The FAQ For DVR
Q1: What is H.264 compression?
A : H.264 is a new video compression scheme that is becoming the worldwide digital video standard for consumer electronics and personal computers. In particular, H.264 has already been selected as a key compression scheme (codec) for the next generation of optical disc formats, HD-DVD and Blu-ray disc (sometimes referred to as BD or BD-ROM) H.264 has been adopted by the Motion Picture Experts Group (MPEG) to be a key video compression scheme in the MPEG-4 format for digital media exchange. H.264 is sometimes referred to as MPEG-4 Part or as MPEG-4 Specification Advanced Video Coding.This new compression scheme has been developed in response to technical factors and the needs of an evolving market:
1.MPEG-2 and other older video codecs are relatively inefficient.
2.Much greater computational resources are available today.
3.High Definition video is becoming pervasive, and there is a strong need to storeand transmit more efficiently the higher quantity of data of HD (about 6 times more than Standard Definition video).
Q2: What is MJPEG Motion JPEG Video Codec?
Bitstream encoding for video in which each frame [or field?] is compressed using the JPEG still-image compression algorithm. Taken as a sequence, the series of frames represent the source video. MJPEG bitstreams are often wrapped in AVI files where they carry the Four-Character Code.
Q3: What is Bit Rate?
A : The amount of compressed video data delivered into the decoding system. The higher the bit-rate, the higher the quality and/or the resolution of the video. For optical disc formats, this is usually measured in megabits per second (Mbps).
Q4: What would the bandwidth be for different Video Media?
A : HDV Video (high resolution video recorded on mini DV tape as MPEG-2)
HDV-1 at 720p: 19 MBit/s
HDV-2 at 1080i: 25 MBit/s
Computer Graphics SXGA (1280 x 1024 @ 60Hz):
pixel clock of 108 MHz, color depth 24 bit => 2.6 Gbps
High Quality Video (not compressed):
Digital Data = 30 frames per second / 640 x 480 pixels / 24-bit color / pixel => 221 Mbps
Reduced Quality Video (not compressed):
Digital Data = 15 frames per second / 320 x 240 pixels / 16-bit color / pixel => 18 Mbps
Reduced Quality Video (16bit color), 16 frames per second, 320 x 240 pixel x 16 bits x 16 frames = 19,660,800 bits per second => 19.7 Mbps
Videoconferencing: 64 kbps to 3 Mbps
Corporate Video:2 Mbps to 3 Mbps
MPEG-1 Video:1 to 3 Mbps
MPEG-2 Video:
- Compression 35 : 1 - 16 : 1 (Quality for Presentation Purpose) 5 - 10 Mbps
- Compression 16 : 1 - 7 : 1 (Betacam SP Replacement) 10 - 25 Mbps
- Compression 7 : 1 - 2 : 1 (Spectacular Imaging) 25 - 90 Mbps
- Compression 40 : 1 - 16 : 1 (DVD) 3.5 - 10 Mbps
CD Quality Audio:
44,1 kHz sample rate / 16-bit samples / 2 audio channels = 1.4 Mbps
Low Quality Audio:
11,05 kHz sample rate / 8-bit samples / 1 audio channel = 0.1 Mbps
MPEG-1 Audio, Layer 3 (MP3), "near CD-quality": 96 to 256 kbps
Computer Data:
10BaseT Ethernet: 10 Mbps
100BaseT Ethernet: 100 Mbps
1Gigabit Rthernet: 1 Gbps
FireWire: 400 Mbps
FireWire (new): 800 Mbps
USB (1.1): 12 Mbps
USB (2.0): 480 Mbps
Fibre Channel FC: 1 Gbps .. 4 Gbps
Fibre Channel (new developments coming up): 40 Gbps
Computer PCI Bus: 132 Mbps
14.4 modem: 1.44 kbyte/sec
28.8 modem: 2.88 kbyte/sec
ISDN: 6.4 kbyte/sec to 15.44 kbyte/sec (std MPEG1)
ATM: 45 to 155 Mbps
(Mbps = Megabits per second)
Mbps stands for millions of bits per second and is a measure of bandwidth. It represents the total information flow over a given time on a communications medium.
A megabit is a million binary pulses or "bits".
Sometimes 1 Mbps is defined as 1,048,576 bits. But bits in data communications have historically been counted using the decimal number system. This would mean, 1 Mbps is 1.000.000 bits per second, and 28.8 kilobits is 28,800 bits per second.
Bandwidth (the width of a band of electromagnetic frequencies) is used to mean how fast data flows on a given transmission path, and the width of the range of frequencies that an electronic signal occupies on a given transmission medium. In digital systems, bandwidth is expressed as data speed in bits per second.