update readme with description, quickstart, contribution details

Author: rioam2

README.md

@@ -1,2 +1,144 @@
 # aftereffects-aep-parser
-An unofficial parser for Adobe After Effects *.aep project files
+
+This project is dedicated to reverse-engineering, parsing and exposing useful APIs for understanding Adobe After Effects AEP project files. This may be useful for a variety of reasons. For example, one might want to programmatically determine the number of compositions in a project, their resolution(s), framerate, etc. Traditionally, one would need to piggyback the ExtendScript engine running within After Effects to retrieve this information. While this procedure is fairly easy to accomplish, it is exponentially more resource expensive than static file analysis, and requires a running instance of the After Effects Scripting Engine (which can only be run on Windows and MacOS). 
+
+# Quick Start
+
+```bash
+go get -u github.com/boltframe/aftereffects-aep-parser
+```
+
+```go
+package main
+
+import (
+  "fmt"
+  aep "github.com/boltframe/aftereffects-aep-parser"
+)
+
+func main() {
+  project, err := aep.Open("./my-project.aep")
+  if err != nil {
+    panic(err)
+  }
+  fmt.Println(project)
+}
+```
+
+# Contributing
+
+Any and all contributions are welcome! There is no official procedure for contributing yet, but please start by opening a new issue describing your findings and anticipated contribution. Thank you!
+
+# Research Procedure
+
+After Effects Project files are currently encoded using the Resource Interchange File Format (RIFF) in a Big-Endian byte-ordering (also known as RIFX). This can be confirmed by inspecting the first four bytes of any AEP file which will contain the following ASCII characters: `RIFX....`. Once parsed into [Chunks](https://en.wikipedia.org/wiki/Resource_Interchange_File_Format#Explanation), you can inspect the internal representation and *attempt* to understand its structure.
+
+I have found that the online tool [Kaitai](https://ide.kaitai.io) is extremely helpful for quickly viewing structured binary data. I use the following (possibly outdated) language definition for validating AEP files:
+
+```ksy
+meta:
+  id: aep
+  endian: be
+  file-extension: aep
+
+seq:
+  - id: magic1
+    contents: RIFX
+  - id: file_size
+    type: u4
+  - id: magic2
+    contents: Egg!
+  - id: data
+    type: blocks
+    size: file_size - 4
+    
+types:
+  blocks:
+    seq:
+      - id: entries
+        type: block
+        repeat: eos
+  block:
+    seq: 
+      - id: block_type
+        type: u4
+        enum: chunk_type
+      - id: block_size
+        type: u4
+      - id: data
+        size: block_size
+        type: 
+          switch-on: block_type
+          cases:
+            'chunk_type::list': list_body
+            'chunk_type::utf8': utf8_body
+            'chunk_type::cdta': cdta_body
+            'chunk_type::idta': idta_body
+            'chunk_type::cmta': utf8_body
+            'chunk_type::fdta': fdta_body
+            _: ascii_body
+      - id: padding
+        type: u1
+        if: (block_size % 2) != 0
+  list_body:
+    seq:
+      - id: identifier
+        type: str
+        encoding: ascii
+        size: 4
+      - id: entries
+        type: blocks
+  utf8_body:
+    seq:
+      - id: data
+        type: str
+        encoding: utf8
+        size-eos: true
+  ascii_body:
+    seq:
+      - id: data
+        type: str
+        encoding: ascii
+        size-eos: true
+  idta_body:
+    seq:
+      - id: unknown1
+        type: str
+        size: 18
+        encoding: ascii
+      - id: id
+        type: u2
+  fdta_body:
+    seq:
+      - id: unknown1
+        type: str
+        encoding: ascii
+        size: 1
+  cdta_body:
+    seq:
+      - id: unknown1
+        type: str
+        size: 140
+        encoding: ascii
+      - id: width
+        type: u2
+      - id: height
+        type: u2
+      - id: unknown2
+        type: str
+        size: 12
+        encoding: ascii
+      - id: frame_rate
+        type: u2
+        
+enums:
+  chunk_type:
+    0x4c495354: list
+    0x55746638: utf8
+    0x63647461: cdta # Composition data
+    0x69647461: idta # Item data
+    0x636d7461: cmta # Comment data
+    0x66647461: fdta # Folder data
+```
+
+By making small changes to an After Effects project and uploading it to the Kaitai viewer, you can narrow down on how data is represented, and start to write additional language definitions and structures.