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Adaptive Multi-Rate audio codec
open-in-new
<h2 id="usage">Usage</h2> <p>The frames contain 160 samples and are 20 milliseconds long.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> AMR uses various techniques, such as <a href="/facts/Algebraic_code-excited_linear_prediction/zGb0XLT2">ACELP</a>, <a href="/facts/Discontinuous_transmission/boTbwXJK">DTX</a>, <a href="/facts/Voice_activity_detection/qbCG12fE">VAD</a> and <a href="/facts/Comfort_noise/3IvEmfKA">CNG</a>. The usage of AMR requires optimized link adaptation that selects the best codec mode to meet the local radio channel and capacity requirements. If the radio conditions are bad, <a href="/facts/Source_coding/gMFuY4FT">source coding</a> is reduced and <a href="/facts/Channel_coding/cLUTUJrA">channel coding</a> is increased. This improves the quality and robustness of the network connection while sacrificing some voice clarity. In the particular case of AMR this improvement is somewhere around S/N = 4–6 dB for usable communication. The new intelligent system allows the network operator to prioritize capacity or quality per base station. </p><p>There are a total of 14 modes of the AMR codec, eight are available in a <a href="/facts/Full_Rate/WFfuQf2C">full rate channel (FR)</a> and six on a <a href="/facts/Half_Rate/w2GpD2Gr">half rate channel (HR)</a>. </p> <table><tbody><tr><th>Mode</th><th>Bitrate (kbit/s)</th><th>Channel</th><th>Compatible with</th></tr><tr><td>AMR_12.20</td><td>12.20</td><td>FR</td><td><a href="/facts/Enhanced_full_rate/xwAdEFmy">ETSI GSM enhanced full rate</a></td></tr><tr><td>AMR_10.20</td><td>10.20</td><td>FR</td><td></td></tr><tr><td>AMR_7.95</td><td>7.95</td><td>FR/HR</td><td></td></tr><tr><td>AMR_7.40</td><td>7.40</td><td>FR/HR</td><td><a href="/facts/IS-641/lmLWsLhb">TIA/EIA IS-641 TDMA enhanced full rate</a></td></tr><tr><td>AMR_6.70</td><td>6.70</td><td>FR/HR</td><td><a href="/facts/PDC-EFR/VhtdLdEP">ARIB 6.7 kbit/s enhanced full rate</a></td></tr><tr><td>AMR_5.90</td><td>5.90</td><td>FR/HR</td><td></td></tr><tr><td>AMR_5.15</td><td>5.15</td><td>FR/HR</td><td></td></tr><tr><td>AMR_4.75</td><td>4.75</td><td>FR/HR</td><td></td></tr><tr><td>AMR_SID</td><td>1.80</td><td>FR/HR</td><td></td></tr></tbody></table> <h2 id="features">Features</h2> <ul><li>Sampling frequency 8 kHz/13-bit (160 samples for 20 ms frames), filtered to 200–3400 Hz.</li> <li>The AMR codec uses eight source codecs with bit-rates of 12.2, 10.2, 7.95, 7.40, 6.70, 5.90, 5.15 and 4.75 kbit/s.</li> <li>Generates frame length of 95, 103, 118, 134, 148, 159, 204, or 244 bits for AMR FR bit rates 4.75, 5.15, 5.90, 6.70, 7.40, 7.95, 10.2, or 12.2 kbit/s, respectively. AMR HR frame lengths are different.</li> <li>AMR utilizes <a href="/facts/Discontinuous_transmission/boTbwXJK">discontinuous transmission</a> (DTX), with <a href="/facts/Voice_activity_detection/qbCG12fE">voice activity detection</a> (VAD) and <a href="/facts/Comfort_noise/3IvEmfKA">comfort noise generation</a> (CNG) to reduce bandwidth usage during silence periods</li> <li>Algorithmic delay is 20 ms per frame. For bit-rates of 12.2, there is no "algorithm" look-ahead delay. For other rates, look-ahead delay is 5 ms. Note that there is 5 ms "dummy" look-ahead delay, to allow seamless frame-wise mode switching with the rest of rates.</li> <li>AMR is a hybrid speech coder, and as such transmits both speech parameters and a waveform signal <ul><li><a href="/facts/Linear_predictive_coding/2Bl1xdSN">Linear predictive coding</a> (LPC) is used to synthesize the speech from a residual waveform. The LPC parameters are encoded as <a href="/facts/Line_spectral_pairs/IG1DqDzX">line spectral pairs</a> (LSP).</li> <li>The residual waveform is coded using <a href="/facts/Algebraic_code-excited_linear_prediction/zGb0XLT2">algebraic code-excited linear prediction</a> (ACELP).</li></ul></li> <li>The complexity of the algorithm is rated at 5, using a relative scale where <a href="/facts/G.711/kopBvF25">G.711</a> is 1 and <a href="/facts/G.729a/BB4JexQf">G.729a</a> is 15.