Module Logic - Grade-A-Software/Comcast-DASH-VLC GitHub Wiki

Logic for parsing and playback

The DASH module utilizes a procedure to parse the contents of a DASH Manifest, download a timeline of short video files, and provide the stream of continuous video playback to the user.

1. Fetch DASH manifest.

• The DASH Manifest is stored on a server, typically with the filename "manifest.mpd"
• VLC accepts the URL of the manifest as a command line parameter.
  • ./vlc http://url.com/path/to/manifest.mpd
• From the GUI (for best performance):
  • File -> Open Network Stream (command-N on Mac / control-N on Linux)
    • Enter the URL.

2. Parse DASH manifest.

• The XML in the DASH Manifest follows a specific format.
  • This format is known as MPD, or Media Presentation Description.

3. Interpret manifest to formulate video URLs.

• The MPD format specifies a number of components. See: MPD Components and MPD parsing README
• These components allow the module to form a timeline of URLs corresponding to media MPEG-2 Transport Stream (.ts) files.

4. Fetch content in the video URL timeline.

• The existing DASH module has several components that facilitate this process
  • HTTP
  • XML
  • Buffer
• These components interact through the module.

5. Feed the content to VLC decoder.

• The VLC decoder relies on a block of bytes from which it can read, peek, and seek through media data.
• The DASH Module, DASH Manager and DASH Downloader facilitate this process.