Helix media activity

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Description & Goals

Summary

Watch & Listen is a media player based on the Helix Media Engine. The Helix engine uses a plugin system to provide compatibility with a wide array of formats. By default Watch & Listen will ship with only free codecs, separate bundles are available for non-free codecs.

Currently, the activity is bundled with the Helix media engine all in one package for easy installation. Eventually this engine, and the python bindings providing access to it will be moved to a location allowing any activity to easily use the media engine.

Goals

Give children access to multimedia content

Collaboration

Collaboration is not available with Watch & Listen at this time due to technical limitations. The collaboration scenario envisioned is multiple children viewing the same media in sync. There are two methods for achieving this.

Method 1: Multicasting

The player upon starting sharing would multicast the media file to other laptops. The XO is simply not powerful enough to stream a file to other laptops even if it does not require reencoding. There is also a question of bandwidth usage when 1 or more laptops are multicasting over the mesh network.

Method 2: Synchronized Viewing

This method would synchronize the players on multiple laptops so that they are all at the same time in the file. This requires that all children have the file locally. The bigger issue is without multicasting the file it will be very hard to synchronize all players closely enough that there is no audio overlap between laptops (sounds like echos)

Helix Activity Installation Notes

  • You can download a packet of videos to go along with it. If you're downloading something larger than 15MB, you should do it from the command line via wget; downloads via the browser currently go to /tmp and use up memory. Use the open location button (see below) to browse to these files. A good place to find some ogg videos to test with is wikimedia:
    http://commons.wikimedia.org/wiki/Category:Video

We will be adding more content as it becomes available (email us, olpc-player-dev at helixcommunity.org with suggestions, or leave them here on the discussion page)

Helix "Watch & Listen" Media Activity Usage Notes

Please refer to this screen grab of the activity running:

http://staff.osuosl.org/~schonstal/watch_and_listen.png

Starting at the upper left and going right you have the following buttons and functions:

  • Previous button.
  • Play/pause button.
  • Stop button.
  • Next button.
  • Repeat button.
  • Progress bar - This shows the current time and total duration of the clip. You can also seek through a media clip by clicking and dragging.
  • Full Screen button
  • Native Size Toggle Button - use this to toggle the size of the video between fit-to-screen and native size

On the bottom of the player you have:

  • Buffering/Stats Label - This displays buffering information, as well as title and author of the currently playing clip.

The activity has not been through QA (so YMMV), but this version of the engine should support (note that currently the activity only ships with the Ogg Vorbis and Ogg Theora codec installed):

  • 3GPP-Rel6 file parsing and 3GPP-Rel6 audio and video playback
  • 3G2 audio depacketizers and QCelp decoder hooks
  • AAC and aacPlus decoder - More info
  • AAC and aacPlus playback from .3gp, .m4a, .aac or .ra files and 3GPP, ISMA or ice-cast streams
  • SDP file parsing
  • TimedText from .3gpp files

Supported Media Formats

Watch & Listen can play any format that has a Helix Plugin. Not all plugins are GPL and patent free. By default only the free codecs will be shipped. Packages including non-free codecs will also be available.

Free Codecs

All of these codecs are completely open source and patent free.

  • Ogg Vorbis and Ogg Theora (with some known problems streaming over RTSP).
  • Uncompressed PCM from .wav, avi, .aiff or .au files and standard RTP streams
  • PCM a-law and u-law from .wav, avi or .au files and standard RTP streams
  • SMIL 1.0/2.0 multimedia
  • Still images (JPEG, GIF, PNG, WBMP)
  • Text - plain from .txt files

Helix Licensed Codecs

Per an agreement with RealNetworks all RealMedia formats are available for use on the olpc.

  • RealAudio/RealVideo Codecs
  • RealAudio and RealVideo playback from RealMedia file format and RealMedia streams.
  • RAM metafile parsing and playback
  • RealEvents and RealImageMap from .rm files and RealMedia streams
  • RealText from .rt files and RealText streams

Non-Free Codecs

Helix Plugins are available for these formats but they have patents associated with them.

