Video for Mobile Device

1. Video for Mobile Device Mark Green School of Creative Media

2. Introduction • Video is new on mobile devices • not supported by many phones, mainly recent high end phones • supported on most recent PDAs • standards for video on mobile devices are relatively new, so there are still a lot of surprises

3. Video Source • Prepare video in standard way, try to maintain quality in all steps • think about the display device, governs what you can do • relatively low resolution, must avoid details they will not appear in final video • small objects can cause popping problems, try to avoid them

4. Video Source • Want to have large objects, relatively uniform colours • can’t do much text, won’t be readable • for titles keep them short, a few words in large font • subtitles aren’t possible, do separate version for each language with appropriate sound track

5. Video Source • Use bright video, screens may not be bright and may not have much contrast • can’t control viewing environment, may be in bright sunlight! • In general keep the content simple • audio is even harder, particularly on mobile phones, not designed for good audio

6. Video Source • Mobile phones don’t have stereo, only a mono feed • PDAs have a single speaker, without headphones don’t have stereo • on phones sampling rate is 16Khz or lower, CD quality sound is 44.1KHz • not very good for music, but okay for speech

7. Video Source • Need to keep sound track simple • may want to avoid background music, or rely on something quiet with low frequencies • probably want to just use speech, clear and not very fast

8. Video Formats • Players support very few formats, not like PC players that can play almost anything • each format requires space for program code, space is limited, so try to have as few formats as possible • phones seem to be standardising on 3gp, a low bit rate format

9. Video Formats • Phones have several constraints: • not very much memory for storing video • slow transmission rates • maximum MMS message limited to 100KByte • maximum bit rate is 64Kb, compare to VCD bit rate of approximately 1.5Mb • there will be a significant difference in quality

10. Video Formats • For PDAs can use Windows Media player or Real player, both use different formats • both support only their native formats • will only look at Windows Media player, it only supports .wmv files for video and supports .wma for audio • much better quality than phones

11. Production • Use standard production techniques to produce the video in a standard format (avi for example) • work at medium resolution, don’t need high resolution • use encoder to produce video format for the particular device

12. Production - Phone • Use Nokia Multimedia converter to produce a 3gp file for phones • can control the bit rate and fps of the resulting file • can also specify maximum file size and converter will compute the bit rate and fps that will produce that file size

13. Production - Phone

14. Production - PDA • Use Windows Media Encoder to produce the video file • encoder supports a much wider range of formats, this gives us more choice, but we could produce a file that won’t play! • Can source from a file or camera and can stream the output

15. Production - PDA