</li> <li><a href="/facts/PSQM/YFSPPmP0">PSQM</a> testing under ideal conditions yields <a href="/facts/Mean_opinion_score/EpY5TsQM">mean opinion scores</a> of 4.14 for AMR (12.2 kbit/s), compared to 4.45 for <a href="/facts/G.711/kopBvF25">G.711</a> (μ-law)</li> <li>PSQM testing under network stress yields <a href="/facts/Mean_opinion_score/EpY5TsQM">mean opinion scores</a> of 3.79 for AMR (12.2 kbit/s), compared to 4.13 for <a href="/facts/G.711/kopBvF25">G.711</a> (μ-law)</li></ul> <h2 id="licensing-and-patent-issues">Licensing and patent issues</h2> <p>AMR codecs incorporate several <a href="/facts/Patent/LjT2bG3A">patents</a> of <a href="/facts/Nokia/bCleFoF4">Nokia</a>, <a href="/facts/Ericsson/yJ4oMMp7">Ericsson</a>, <a href="/facts/Nippon_Telegraph_and_Telephone/a3gI457X">NTT</a> and VoiceAge,<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a><a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> the last one being the <i>License Administrator</i> for the AMR <a href="/facts/Patent_pool/t1PErIg3">patent pools</a>. VoiceAge also accepts submission of patents for determination of their possible essentiality to these standards.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a><a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p><p>The initial fee for professional content creation tools and "real-time channel" products is US$6,500.[<i>when?</i>] The minimum annual royalty is $10,000, which, in the first year, excludes the initial fee. Per-channel license fees fall from $0.99 to $0.50 with volume, up to a maximum of $2 million annually.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a><a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p><p>In the category of personal computer products, e.g., media players, the AMR decoder is licensed for free. The license fee for a sold encoder falls from $0.40 to $0.30 with volume, up to a maximum of $300,000 annually. The minimum annual royalty is not applied to licensed products that fall under the category of personal computer products and use only the free decoder.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a><a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> </p><p>More information: </p> <ul><li><a href="http://www.voiceage.com/licensing.php">VoiceAge licensing information</a>, including pricing to license the AMR codecs</li> <li><a href="https://web.archive.org/web/20070630180010/http://www.3gpp.org/legal/legal.htm">3GPP legal issues</a></li> <li><a href="https://web.archive.org/web/20070630180057/http://www.3gpp.org/faq/faq_2005_2.htm#A3.1">The 3G Patent Platform and its licensing policy</a></li> <li><a href="http://www.penguin.cz/~utx/amr">AMR Codecs as Shared Libraries</a> — legal notices for usage of amrnb and amrwb libraries based on the reference implementation</li></ul> <h2 id="software-support">Software support</h2> <ul><li>3GPP TS 26.073 – AMR speech Codec (C source code) – reference implementation<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a></li> <li><a href="/facts/Audacity_(audio_editor)/QadSg3NH">Audacity</a> (beta version 1.3) via the FFmpeg integration libraries<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> (both input and output format)</li> <li><a href="/facts/FFmpeg/85yf3kHI">FFmpeg</a> with OpenCORE AMR libraries<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a></li> <li><a href="/facts/Android_(operating_system)/nNyHb0xz">Android</a><a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> Used for voice recorder.</li> <li><a href="http://www.penguin.cz/~utx/amr">AMR Codecs as Shared Libraries</a> – amrnb and amrwb libraries development site. These libraries are based on the reference implementation and were created to prevent embedding of possibly patented source code into many open source projects.</li> <li>Open source software to convert the .amr format: <a href="http://sourceforge.net/projects/retrocode/">RetroCode</a>, <a href="http://sourceforge.net/projects/amr2wav/">Amr2Wav</a>, both are in an early developmental stage</li> <li><a href="http://www.amrplayer.com/">AMR Player</a> is freeware to play AMR audio files, and can convert AMR from/to MP3/WAV audio format.</li> <li><a href="https://web.archive.org/web/20120422173730/http://www.developer.nokia.com/info/sw.nokia.com/id/d1c17a7f-1231-4385-8c17-04f28f4f2d8e/Nokia_Multimedia_Converter_2.0.html">Nokia Multimedia Converter 2.0 </a> can convert (create) samples, one can use Nokia's conversion tool to create both .amr and .awb files. It works in Windows 7 as well if the setup is run in XP compatibility mode.