  • I420 video rendering
  • MJPEG video playback from .avi files
  • MP3 audio playback from .mp3 files, standard RTP streams and shout-cast streams
  • MP3 playlist parsing and playback
  • Helix MP3 Decoder
  • Helix MP3 Encoder
  • AMR-NB and AMR-WB audio playback from .3gp and .amr files and 3GPP streams
  • RGB video from .avi files
  • H.261 video from standard RTP streams
  • H.263 video from .3gp files and standard RTP streams
  • H.264 video from .3gp files and standard H.264 RTP streams
  • MPEG1/2 file parsing
  • MPEG4 audio (no video) playback from .mp4 or .3gp files and ISMA or 3GPP streams

Helix "Watch & Listen" Media Activity Version 10 Bugs

Here is a list of bugs and limitations of the current implementation:

  • This isn't entirely free software. The Helix DNA Client and the Helix Player are licensed under the GNU General Public License (GPL) free and open source license. However, some plugins use formats that have patents associated with them and are not free to use.
  • No obvious playable media files -- not even a two second "It works" ogg recording -- are shipped with the software.
  • no keybindings.

Tips and tricks

Running the Helix activity from the command line

It is often useful to directly launch the media player from the command line. In particular, many programs (web browsers, file managers, etc.) can be configured to use this command for opening media files, which does not work with sugar's activities. The command line tool can also be used directly to play streaming media by passing to it the URL of the media stream.

Follow the below steps to achieve that (note that, using a three-button USB mouse, you can paste selected texts to the terminal with the middle button):

  • Install the Helix media activity as described above
  • Open a terminal activity.
  • Execute the following command:
nano helixplay
  • In the text editor window, paste the following content (using the middle-button of your USB mouse after selecting this text in the browser window):
#!/bin/sh
#
# helixplay
#
# Runs the Watch & Listen Activity from the command line. A specified URI
# is used.  The activity is run in the background.
#
# Usage:
# helixplay [URI]
#
# Example:
# helixplay http://www.radioparadise.com/musiclinks/rp_128-1.ram
#
# This script is basically a shortcut for the following command:
# SUGAR_BUNDLE_PATH=/home/olpc/Activities/Watch\ \&\ Listen.activity sugar-activity MediaPlayerActivity.MediaPlayerActivity -b org.osl.MediaPlayerActivity -a fakeactivityid -u [uri] &

SUGAR_BUNDLE_PATH=/home/olpc/Activities/Watch\ \&\ Listen.activity
_ACTIVITY=MediaPlayerActivity.MediaPlayerActivity
_BUNDLE=org.osl.MediaPlayerActivity
_ACTIVITY_ID=fakeactivityid

sugar-activity ${_ACTIVITY} -b ${_BUNDLE} -a ${_ACTIVITY_ID} -u $@ &
Take care not to introduce line breaks when copying. Afterwards, press CTRL+X and confirm the file safe.
  • Execute the following command to make that file an executable script:
chmod 775 helixplay

This finishes the setup. You can test the activity by executing 

./helixplay http://www.radioparadise.com/musiclinks/rp_128-1.ram

(or whatever radio you like). If you followed the above steps, your file helixplay now resides in our home directory (/home/olpc/). The full path is needed to launch the program from another application.

Playing streaming media in web browsers

After enabling the command-line execution of helix, it can also be used as a streaming media plugin in the Opera web browser, so that you can just click on stream URLs to play them, as usual. To do that, first install the Helix command-line script as described above, and install Opera as described on its page in this wiki. Once Opera has been installed, you need to configure the streaming audio player:

  1. Click the O in the upper-left hand corner of the screen.
  2. Go to Tools\Preferences\
  3. Click the "Advanced" Tab
  4. Click "Downloads"
  5. Click the "Add..." button.
  6. Enter "audio/x-pn-realaudio" under MIME type (do not enter the quotes)
  7. Enter "ram,ra" under "File extension(s)"
  8. Click the radio button to the left of "Open with other application"
  9. Enter the following data in the text box beneath "Open with other application": /home/olpc/helixplay
  10. Click the check box next to "Pass web address directly to application".
  11. Click OK twice to close all dialogs

Clicking on a real media stream URL should now launch the Helix player to play it. In addition to real media streams, you can also configure further content types to be played with Helix. In general, it might often suffice to click on a new media type: Opera then asks you what to do with it and you can use similar settings above.

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