Codecs: Difference between revisions

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[[Category:English pages]]
[[Category:IP telefoni]]
[[Category:Software development]]
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==General==
==General==
* [http://en.wikipedia.org/wiki/List_of_codecs List of codecs - Wikipedia, the free encyclopedia]
* [http://en.wikipedia.org/wiki/List_of_codecs List of codecs - Wikipedia, the free encyclopedia]
* [http://www.intel.com/cd/software/products/asmo-na/eng/perflib/ipp/302910.htm Intel® Integrated Performance Primitives]
* [http://softwarecommunity.intel.com/articles/eng/2649.htm Intel® IPP: Implementing Wideband Codec VoIP Solutions (including sample code)]
==Audio codecs==
==Audio codecs==
* [http://www.itu.int/net/itu-t/sigdb/speaudio/Gseries.htm ITU Codecs and sourcecode]
* [http://www.itu.int/rec/T-REC-G.711.1-200803-I/en Recommendation G.711.1 (03/08) + sourcecode]
* [http://www.readytechnology.co.uk/open/ipp-codecs-g729-g723.1/ Download Open Source G.729 (g729) and G.723.1 (g723) diff codec_g729 codec_g729a codec_g723 for Asterisk Linux]
* [http://www.readytechnology.co.uk/open/ipp-codecs-g729-g723.1/ Download Open Source G.729 (g729) and G.723.1 (g723) diff codec_g729 codec_g729a codec_g723 for Asterisk Linux]
* [http://www.voip-info.org/wiki-ITU+G.729 ITU G.729 - voip-info.org]
* [http://www.voip-info.org/wiki-ITU+G.729 ITU G.729 - voip-info.org]
* [http://www.brothersoft.com/internet/communication/g729_acm_codec_diver_50316.html Free G729 Acm Codec Diver - Plugin codec for RTC Sip softphone]
* [http://www.brothersoft.com/internet/communication/g729_acm_codec_diver_50316.html Free G729 Acm Codec Diver - Plugin codec for RTC Sip softphone]
* [http://www.itu.int/rec/T-REC-G.729/e G.729 : Coding of speech at 8 kbit/s using conjugate-structure algebraic-code-excited linear prediction (CS-ACELP)]
* [http://www.itu.int/rec/T-REC-G.729/e G.729 : Coding of speech at 8 kbit/s using conjugate-structure algebraic-code-excited linear prediction (CS-ACELP)]
* [http://en.wikipedia.org/wiki/List_of_codecs List of codecs - Wikipedia]
* [http://en.wikipedia.org/wiki/G.711 G.711 - Wikikpedia]
* [http://www.ietf.org/internet-drafts/draft-ietf-avt-rtp-g711wb-03.txt  RTP Payload Format for ITU-T Recommendation G.711.1 draft-ietf-avt-rtp-g711wb-03]
==Documents from ITU==
* [http://www.itu.int/rec/T-REC-G.711/e 3 documents G.711 : Pulse code modulation (PCM) of voice frequencies]
* [http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-G.711-198811-I!!PDF-E&type=items ITU-T Recommendation G.711] - (STD.ITU-T RECMN G.711-ENGL 1989)
5 Relationship between the encoding laws and the audio level
The relationship between the encoding laws of Tables 1/G.711 and 2/G.711 and the audio signal level is
defined as follows:
A sine-wave signal of 1 kHz at a nominal level of 0 dBm0 should be present at any voice frequency output of
the PCM multiplex when the periodic sequence of character signals of Table 5/G.711 for the A-law and of
Table 6/G.711 for the m-law is applied to the decoder input.
The resulting theoretical load capacity (Tmax) is +3.14 dBm0 for the A-law, and +3.17 dBm0 for the m-law.
Note - The use of another digital periodic sequence representing a nominal reference frequency of 1020 Hz at
a nominal level of -10 dBm0 (preferred value, see Recommendation O.6) or 0 dBm0 is acceptable, provided that the
theoretical accuracy of that sequence does not differ by more than ± 0.03 dB from a level of -10 dBm0 or 0 dBm0
respectively. In accordance with Recommendation O.6, the specified frequency tolerance should be 1020 Hz + 2 Hz,
-7 Hz.
If a sequence representing -10 dBm0 is used, the nominal value at the voice frequency outputs should be
-10 dBm0.
* [http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-G.711-199909-I!AppI!PDF-E&type=items A high quality low-complexity algorithm for packet loss concealment with G.711]
* [http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-G.711-200002-I!AppII!PDF-E&type=items A comfort noise payload definition for ITU-T G.711 use in packet-based multimedia communication systems]
==Links about Paket sizes and framrates==
Søg f.exk på: g.711 20ms
eller: Packetization g.711 160 80
eller: g711 framerate
eller: itu g.711 frame size
* [http://www.informit.com/articles/article.aspx?p=357102 InformIT: Quality of Service Design Overview > QoS Requirements of VoIP]
* [http://wiki.forum.nokia.com/index.php/KIS000796_-_Frame_length_variation_for_G.711_encoder KIS000796 - Frame length variation for G.711 encoder - Forum Nokia Wiki]
* [http://www.newport-networks.com/cust-docs/52-VoIP-Bandwidth.pdf Newport Networks VoIP Bandwidth Calculation]
* [http://www.tijdhof.com/technotes/tech_faq_codec.pdf GRANDSTREAM NETWORKS FAQ – CODEC]
* [http://www.cisco.com/warp/public/788/pkt-voice-general/bwidth_consume.html Cisco - Voice Over IP - Per Call Bandwidth Consumption]
* [http://msdn.microsoft.com/en-us/library/bb821744.aspx Standards and Drafts for RTC]
* [http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=869713&SiteID=1 Recording and Playing back streaming sound in C# on Motorola Q Smartphone]
* [http://msdn.microsoft.com/en-us/library/ms811371.aspx BufferPositionNotify Structure (Microsoft.DirectX.DirectSound)]
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Latest revision as of 10:46, 3 March 2010

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General

Audio codecs


Documents from ITU

5 Relationship between the encoding laws and the audio level The relationship between the encoding laws of Tables 1/G.711 and 2/G.711 and the audio signal level is defined as follows: A sine-wave signal of 1 kHz at a nominal level of 0 dBm0 should be present at any voice frequency output of the PCM multiplex when the periodic sequence of character signals of Table 5/G.711 for the A-law and of Table 6/G.711 for the m-law is applied to the decoder input. The resulting theoretical load capacity (Tmax) is +3.14 dBm0 for the A-law, and +3.17 dBm0 for the m-law. Note - The use of another digital periodic sequence representing a nominal reference frequency of 1020 Hz at a nominal level of -10 dBm0 (preferred value, see Recommendation O.6) or 0 dBm0 is acceptable, provided that the theoretical accuracy of that sequence does not differ by more than ± 0.03 dB from a level of -10 dBm0 or 0 dBm0 respectively. In accordance with Recommendation O.6, the specified frequency tolerance should be 1020 Hz + 2 Hz, -7 Hz. If a sequence representing -10 dBm0 is used, the nominal value at the voice frequency outputs should be -10 dBm0.

Links about Paket sizes and framrates

Søg f.exk på: g.711 20ms eller: Packetization g.711 160 80 eller: g711 framerate eller: itu g.711 frame size

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