08-16-2017, 09:41 PM
The video can be transmitted over several kinds of networks such as IP networks, GSM networks(low bandwidth), wireless networks etc. Taking the case of a GSM network, they are unable to deliver video telephony services due to their characteristic narrow bandwidth at 9.6 kilo bits per sec (kbps). But 3G networks can transmit data at a rate of 64 kbps, and thus is more suitable for the transmission of video data. Certain adjustments are made for bandwidth saving. Sometimes, in the absence of audio data, such as silence during a voice conversation, the audio transmission is temporarily turned off. The bandwidth that would have otherwise been kept apart for audio transmission is made available for use for transmitting video frames on the GSM network.By combining video conferencing protocols like H.324 or its variants, 3G/324M, video and audio transmission of acceptable quality over the low bit rate GSM network can be achieved.
Transmission over lossy networks
For MPEG and H.26x, the compressed bitstream is fragile in the face of channel loss which is a direct consequence of the prediction-based coding framework that underlies these codecs. Targeting backward compatibility with standard predictive video codecs, a system based on principles from distributed source coding. Extra information is sent over a lower-rate auxiliary channel to correct for errors in the decoded frame and eliminte the drift. Packet losses thus lead to predictor mismatch or drift between encoder and decoder.
Transmission over IP networks
Video transmission of live TV broadcasts requires high-quality and low-delay video. Standardized and stable IP technology enables broadcasts such as multicast over a low-cost network system. ultra-broadband IP network allows video transmission over an IP network, and this provides the next-generation video transmission method for broadcasting stations.