upload
  The APPEND command is used to upload a chunk (consecutive byte range) of the media file. For example, a 3 MB file could be split into 3 chunks of size 1 MB, and uploaded using 3 APPEND command requests. After the entire file is uploaded, the next step is to call the FINALIZE command. There are a number of advantages of uploading a media file in small chunks:
- Improved reliability and success rates under low bandwidth network conditions 
- Uploads can be paused and resumed 
- File chunks can be retried individually 
- Ability to tune chunk sizes to match changing network conditions e.g on cellular clients 
Receiver
Media endpoint instance.
Return
Parameters
The media_id returned from the INIT command.
An ordered index of file chunk. It must be between 0-999 inclusive. The first segment has index 0, second segment has index 1, and so on.
Optional. Custom parameters of this request.