Digital Video for Digital Devices
Aspects for Consideration
- Adoption: Is it commonplace?
- Ease of Use: Can users's play
it back with no trouble?
- Appropriateness: Digital Video
file types can have specific applications (web,device)
- Ease of Authoring
- Licensing
Frame rate
- NTSC video (broadcast) is 29.97
fps, but we round off to 30
- Film is 24 fps
- Minimum frame rate before we percieve
individual frames is 12
- Most Web Video is 15 fps
Data Rate
Data Rate is measured in either kilobits/sec
(such as a 56kb/s modem) or KiloBytes/sec. We usually divide/muliply by 8 for
conversion, but it's not accurate.
http://homepage.ntlworld.com/robin.d.h.walker/cmtips/speed.html#kilobytes
Data rate is a function of limitations
of transport.
380 kb/s = 4x CD Rom
3.5 mb/s = DV video
http://www.adobe.com/support/techdocs/a60a.htm
Size DOES Matter
- NTSC video, being analog, does
not map readily to digital frame sizes.
- Most digital video systems target
between 352x240 and 704x480 for TV reproduction
- HDTV Systems have a myriad of
frame sizes, and can be interlaced or progressive scan
Suggested frame sizes:
Web Video: (28.8) 160x120, (DSL)
240x180, 320x240
CDRom: (2x) 160x120, 8X (320x240
- 480x360 -- perhaps bigger)
Which Compression to use?
RealMedia
- Low Bandwidth Friendly
- Unique Delivery Technology supports
multiple bandwidths
- High Quality Video Compression
- Can't be edited easily
- Not Quite Open Source Helix Technology
(player, encoder, server)
Windows Media
Apple Quicktime
- Not particularly low bandwidth
friendly
- Nice Video at higher bandwidths
- Rich Feature Set: arbitrary frame
sizes, hotspots, wired sprites, Flash support, etc.
- Modular architecture supports
many codecs, including MPEG-4, MPEG-3, Sorenson, DV
- Open Source Streaming Server,
but no open source playback technology
- Well integrated with Apple's Content
Creation tools (Surprise!)
Divx
- Open Source and Commercial Implementations
- Originally derived from Microsoft's
own compression technology, but most implementations are legacy free
- Lack of standards means not all
Divx players work with all Divx content
- Some commercial adoption
- Not really designed for web delivery
- Divx.com -- The free Divx Pro
installs adware on your machine. The plain free Divx installer works, but
watermarks your files.
http://www.divx.com
MPEG -1
- Not low bandwidth friendly
- Common as dirt, even Palm Pilots
can play it back
- Lots of compression technology
options
MPEG-2
- Strictly mid to high bandwidth
- Can be CPU intensive for decoding
- Amalgation of Licensed Technologies
MPEG-4
- Licensed technology
- Modular nature much like Quicktime
- Scalable from very low bandwidth
(cell phone) to near DVD quality
- Many implementations, supported
by RealMedia, Quicktime (incomplete) and others
- Better quality codecs (h264) just
becoming available
Essential Tools
Virtual Dub: Windows Media transcoder,
simple editor. Use to encode Divx content, clean up noisy footage, etc.
http://www.virtualdub.org/
Quicktime Pro: edit, transcode, filter,
composite, etc. Buy the MPEG-2 Plug in, and you can transcode MPEG-2 content
as well.
http://www.apple.com/quicktime/
RealMedia Producer (use the free
one)
http://www.realnetworks.com/products/producer/index.html
RealMedia Export Plugin for Quicktime
https://helixcommunity.org/2004/real10export
TMPGENC: Excellent Windows based
MPEG-1/MPEG-2 encoder.
http://www.tmpgenc.net/e_main.html
Windows Media Encoder Download Page
http://www.microsoft.com/windows/windowsmedia/9series/encoder/default.aspx
This document is available at:
http://www.ncsu.edu/it/multimedia/vidcompression.html