Live Streaming

Live video streaming came off pretty well, mostly thanks to the wonderful Ramon Navarro Bosch of the UPC and Gil Forçada's guifi.net crew.

If you reached this page wanting to know more information on how to stream a conference, the article So you want to stream a conference? sums up our experiences.

The Archives

The archives did not come out so well, due to configuration problems and an unexpected software bug. In many occasions, the video encoding took too much CPU, triggering a bug in the encoders that caused the streams to become out of sync. Additionally there were various sound problems. Click through for further details.

What we have is a set of raw video archives. By raw, that's to say that these are the videos recorded while we were doing live streaming. The aforementioned software problems made it difficult to cut the videos. For the most part, they have not been cut, so they can be quite large -- more than 2 gigabytes in one case.

Here are the files. There's an index.html there explaining what is available.

What to do with the videos

No correct player will play back these videos as they were intended to be played, because of the desynchronisation problems. Really sorry about this folks, I did not anticipate this and worked hard to fix it, but did not finish.

So the goal is to cut out individual talks, and have the audio and video in sync. Additionally it would be good if we could avoid re-encoding, because that leads to loss in quality, and the video was already only of the quality for streaming.

A first cut, to give you a smaller piece to work with, would be to chop the videos into pieces, which you can resynchronize later. The remuxer seems to work OK for this, although it does have some bugs.

At this point you will need to resynchronize the streams. One way would be to transcode to some other format, use a professional video editing tool to adjust the positions of the audio and video tracks, and then reencode to something people can watch.

If you are feeling energetic, you can try to fix the oggs directly, without reencoding. Currently the individual vorbis and theora streams are continuous, with no gaps in the streams. One way to make a synchronised mux is to make gaps in the streams at strategic places, to say that position 4:36 in the video corresponds to position 4:25 in the audio, for example. You can try do this with a resynchronizer app that I wrote, available from GStreamer CVS. The resynchronizer has some bugs, though, and probably will take some hacking.

Feel free to post comments on this page for what you have found that works and what does not work for you. Also feel free to mail me a link to a processed video so I can get it hosted.