Bit rate
Name | Symbol | Multiple | |
---|---|---|---|
bit per second | bit/s | 1 | 1 |
Metric prefixes (SI) | |||
kilobit per second | kbit/s | 103 | 10001 |
megabit per second | Mbit/s | 106 | 10002 |
gigabit per second | Gbit/s | 109 | 10003 |
terabit per second | Tbit/s | 1012 | 10004 |
Binary prefixes (IEC 80000-13) | |||
kibibit per second | Kibit/s | 210 | 10241 |
mebibit per second | Mibit/s | 220 | 10242 |
gibibit per second | Gibit/s | 230 | 10243 |
tebibit per second | Tibit/s | 240 | 10244 |
In telecommunications and computing, bit rate (bitrate or as a variable R) is the number of bits that are conveyed or processed per unit of time.[1]
The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction with an
In most computing and digital communication environments, one byte per second (symbol: B/s) corresponds to 8 bit/s.
Prefixes
When quantifying large or small bit rates,
0.001 bit/s | = 1 mbit/s (one millibit per second, i.e., one bit per thousand seconds) |
1 bit/s | = 1 bit/s (one bit per second) |
1,000 bit/s | = 1 kbit/s (one kilobit per second, i.e., one thousand bits per second)
|
1,000,000 bit/s | = 1 Mbit/s (one megabit per second, i.e., one million bits per second)
|
1,000,000,000 bit/s | = 1 billion bits per second)
|
1,000,000,000,000 bit/s | = 1 trillion bits per second)
|
Binary prefixes are sometimes used for bit rates.[4][5] The International Standard (
In data communications
Gross bit rate
In digital communication systems, the physical layer gross bitrate,[6] raw bitrate,[7] data signaling rate,[8] gross data transfer rate[9] or uncoded transmission rate[7] (sometimes written as a variable Rb[6][7] or fb[10]) is the total number of physically transferred bits per second over a communication link, including useful data as well as protocol overhead.
In case of serial communications, the gross bit rate is related to the bit transmission time as:
The gross bit rate is related to the
For most line codes and modulation methods:
More specifically, a line code (or baseband transmission scheme) representing the data using pulse-amplitude modulation with different voltage levels, can transfer bits per pulse. A
An exception from the above is some self-synchronizing line codes, for example
A theoretical upper bound for the symbol rate in baud, symbols/s or pulses/s for a certain spectral bandwidth in hertz is given by the Nyquist law:
In practice this upper bound can only be approached for
In case of parallel communication, the gross bit rate is given by
where n is the number of parallel channels, Mi is the number of symbols or levels of the
Information rate
The
In modems and wireless systems, link adaptation (automatic adaptation of the data rate and the modulation and/or error coding scheme to the signal quality) is often applied. In that context, the term peak bitrate denotes the net bitrate of the fastest and least robust transmission mode, used for example when the distance is very short between sender and transmitter.[15] Some operating systems and network equipment may detect the "connection speed"[16] (informal language) of a network access technology or communication device, implying the current net bit rate. The term line rate in some textbooks is defined as gross bit rate,[14] in others as net bit rate.
The relationship between the gross bit rate and net bit rate is affected by the FEC code rate according to the following.
- net bit rate ≤ gross bit rate × code rate
The connection speed of a technology that involves forward error correction typically refers to the physical layer net bit rate in accordance with the above definition.
For example, the net bitrate (and thus the "connection speed") of an
The net bit rate of ISDN2 Basic Rate Interface (2 B-channels + 1 D-channel) of 64+64+16 = 144 kbit/s also refers to the payload data rates, while the D channel signalling rate is 16 kbit/s.
The net bit rate of the Ethernet 100BASE-TX physical layer standard is 100 Mbit/s, while the gross bitrate is 125 Mbit/s, due to the
In communications technologies without forward error correction and other physical layer protocol overhead, there is no distinction between gross bit rate and physical layer net bit rate. For example, the net as well as gross bit rate of Ethernet 10BASE-T is 10 Mbit/s. Due to the Manchester line code, each bit is represented by two pulses, resulting in a pulse rate of 20 megabaud.
The "connection speed" of a
The
- net bit rate ≤ channel capacity
The channel capacity is proportional to the
Network throughput
The term
Goodput (data transfer rate)
Goodput or data transfer rate refers to the achieved average net bit rate that is delivered to the application layer, exclusive of all protocol overhead, data packets retransmissions, etc. For example, in the case of file transfer, the goodput corresponds to the achieved file transfer rate. The file transfer rate in bit/s can be calculated as the file size (in bytes) divided by the file transfer time (in seconds) and multiplied by eight.
