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More on movlog  
Tuesday, 17 May 2005

In my previous post, I mentioned movlog as a mobile form of video blogging. Well, that only covered the producer side of blogging, and, of course, blogging is both a producer and consumer activity (well, it should be). Furthermore, it was not completely automated, but not too painful either with the tools I have built up for myself.

Now, I need to explain how I stream my vlog subscriptions to my mobile phone. I combined my previous work on my bashpodder script with things I learned on my new job along with mplayer. After bashpodder downloads the video RSS enclosure, a script uses Mplayer to read just about any downloadable video format, scale it, and pad it to maintain aspect ratio. The Mplayer/Mencoder output is in an intermediate format. Then, the script usees the ffmpeg- and GPAC-based toolchain we use at work to conform the clips to 3GPP format: a Quicktime movie containing MPEG-4 audio and video. It uses a modified version of the MP4Box utility that comes in gpac, in order to generate hint tracks. Finally, the script puts the videos into the Darwin Streaming Server directory and builds minimal web pages to browse the daily new clips. The modified version of MP4Box implements LATM hinting for the AAC audio track. I am working on an updated patch for submission to GPAC, but ours is sorely out-of-date for submission as-is.

If you have a Sprint PCS multimedia phone, enter or SMS this URL: http://dennedy.org/~ddennedy/vlogs/. The streams are standards-based RTSP streams, but the web pages contain rtsp:// links, which most general computer web browsers do not understand. It seems the web browsers in many multimedia mobile phones (at least Sprint ones) can launch the native media player when you click these links. You can access this link with your computer browser and view the pages, but you will need to manually copy the link into Quicktime Player to stream them.

I am not sure what Linux-based players can play these streams. I have an oddly-concocted player I constructed using live.com openRTSP, named pipes, and ffplay I use during testing because openRTSP and ffplay can generate ample amounts of debug logging. I need to rebuild mplayer against live.com and see if it can play them. Also, mp4player from MPEG4IP is not liking the audio stream; not sure why right now.

Update: Quicktime Player on my Windows machine does not play the audio track. I compiled MPlayer against live.com, and it does play the audio and video although the audio is choppy.