Real-time feature extraction from video stream data for stream ...

ai.cs.uni.dortmund.de

Real-time feature extraction from video stream data for stream ...

5. Data

plain text files in the .m3u(8) 1 -format, containing the locations of the actual media files.

Following the URL given in the watch channel response, we receive a .m3u-file, that

again refers to other .m3u-files. An example for such a response can be found in figure

5.5.

#EXTM3U

#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=64000

ZDF-live-64.m3u8?watchid= ...

#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=150000

ZDF-live-150.m3u8?watchid= ...

#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=300000

ZDF-live-300.m3u8?watchid= ...

#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=600000

ZDF-live-600.m3u8?watchid= ...

#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=1100000

ZDF-live-1100.m3u8?watchid= ...

Figure 5.5.: The .m3u-file received, when following the link given in the watch channel

response. This file routes the user to the correct playlist file, optimized for his

bandwidth.

Each given .m3u-entry in this file is again a playlist file, which is optimized for different

bandwidths. Hence users with faster internet connections get directed to a playlist

containing media elements with higher quality. After choosing the playlist, which is

appropriate for the available bandwidth, the right .m3u-file can be downloaded using

another GET-Request. This received playlist file now is a media playlist according to

the HTTP Live Streaming (HLS) Protocol [Pantos and May, 2009]. An example can be

found in figure 5.6.

#EXTM3U

#EXT-X-TARGETDURATION:4

#EXT-X-MEDIA-SEQUENCE:67978019

#EXT-X-KEY:METHOD=AES-128,URI="http://HOST/ZDF/live/64/6421.key?watc ..."

#EXTINF:4,

http://HOST/ZDF/live/64/67978019s.ts?__gda__= ...

#EXTINF:4,

http://HOST/ZDF/live/64/67978020s.ts?__gda__= ...

#EXTINF:4,

http://HOST/ZDF/live/64/67978021s.ts?__gda__= ...

#EXTINF:4,

http://HOST/ZDF/live/64/67978022s.ts?__gda__= ...

#EXTINF:4,

http://HOST/ZDF/live/64/67978023s.ts?__gda__= ...

Figure 5.6.: The .m3u-file received, when following one of the links given in the first

.m3u-file. This file contains references to the media segments.

This .m3u-playlist refers to a set of media segments, encoded in the MPEG-2 Transport

Stream (TS)-format. All media segments can be downloaded from the Zattoo server

and each of the segments contains four seconds of video and audio data. When putted

1 .m3u-files are usually encoded with the Latin-1 charset. The file ending 8 indicates that this file is the

unicode version of .m3u, which uses UTF-8 unicode characters

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