</li> <li><a href="/facts/MPlayer/nfyW0yjn">MPlayer</a> (<a href="/facts/SMPlayer/cYpRngCb">SMPlayer</a>, KMPlayer<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a>)</li> <li>Parole Media Player 0.8.1 (in Ubuntu 16.04)</li> <li><a href="/facts/QuickTime/rA3GQp2j">QuickTime</a> Player and multimedia framework</li> <li><a href="/facts/RealPlayer/IjS4t5h8">RealPlayer</a> version 11 and later</li> <li><a href="/facts/VLC_media_player/aNurLBXb">VLC media player</a> version 1.1.0 and later (input format only, not output format)</li> <li><a href="/facts/Ffdshow/H60dzfBG">ffdshow</a></li> <li>Apple <a href="/facts/IPhone/h5WeKRl9">iPhone</a> (can play back AMR files)</li> <li><a href="/facts/IOS/mK5cggH5">iOS</a> & <a href="/facts/MacOS/Y93vVpTm">macOS</a> (iMessage)</li> <li><a href="/facts/BlackBerry/k9LGPyg5">BlackBerry</a> smartphones (used for voice recorder file format, while <a href="/facts/BlackBerry_10/WCev9y98">BlackBerry 10</a> cannot play AMR format)</li> <li><a href="/facts/K-Lite_Codec_Pack/Hf5SCvty">K-Lite Codec Pack</a></li> <li><a href="/facts/Media_Player_Classic_Home_Cinema/pfWnozU6">Media Player Classic Home Cinema, around 1.7.1</a></li> <li><a href="/facts/Foobar2000/Pby5dtdw">foobar2000</a> with the component <a href="https://github.com/unjello/foo_input_amr/">foo_input_amr</a></li></ul> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Adaptive_Multi-Rate_Wideband/J70f7LGx">Adaptive Multi-Rate Wideband</a> (AMR-WB)</li> <li><a href="/facts/Extended_Adaptive_Multi-Rate_%25E2%2580%2593_Wideband/TH8Rxo7G">Extended Adaptive Multi-Rate – Wideband</a> (AMR-WB+)</li> <li><a href="/facts/Half_Rate/w2GpD2Gr">Half Rate</a></li> <li><a href="/facts/Full_Rate/WFfuQf2C">Full Rate</a></li> <li><a href="/facts/Enhanced_Full_Rate/xwAdEFmy">Enhanced Full Rate</a> (EFR)</li> <li><a href="/facts/Sampling_rate/xxck7aLN">Sampling rate</a></li> <li><a href="/facts/IS-641/lmLWsLhb">IS-641</a></li> <li><a href="/facts/3GP/EYCqToLu">3GP</a></li> <li><a href="/facts/Comparison_of_audio_coding_formats/vn4Ym1dR">Comparison of audio coding formats</a></li> <li><a href="/facts/RTP_audio_video_profile/RsPjoweL">RTP audio video profile</a></li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="http://www.3gpp.org/ftp/Specs/html-info/26090.htm">3GPP TS 26.090 – Mandatory Speech Codec speech processing functions; Adaptive Multi-Rate (AMR) speech codec; Transcoding functions</a></li> <li><a href="http://www.3gpp.org/ftp/Specs/html-info/26071.htm">3GPP TS 26.071 – Mandatory Speech Codec speech processing functions; AMR Speech Codec; General Description</a></li> <li><a href="http://www.3gpp.org/ftp/Specs/html-info/26-series.htm">3GPP codecs specifications; 3G and beyond / GSM, 26 series</a></li> <li>RFC <a href="https://www.rfc-editor.org/rfc/rfc4867">4867</a> – RTP Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs</li> <li>RFC <a href="https://www.rfc-editor.org/rfc/rfc4281">4281</a> – The Codecs Parameter for "Bucket" Media Types</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"What's toll-quality voice?". ITworld. 13 December 2000. Retrieved 26 July 2019. <a href="https://www.itworld.com/article/2783105/what-s-toll-quality-voice-.html" target="_blank">https://www.itworld.com/article/2783105/what-s-toll-quality-voice-.html</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>RFC 4867 - RTP Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs Page 35 <a href="http://tools.ietf.org/html/rfc4867#page-5" target="_blank">http://tools.ietf.org/html/rfc4867#page-5</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>"Sorting Through GSM Codecs: A Tutorial". 11 July 2003. <a href="http://www.eetimes.com/electronics-news/4139026/Sorting-Through-GSM-Codecs-A-Tutorial" target="_blank">http://www.eetimes.com/electronics-news/4139026/Sorting-Through-GSM-Codecs-A-Tutorial</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>RFC 4867 - RTP Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs Page 35 <a href="http://tools.ietf.org/html/rfc4867#page-35" target="_blank">http://tools.ietf.org/html/rfc4867#page-35</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>"3GPP TS 26.090 - Mandatory Speech Codec speech processing functions; Adaptive Multi-Rate (AMR) speech codec; Transcoding functions". 