* filesize_approx An estimate for the number of bytes
* player_url SWF Player URL (used for rtmpdump).
* protocol The protocol that will be used for the actual
- download, lower-case.
- "http", "https", "rtsp", "rtmp", "rtmp_ffmpeg", "rtmpe",
- "m3u8", "m3u8_native" or "http_dash_segments".
+ download, lower-case. One of "http", "https" or
+ one of the protocols defined in downloader.PROTOCOL_MAP
* fragment_base_url
Base URL for fragments. Each fragment's path
value (if present) will be relative to
fragment_base_url
* "duration" (optional, int or float)
* "filesize" (optional, int)
+ * is_from_start Is a live format that can be downloaded
+ from the start. Boolean
* preference Order number of this format. If this field is
present and not None, the formats get sorted
by this field, regardless of all other values.