
+   with the song information from the `-songInfo` JSON file
+
+The output of this module is only a directory of audio files with metadata and thumbnail embedded.
+
+## Before moving on
+
+If you haven't read the common document yet, please read it first: [Common document](../doc/common%20part.md)
+
+## Additional Prerequisites
+
+Besides the common prerequisites, you also need:
+
+1. Python3 (This module relies on some python codes to perform metadata manipulation)
+2. `pip install mutagen` (Run this command to install the mutagen library)
+3. FFmpeg (Highly recommended the [yt-dlp's distribution](https://github.com/yt-dlp/FFmpeg-Builds/releases/tag/latest))
+4. [MediaInfo CLI](https://mediaarea.net/en/MediaInfo/Download)
+
+## All configurations
+
+All configurations can be found in [`application.yml`](./src/main/resources/application.yml) file.
+
+Below is a copy of the content of the `application.yml` file for your reference. However, make sure to check for any updates to
+the file yourself:
+
+```yaml
+io: # all fields are required
+  # this must be pointing to the output directory of the previous module, the task producer module. In another word, the directory specified in the 'io.output-directory' field of the previous module
+  # can be an absolute path or a relative path from the application current running directory
+  input-directory:
+  # the output directory of this module, can be an absolute path or a relative path from the application current running directory
+  output-directory:
+  # the error directory of this module, used for reporting errors for debugging, can be an absolute path or a relative path from the application current running directory
+  error-directory:
+
+config: # configuration
+  # all fields are required
+  environment: 
+    # specify the launch CMD of each dependency as a list of string.
+    # All commands will be executed using the root directory of the project as the current directory
+    python-launch-cmd:
+    ffmpeg-launch-cmd:
+    mediainfo-launch-cmd:
+
+  # all fields are required
+  batch:
+    # number of files to process in parallel, default is 0 which represents # of cores
+    batch-size: 0 
+
+  # all fields are required
+  process:
+    # This two fields control the timeout of each process in this module
+    # Each process in this module should be run in fairly quick time, even a one-hour video should be run in less than 2 minutes
+    # if you think you need more time, change the setting here
+    timeout: 5
+    unit: minutes
+
+  # all fields are required
+  retry:
+    retry-on-extraction: 2 # number of times to retry on audio extraction error
+    retry-on-tagging: 2 # number of times to retry on audio file tagging error
+
+  # optional fields
+  current-time:
+    # The module will modify the last modified time of the audio file to match the order of input tasks.
+    # Specifically, a task with a smaller order number in the `-task` JSON file will have an earlier last modified time.
+    # But the module needs a base timestamp to calculate the last modified time of each audio file
+    # By default, this field is empty means using the time when this app is launched.
+    # If you want to start from a specific time, change the setting here
+    # The format is yyyy-MM-dd HH:mm:ss, with the local time zone in this running device
+    start-from: ""
+```

vvd-extractor/src/main/resources/application.yml

@@ -1,32 +1,47 @@
-
-io: # input, output, and error output dir, can be relative path from the terminal current directory
+io: # all fields are required
+  # this must be pointing to the output directory of the previous module, the task producer module. In another word, the directory specified in the 'io.output-directory' field of the previous module
+  # can be an absolute path or a relative path from the application current running directory
   input-directory:
+  # the output directory of this module, can be an absolute path or a relative path from the application current running directory
   output-directory:
+  # the error directory of this module, used for reporting errors for debugging, can be an absolute path or a relative path from the application current running directory
   error-directory:
 
 config: # configuration
-  environment: # all cmd are list of strings, executed with the root directory of the project as the current directory
+  # all fields are required
+  environment:
+    # specify the launch CMD of each dependency as a list of string.
+    # All commands will be executed using the root directory of the project as the current directory
     python-launch-cmd:
     ffmpeg-launch-cmd:
     mediainfo-launch-cmd:
 
+  # all fields are required
   batch:
-    batch-size: 0 # number of files to process in parallel, default is 0 which represents # of cores
+    # number of files to process in parallel, default is 0 which represents # of cores
+    batch-size: 0
 
+  # all fields are required
   process:
-    # each process in this module should be run in fairly quick time, even though for a one-hour video, it should be run in less than 5 minutes
+    # This two fields control the timeout of each process in this module
+    # Each process in this module should be run in fairly quick time, even a one-hour video should be run in less than 2 minutes
     # if you think you need more time, change the setting here
     timeout: 5
     unit: minutes
 
+  # all fields are required
   retry:
     retry-on-extraction: 2 # number of times to retry on audio extraction error
     retry-on-tagging: 2 # number of times to retry on audio file tagging error
 
+  # optional fields
   current-time:
-    # by default, this field is empty means using the time when this app is launched.
-    # if you want to start from a specific time, change the setting here
-    # the format is yyyy-MM-dd HH:mm:ss, with your local time zone
+    # The module will modify the last modified time of the audio file to match the order of input tasks.
+    # Specifically, a task with a smaller order number in the `-task` JSON file will have an earlier last modified time.
+    # But the module needs a base timestamp to calculate the last modified time of each audio file
+    # By default, this field is empty means using the time when this app is launched.
+    # If you want to start from a specific time, change the setting here
+    # The format is yyyy-MM-dd HH:mm:ss, with the local time zone in this running device
     start-from: ""