A Movie Player for J2ME devices (B/W)

published earlier on 15-08-2002. 

Introduction:

Everyone is really amazed by the new technologies we are having “at our hands” everyday, and by how much they are changing our lives. I think one of the notable changes in this year, was the wide introduction of java-enabled mobile phones to users around the world, and along with it many games and applications. Phones are really becoming personalized devices.

Users usually are not satisfied with playing only some old-style and silly games, they are always asking for more, they want always better games and faster graphics, although most devices feature only two colors, and a very limited speed.

             In this market of huge expansion, ZGroup company (www.zgroup-mobile.com) has thought about multimedia applications, and the first application that comes to the mind when talking about multimedia is a movie player. We remarked that the market lacked such an application; except of coarse of several programs that were given a title similar to movie player, although they were no more than image-sliders. The key difference that distinguishes a movie player is that it doesn’t display a series of images on the screen, but it will actually use the previous frame to construct the actual frame (in other words, takes into account the correlation between frames that constitute a film), thus diminish the required space and bandwidth.

Development:

            When we started writing our movie player, we had several problems that needed a solution:

  1. Limited color depth: more than 75% of java-enabled mobiles feature only two colors display, which makes the movies really difficult to view.

  2. Limited resolution: MIDP standard forces mobiles to have at least a 96x64 pixels, and the problem is that you can’t see of much at this resolution. Another important factor is the real dimension of the pixel, which is relatively big when compared to the dimension of a pixel of our usual screens.

   3. Slow Java implementation on most machines.

   4. MIDP 1.0 specification doesn’t provide a good interface to write directly on the screen, whereas most phone companies feature a specific API to do so. So if we wanted our movie player to work on all phones, we have to write a specific format, which should be easy to display in the MIDP specification. 

     Taking all these facts into consideration, it was evident that we should develop our own movie’s format that suits the mobile best. It’s really impossible at the current stage to let users watch their favorite movies in MPEG formats on the mobile du to speed and memory limitations. So we had to create a conversion program that can convert movies from PC formats to our own format. The new format will support only two colors and the compression method should feature high compression, and fast decompression. We had also to write a new midlet that can read this format and decompress it.

 Results:

We have three different favours of this midlet:

1.      Siemens optimized version:

Will run raw data files at 12fps, and will run compressed movies at 4fps (still improving).

2.      Nokia optimized versoin:

   Has the same performance of Siemens version. 

3.      MIDP compatible version:

   It will run on any MIDP device. It’s fairly fast but with low quality.

 Of coarse, our three versions support playing movies on the net. It’s important since most devices don’t have storage capabilities. The needed bandwidth is about 9600bit/sec for compressed movies.

The advantages to other movies players on the market are:

1.      Fast-loading: since most movie players are merely an image-slider, so the midlet will be slow to start.

2.      Smaller-files: Our files are much more smaller than the .png images of other image-sliders. This will reduce required storage space as well as required band-width.

3.      Faster playing: On our benchmark, we have reached a 13fps for the mrd files on an SL45i. Whereas the .png sequencer are much more slower.

4.      Watching movies on the net: not possible with image-sliders (very slow).

Conversion Program:

      ZGroup has decided lately to publish the conversion program for the zMoviePlayer. You can find an alpha release at: http://www.zgroup-mobile.com/ZMP. We will be updating this regularly. If you have any comment about the midlet, the converter. . . . etc please send it to zmp@zgroup-mobile.com. Also you can send us your movies to movies@zgroup-mobile.com so that we might include them in our website.

 Other Applications:

The most evident application of this software is to enable users to view some clips on their mobiles. But there is more to that, and imagination only limits its usability. For example we can (based on our software) develop a WEB-CAM application, which allow users to view their CAMs using their phones. Also this application is a must for teleconferencing.

Future imporvements:

          Actually we are still not satisfied with our results. Although our current version is the best in the market, still we have a long way to go. We are currently working at:

1.      The quality of images is not perfect, and we are trying to improve it.

2.      We are working on a color version of the player, which should be available for Nokia 7210, 7650 devices soon.

3.      We are always trying to improve performance and compression.