As an example, the goodput or data transfer rate of a V.92 voiceband modem is affected by the modem physical layer and data link layer protocols. It is sometimes higher than the physical layer data rate due to
If no data compression is provided by the network equipment or protocols, we have the following relation:
- goodput ≤ throughput ≤ maximum throughput ≤ net bit rate
for a certain communication path.
Progress trends
These are examples of physical layer net bit rates in proposed communication standard interfaces and devices:
WAN modems | Ethernet LAN | WLAN
|
Mobile data |
---|---|---|---|
|
|
|
Multimedia
In digital multimedia, bit rate represents the amount of information, or detail, that is stored per unit of time of a recording. The bitrate depends on several factors:
- The original material may be sampled at different frequencies.
- The samples may use different numbers of bits.
- The data may be encoded by different schemes.
- The information may be digitally compressed by different algorithms or to different degrees.
Generally, choices are made about the above factors in order to achieve the desired trade-off between minimizing the bitrate and maximizing the quality of the material when it is played.
If
The encoding bit rate of a multimedia file is its size in
For real-time
The term average bitrate is used in case of variable bitrate multimedia source coding schemes. In this context, the peak bit rate is the maximum number of bits required for any short-term block of compressed data.[17]
A theoretical lower bound for the encoding bit rate for
The bitrates in this section are approximately the minimum that the average listener in a typical listening or viewing environment, when using the best available compression, would perceive as not significantly worse than the reference standard.
Audio
CD-DA
The bit rate of PCM audio data can be calculated with the following formula:
For example, the bit rate of a CD-DA recording (44.1 kHz sampling rate, 16 bits per sample and two channels) can be calculated as follows:
The cumulative size of a length of PCM audio data (excluding a file header or other metadata) can be calculated using the following formula:
The cumulative size in bytes can be found by dividing the file size in bits by the number of bits in a byte, which is eight:
Therefore, 80 minutes (4,800 seconds) of CD-DA data requires 846,720,000 bytes of storage:
MP3
The
- 32 kbit/s – generally acceptable only for speech
- 96 kbit/s – generally used for speech or low-quality streaming
- 128 or 160 kbit/s – mid-range bitrate quality
- 192 kbit/s – medium quality bitrate
- 256 kbit/s – a commonly used high-quality bitrate
- 320 kbit/s – highest level supported by the MP3 standard
Other audio
- 700 bit/s – lowest bitrate open-source speech codec Codec2, but barely recognizable yet, sounds much better at 1.2 kbit/s
- 800 bit/s – minimum necessary for recognizable speech, using the special-purpose speech codecs
- 2.15 kbit/s – minimum bitrate available through the open-source Speex codec
- 6 kbit/s – minimum bitrate available through the open-source Opus codec
- 8 kbit/s – telephone quality using speech codecs
- 32–500 kbit/s – Ogg Vorbis
- 256 kbit/s – Digital Audio Broadcasting (DAB) MP2 bit rate required to achieve a high quality signal[18]
- 292 kbit/s – Sony Adaptive Transform Acoustic Coding (ATRAC) for use on the MiniDisc Format
- 400 kbit/s–1,411 kbit/s – Free Lossless Audio Codec, WavPack, or Monkey's Audioto compress CD audio
- 1,411.2 kbit/s – CD-DA
- 5,644.8 kbit/s – DSD, which is a trademarked implementation of PDM sound format used on Super Audio CD.[19]
- 6.144 Mbit/s – E-AC-3 (Dolby Digital Plus), an enhanced coding system based on the AC-3 codec
- 9.6 Mbit/s – DVD-Audio, a digital format for delivering high-fidelity audio content on a DVD. DVD-Audio is not intended to be a video delivery format and is not the same as video DVDs containing concert films or music videos. These discs cannot be played on a standard DVD-player without DVD-Audio logo.[20]
- 18 Mbit/s – advanced lossless audio codec based on Meridian Lossless Packing (MLP)
Video
- 16 kbit/s – videophonequality (minimum necessary for a consumer-acceptable "talking head" picture using various video compression schemes)
- 128–384 kbit/s – business-oriented videoconferencingquality using video compression
- 400 kbit/s H.264)[21]
- 750 kbit/s H.264)[21]
- 1 Mbit/s H.264)[21]
- 1.15 Mbit/s max –
- 2.5 Mbit/s H.264)[21]
- 3.5 Mbit/s typ[clarification needed] – Standard-definition television quality (with bit-rate reduction from MPEG-2 compression)
- 3.8 Mbit/s YouTube 720p60 (60 FPS) videos (using H.264)[21]
- 4.5 Mbit/s H.264)[21]
- 6.8 Mbit/s YouTube 1080p60 (60 FPS) videos (using H.264)[21]
- 9.8 Mbit/s max – MPEG2 compression)[23]
- 8 to 15 Mbit/s typ – HDTV quality (with bit-rate reduction from MPEG-4 AVC compression)
- 19 Mbit/s approximate – HDV 720p (using MPEG2 compression)[24]
- 24 Mbit/s max – MPEG4 AVC compression)[25]
- 25 Mbit/s approximate – HDV 1080i (using MPEG2 compression)[24]
- 29.4 Mbit/s max – HD DVD
- 40 Mbit/s max –
- 250 Mbit/s max – DCP (using JPEG 2000 compression)
- 1.4 Gbit/s – 10-bit 4:4:4 uncompressed 1080p at 24 FPS
Notes
For technical reasons (hardware/software protocols, overheads, encoding schemes, etc.) the actual bit rates used by some of the compared-to devices may be significantly higher than what is listed above. For example, telephone circuits using
See also
- Audio bit depth
- Average bitrate
- Bandwidth (computing)
- Baud (symbol rate)
- Bit-synchronous operation
- Chip rate
- Clock rate
- Code rate
- Constant bitrate
- Data-rate units
- Data signaling rate
- List of interface bit rates
- Measuring network throughput
- Orders of magnitude (bit rate)
- Spectral efficiency
- Variable bitrate
References
- ISBN 9788120328464. Retrieved 10 July 2011.
