updating chapters activities

chapters.md

@@ -10,8 +10,6 @@ ffmpeg -f lavfi -i "smptebars=s=720x480:r=25:d=5" -f lavfi -i "aevalsrc=0.1*sin(
 
 This file will be used throughout the Chapters exercise.
 
-## MKXToolNix CLI
-
 ## MKXToolNix GUI
 
 ### Creating Chapters in Fixed Intervals 
@@ -111,6 +109,58 @@ Drop **chapters_test_pbcore.mkv** into MKVToolNix, and you should see the PBCore
 
 ### Exporting Attachments
 
+There isn't a way  to export attachments using the MKVToolNix GUI, so we'll save this for the CLI Portion!
+
+## MKXToolNix CLI
+
+### mkvpropedit
+
+mkvpropedit can be used to change the properties of an MKV file without having to rewrite the file entirely. The standard template for an mkvpropedit command looks something like this
+
+```
+mkvpropedit [input_file.mkv] --edit track:[target_track] --set [target_element]=[new_value]
+```
+
+To use this template, you'll need to replace everything in square brakets with your own values:
+
+`[input_file.mkv]` = the path to the files you wish edit
+`[target_track] ` = the track you wish to edit. This could be a video track, audio track, subtitle track, etc. 
+`[target_element]` = the element you wish to edit
+`[new_value]` = the new value for the element that you're updating. 
+
+The syntax for `[target_track] ` is "v1" for "first video track". "a1" for "first audio track, "a2" for second audio track, etc...
+
+The syntax for `[target_element]`, and `[new_value]` can be seen by typing `mkvpropedit -l`
+
+### Change Aspect Ratio
+
+The following command will change the aspect ratio of a the chapters_test.mkv to 16:9
+
+```
+mkvpropedit chapters_test.mkv --edit track:v1 --set display-width=16 --set display-height=9 --set display-unit=3
+```
+
+After running the command, open chapters_test.mkv. You should be able to immediately see the video display as 16:9 now. 
+
+You can also run mediainfo on the file, and see that it reports as 16:9
+
+```
+mediainfo chapters_test.mkv
+```
+
+To set the aspect ratio back to 4:3 use the following command
+
+```
+mkvpropedit chapters_test.mkv --edit track:v1 --set display-width=4 --set display-height=3 --set display-unit=3
+```
+
+
+update title
+
+language tags
+
+### Exporting Attachments
+
 The MKVToolNix GUI is not capable of exporting attachments, so you'll have to do it with some CLI apps. 
 
 First, we need to find out the ID of the attachment is. In order to do this type the following command:
@@ -157,3 +207,4 @@ Open up both PBCore files and compare!
 
 
 
+