Editing Bit rate (section)

== Multimedia <span class="anchor" id="Bitrates in multimedia"></span><span class="anchor" id="Multimedia encoding bit rate"></span> ==
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 [[data compression|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 [[lossy data compression]] is used on audio or visual data, differences from the original signal will be introduced; if the compression is substantial, or lossy data is decompressed and recompressed, this may become noticeable in the form of [[compression artifact]]s. Whether these affect the perceived quality, and if so how much, depends on the compression scheme, encoder power, the characteristics of the input data, the listener's perceptions, the listener's familiarity with artifacts, and the listening or viewing environment.

The encoding bit rate of a multimedia file is its size in [[bytes]] divided by the playback time of the recording (in seconds), multiplied by eight.

For real-time [[streaming multimedia]], the encoding bit rate is the [[goodput]] that is required to avoid playback interruption.

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.<ref>Khalid Sayood, [https://books.google.com/books?id=LjQiGwyabVwC&dq=%22peak+bit+rate%22&pg=PA264 Lossless compression handbook], Academic Press, 2003.</ref>

A theoretical lower bound for the encoding bit rate for [[lossless data compression]] is the [[source information rate]], also known as the ''entropy rate''.

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.<!-- PLEASE understand the above sentence before making changes. References to controlled tests would be valuable. But this discussion really belongs elsewhere. -->

=== Audio ===

==== CD-DA ====
[[Compact Disc Digital Audio]] (CD-DA) uses 44,100 samples per second, each with a bit depth of 16, a format sometimes abbreviated like "16bit&nbsp;/&nbsp;44.1kHz". CD-DA is also [[Stereophonic sound|stereo]], using a left and right [[Audio channel|channel]], so the amount of audio data per second is double that of mono, where only a single channel is used.

The bit rate of PCM audio data can be calculated with the following formula:
: <math>\text{bit rate} = \text{sample rate} \times \text{bit depth} \times \text{channels}</math>

For example, the bit rate of a CD-DA recording (44.1&nbsp;kHz sampling rate, 16 bits per sample and two channels) can be calculated as follows:
: <math>44,100 \times 16 \times 2 = 1,411,200\ \text{bit/s} = 1,411.2\ \text{kbit/s}</math>

The cumulative size of a length of PCM audio data (excluding a file [[Header (computing)|header]] or other [[metadata]]) can be calculated using the following formula:
: <math>\text{size in bits} = \text{sample rate} \times \text{bit depth} \times \text{channels} \times \text{time}.</math>

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:
: <math>\text{size in bytes} = \frac{\text{size in bits}}{8}</math>

Therefore, 80 minutes (4,800 seconds) of CD-DA data requires 846,720,000 bytes of storage:
: <math>\frac{44,100 \times 16 \times 2 \times 4,800}{8} = 846,720,000\ \text{bytes} \approx 847\ \text{MB} \approx 807.5\ \text{MiB}</math>
where '''MiB''' is mebibytes with [[binary prefix]] Mi, meaning 2<sup>20</sup> = 1,048,576.

==== MP3 ====
The [[MP3]] audio format provides [[lossy data compression]]. Audio quality improves with increasing bitrate:
* 32&nbsp;kbit/s{{snd}} generally acceptable only for speech
* 96&nbsp;kbit/s{{snd}} generally used for speech or low-quality streaming
* 128 or 160&nbsp;kbit/s{{snd}} mid-range bitrate quality
* 192&nbsp;kbit/s{{snd}} medium quality bitrate
* 256&nbsp;kbit/s{{snd}} a commonly used high-quality bitrate
* 320&nbsp;kbit/s{{snd}} highest level supported by the [[MP3]] standard

==== Other audio ====
* 700&nbsp;bit/s{{snd}} lowest bitrate open-source speech codec [[Codec2]], but Codec2 sounds much better at 1.2&nbsp;kbit/s
* 800&nbsp;bit/s{{snd}} minimum necessary for recognizable speech, using the special-purpose [[FS-1015]] [[speech encoding|speech codecs]]
* 2.15&nbsp;kbit/s{{snd}} minimum bitrate available through the open-source [[Speex]] codec
* 6&nbsp;kbit/s{{snd}} minimum bitrate available through the open-source [[Opus (audio format)|Opus]] codec
* 8&nbsp;kbit/s{{snd}} [[telephone]] quality using speech codecs
* 32–500&nbsp;kbit/s{{snd}} [[Lossy compression|lossy audio]] as used in [[Ogg Vorbis]]
* 256&nbsp;kbit/s{{snd}} Digital Audio Broadcasting ([[Digital Audio Broadcasting|DAB]]) [[MPEG-1 Audio Layer II|MP2]] bit rate required to achieve a high quality signal<ref>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</ref>
* 292&nbsp;kbit/s{{snd}} Sony [[Adaptive Transform Acoustic Coding]] (ATRAC) for use on the [[MiniDisc|MiniDisc Format]]
* 400&nbsp;kbit/s–1,411&nbsp;kbit/s{{snd}} [[Lossless compression|lossless audio]] as used in formats such as [[Free Lossless Audio Codec]], [[WavPack]], or [[Monkey's Audio]] to compress CD audio
* 1,411.2&nbsp;kbit/s{{snd}} [[Linear PCM]] sound format of [[CD-DA]]
* 5,644.8&nbsp;kbit/s{{snd}} [[Direct Stream Digital|DSD]], which is a trademarked implementation of [[Pulse-density modulation|PDM]] sound format used on [[Super Audio CD]].<ref>Extremetech.com, Leslie Shapiro, 2 July 2001. ''Surround Sound:'' [http://www.extremetech.com/article2/0,2845,1180143,00.asp ''The High-End: SACD and DVD-Audio''.] {{webarchive|url=https://web.archive.org/web/20091230154914/http://www.extremetech.com/article2/0%2C2845%2C1180143%2C00.asp |date=30 December 2009 }} Retrieved 19 May 2010. 2 channels, 1-bit, 2822.4&nbsp;kHz DSD audio (2×1×2,822,400)= 5,644,800&nbsp;bits/s</ref>
* 6.144&nbsp;Mbit/s{{snd}} E-AC-3 (Dolby Digital Plus), an enhanced coding system based on the AC-3 codec
* 9.6&nbsp;Mbit/s{{snd}} [[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.<ref>{{cite web |archive-url=https://web.archive.org/web/20120304060434/http://patches.sonic.com/pdf/white-papers/wp_dvd_audio.pdf |url=http://patches.sonic.com/pdf/white-papers/wp_dvd_audio.pdf |title=Understanding DVD-Audio |publisher=Sonic Solutions |access-date=23 April 2014 |archive-date=4 March 2012 }}</ref>
* 18&nbsp;Mbit/s{{snd}} advanced lossless audio codec based on [[Meridian Lossless Packing]] (MLP)