- ^ International Electrotechnical Commission (2007). "Prefixes for binary multiples". Archived from the original on 25 September 2016. Retrieved 4 February 2014.
- S2CID 25112828.
- ^ Schlosser, S. W., Griffin, J. L., Nagle, D. F., & Ganger, G. R. (1999). Filling the memory access gap: A case for on-chip magnetic storage (No. CMU-CS-99-174). CARNEGIE-MELLON UNIV PITTSBURGH PA SCHOOL OF COMPUTER SCIENCE.
- ^ "Monitoring file transfers that are in progress from IBM WebSphere MQ Explorer". 11 March 2014. Retrieved 10 October 2014.
- ^ ISBN 9783642013591. Retrieved 10 July 2011.
- ^ ISBN 9780470779439. Retrieved 10 July 2011.
- ISBN 9781602670006. Retrieved 10 July 2011.
- ^ ISBN 9780071382823. Retrieved 10 July 2011.
- ]
- ^ Lou Frenzel. 27 April 2012, "What's The Difference Between Bit Rate And Baud Rate?". Electronic Design. 2012.
- ^ Theodory S. Rappaport, Wireless communications: principles and practice, Prentice Hall PTR, 2002
- ^ Lajos Hanzo, Peter J. Cherriman, Jürgen Streit, Video compression and communications: from basics to H.261, H.263, H.264, MPEG4 for DVB and HSDPA-style adaptive turbo-transceivers, Wiley-IEEE, 2007.
- ^ a b V.S. Bagad, I.A. Dhotre, Data Communication Systems, Technical Publications, 2009.
- ^ Sudhir Dixit, Ramjee Prasad Wireless IP and Building the Mobile Internet, Artech House
- ^ Guy Hart-Davis,Mastering Microsoft Windows Vista home: premium and basic, John Wiley and Sons, 2007
- ^ Khalid Sayood, Lossless compression handbook, Academic Press, 2003.
- ^ Page 26 of BBC R&D White Paper WHP 061 June 2003, DAB: An introduction to the DAB Eureka system and how it works http://downloads.bbc.co.uk/rd/pubs/whp/whp-pdf-files/WHP061.pdf
- ^ Extremetech.com, Leslie Shapiro, 2 July 2001. Surround Sound: The High-End: SACD and DVD-Audio. Archived 30 December 2009 at the Wayback Machine Retrieved 19 May 2010. 2 channels, 1-bit, 2822.4 kHz DSD audio (2×1×2,822,400)= 5,644,800 bits/s
- ^ "Understanding DVD-Audio" (PDF). Sonic Solutions. Archived from the original (PDF) on 4 March 2012. Retrieved 23 April 2014.
- ^ a b c d e f g "YouTube bit rates". Retrieved 10 October 2014.
- ^ "MPEG1 Specifications". UK: ICDia. Retrieved 11 July 2011.
- ^ "DVD-MPEG differences". Sourceforge. Retrieved 11 July 2011.
- ^ a b HDV Specifications (PDF), HDV Information, archived from the original (PDF) on 8 January 2007.
- ^ "Avchd Information". AVCHD Info. Retrieved 11 July 2011.
- ^ "3.3 Video Streams" (PDF), Blu-ray Disc Format 2.B Audio Visual Application Format Specifications for BD-ROM Version 2.4 (white paper), May 2010, p. 17.
External links
- Live Video Streaming Bitrate Calculator Calculate bitrate for video and live streams
- DVD-HQ bit rate calculator Calculate bit rate for various types of digital video media.
- Maximum PC - Do Higher MP3 Bit Rates Pay Off?
- Valid8 Data Rate Calculator