Difference between revisions of "Digital Video Transmission"
Revision as of 09:49, 25 April 2010
- 1920 x 1080i (2-8 Mbps)
- 1280 x 720p (1-4 Mbps)
- 704 x 480p (412 kbps to 2 Mbps)
- 640 x 360 (256 kbps to 1 Mbps)
Using OGG Theora
DVB-S uses QPSK.
Gaussian minimum shift keying or GMSK is a continuous-phase frequency-shift keying modulation scheme. It is similar to standard minimum-shift keying (MSK); however the digital data stream is first shaped with a Gaussian filter before being applied to a frequency modulator. This has the advantage of reducing sideband power, which in turn reduces out-of-band interference between signal carriers in adjacent frequency channels. However, the Gaussian filter increases the modulation memory in the system and causes intersymbol interference, making it more difficult to discriminate between different transmitted data values and requiring more complex channel equalization algorithms such as an adaptive equalizer at the receiver.
GMSK has high spectral efficiency, but it needs a higher power level than QPSK, for instance, in order to transmit the same amount of data reliably.
GMSK is used in GSM as well as in Space-to-Earth links for high-rate mission data.