=== Video ===
* 16&nbsp;kbit/s{{snd}} [[videophone]] quality (minimum necessary for a consumer-acceptable "talking head" picture using various video compression schemes)
* 128&ndash;384&nbsp;kbit/s{{snd}} business-oriented [[videoconferencing]] quality using video compression
* 400&nbsp;kbit/s [[YouTube]] 240p videos (using [[H.264]])<ref name="youtube">{{cite web|url=https://support.google.com/youtube/answer/2853702?hl=en | title =YouTube bit rates |access-date=10 October 2014}}</ref>
* 750&nbsp;kbit/s [[YouTube]] 360p videos (using [[H.264]])<ref name="youtube"/>
* 1&nbsp;Mbit/s [[YouTube]] 480p videos (using [[H.264]])<ref name="youtube"/>
* 1.15&nbsp;Mbit/s max{{snd}} [[VCD]] quality (using [[MPEG-1|MPEG1]] compression)<ref>{{cite web|url=http://www.icdia.co.uk/cdprosupport/encoding/pink/mpeg1_specs.htm | title = MPEG1 Specifications |publisher=ICDia | location = UK |access-date=11 July 2011}}</ref>
* 2.5&nbsp;Mbit/s [[YouTube]] 720p videos (using [[H.264]])<ref name="youtube"/>
* 3.5&nbsp;Mbit/s typ{{Clarify|date=August 2022}}{{snd}} [[Standard-definition television]] quality (with bit-rate reduction from MPEG-2 compression)
* 3.8&nbsp;Mbit/s [[YouTube]] 720p60 (60 [[Frame rate|FPS]]) videos (using H.264)<ref name="youtube"/>
* 4.5&nbsp;Mbit/s [[YouTube]] 1080p videos (using [[H.264]])<ref name="youtube"/>
* 6.8&nbsp;Mbit/s [[YouTube]] 1080p60 (60 [[Frame rate|FPS]]) videos (using H.264)<ref name="youtube"/>
* 9.8&nbsp;Mbit/s max{{snd}} [[DVD]] (using [[MPEG2]] compression)<ref>{{cite web|url=http://dvd.sourceforge.net/dvdinfo/dvdmpeg.html |title= DVD-MPEG differences | publisher = Sourceforge |access-date=11 July 2011}}</ref>
* 8 to 15&nbsp;Mbit/s typ{{snd}} [[High-definition television|HDTV]] quality (with bit-rate reduction from MPEG-4 AVC compression)
* 19&nbsp;Mbit/s approximate{{snd}} [[HDV]] 720p (using MPEG2 compression)<ref name="hdv-info.org">{{Citation | url = http://www.hdv-info.org/HDVSpecifications.pdf | archive-url = https://web.archive.org/web/20070108204541/http://www.hdv-info.org/HDVSpecifications.pdf | url-status = dead | archive-date = 2007-01-08 | title = HDV Specifications | publisher = HDV Information }}.</ref>
* 24&nbsp;Mbit/s max{{snd}} [[AVCHD]] (using [[H.264/MPEG-4 AVC|MPEG4 AVC]] compression)<ref>{{cite web|url=http://www.avchd-info.org/format/ |title=Avchd Information | publisher = AVCHD Info |access-date=11 July 2011}}</ref>
* 25&nbsp;Mbit/s approximate{{snd}} [[HDV]] 1080i (using MPEG2 compression)<ref name="hdv-info.org"/>
* 29.4&nbsp;Mbit/s max{{snd}} [[HD DVD]]
* 40&nbsp;Mbit/s max{{snd}} [[1080p]] [[Blu-ray Disc]] (using MPEG2, MPEG4 AVC or [[VC-1]] compression)<ref>{{Citation | type = white paper | title = Blu-ray Disc Format 2.B Audio Visual Application Format Specifications for BD-ROM Version 2.4 | date = May 2010 | page = 17 | chapter = 3.3 Video Streams | chapter-url = http://www.blu-raydisc.com/assets/Downloadablefile/BD-ROM-AV-WhitePaper_100604%281%29-15916.pdf}}.</ref>
* 250&nbsp;Mbit/s max{{snd}} [[Digital Cinema Package|DCP]] (using JPEG 2000 compression)
* 1.4&nbsp;Gbit/s{{snd}} 10-bit [[Chroma subsampling|4:4:4]] uncompressed 1080p at 24&nbsp;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 [[Mu-law algorithm|μlaw]] or [[A-law algorithm|A-law]] [[companding]] (pulse code modulation) yield 64&nbsp;kbit/s.