Video for Mobile Device Mark Green School of Creative Media

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

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

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

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

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

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

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

Video Formats  Phones have several constraints: not very much memory for storing video not very much memory for storing video slow transmission rates slow transmission rates maximum MMS message limited to 100KByte 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

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

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

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

Production - Phone

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

Production - PDA