3GPP. Retrieved 2010-07-21. <a href="http://www.3gpp.org/ftp/Specs/html-info/26090.htm" target="_blank">http://www.3gpp.org/ftp/Specs/html-info/26090.htm</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>VoiceAge Corporation (2007-10-14). "AMR Licensing Terms". VoiceAge Corporation. Archived from the original on 2007-10-14. Retrieved 2009-09-12. <a href="https://web.archive.org/web/20071014162046/http://www.voiceage.com/amr_licterms.php" target="_blank">https://web.archive.org/web/20071014162046/http://www.voiceage.com/amr_licterms.php</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>VoiceAge Corporation (June 2007). "AMR Licensing Terms". VoiceAge Corporation. Archived from the original on 2007-10-14. Retrieved 2009-09-12. <a href="https://web.archive.org/web/20071014162046/http://www.voiceage.com/amr_licterms.php" target="_blank">https://web.archive.org/web/20071014162046/http://www.voiceage.com/amr_licterms.php</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>VoiceAge Corporation. "Licensing - Patent Calls". VoiceAge Corporation. Archived from the original on 2007-10-14. Retrieved 2009-09-12. <a href="https://web.archive.org/web/20071014161420/http://www.voiceage.com/licpatentcalls.php" target="_blank">https://web.archive.org/web/20071014161420/http://www.voiceage.com/licpatentcalls.php</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>VoiceAge Corporation (2007-10-14). "Licensing - Patent Calls". Archived from the original on 2007-10-14. Retrieved 2009-09-12. <a href="https://web.archive.org/web/20071014161420/http://www.voiceage.com/licpatentcalls.php" target="_blank">https://web.archive.org/web/20071014161420/http://www.voiceage.com/licpatentcalls.php</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>VoiceAge Corporation (2007-10-14). "AMR Licensing Terms". VoiceAge Corporation. Archived from the original on 2007-10-14. Retrieved 2009-09-12. <a href="https://web.archive.org/web/20071014162046/http://www.voiceage.com/amr_licterms.php" target="_blank">https://web.archive.org/web/20071014162046/http://www.voiceage.com/amr_licterms.php</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>VoiceAge Corporation (June 2007). "AMR Licensing Terms". VoiceAge Corporation. Archived from the original on 2007-10-14. Retrieved 2009-09-12. <a href="https://web.archive.org/web/20071014162046/http://www.voiceage.com/amr_licterms.php" target="_blank">https://web.archive.org/web/20071014162046/http://www.voiceage.com/amr_licterms.php</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>VoiceAge Corporation (2007-10-14). "AMR Licensing Terms". VoiceAge Corporation. Archived from the original on 2007-10-14. Retrieved 2009-09-12. <a href="https://web.archive.org/web/20071014162046/http://www.voiceage.com/amr_licterms.php" target="_blank">https://web.archive.org/web/20071014162046/http://www.voiceage.com/amr_licterms.php</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>VoiceAge Corporation (June 2007). "AMR Licensing Terms". VoiceAge Corporation. Archived from the original on 2007-10-14. Retrieved 2009-09-12. <a href="https://web.archive.org/web/20071014162046/http://www.voiceage.com/amr_licterms.php" target="_blank">https://web.archive.org/web/20071014162046/http://www.voiceage.com/amr_licterms.php</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>3GPP (2008-12-11) 3GPP TS 26.073 - AMR speech Codec, Retrieved 2009-09-08 <a href="http://www.3gpp.org/ftp/Specs/archive/26_series/26.073/26073-800.zip" target="_blank">http://www.3gpp.org/ftp/Specs/archive/26_series/26.073/26073-800.zip</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Retrieved on 2010-02-28 <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>FFmpeg General Documentation - AMR external library, Retrieved on 2009-07-08 <a href="http://www.ffmpeg.org/general.html" target="_blank">http://www.ffmpeg.org/general.html</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Android AMR codecs, Retrieved on 2009-07-08 Archived February 18, 2009, at the Wayback Machine <a href="http://android.git.kernel.org/?p=platform/external/opencore.git;a=tree;f=codecs_v2/audio/gsm_amr;hb=HEAD" target="_blank">http://android.git.kernel.org/?p=platform/external/opencore.git;a=tree;f=codecs_v2/audio/gsm_amr;hb=HEAD</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>KMPlayer Internal Audio Decoder Preferences Archived 2014-10-22 at the Wayback Machine, Retrieved 2014-10-22 <a href="http://www.softadept.com/read/kmplayer-internal-audio-decoder-preferences-overview/" target="_blank">http://www.softadept.com/read/kmplayer-internal-audio-decoder-preferences-overview/</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> </ol>