QCELP - Revision history

Vitor: Remove Category:Undiscovered Audio Codecs

2009-09-03T04:50:45Z

Remove Category:Undiscovered Audio Codecs

← Older revision		Revision as of 21:50, 2 September 2009
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	Qualcomm shared its source for QCELP during the development of the codec. Sometime along the development [[Apple]] licenced the codec for [[Apple QuickTime Player\|QuickTime]]. The code doesn't match the binary completely but will help an eventual RE effort. Qualcomm also supply a SDK. http://www.cdmatech.com/products/purevoice_download.jsp This is for the standard QCELP and not for the QCELP found in [[MOV]] files.		Qualcomm shared its source for QCELP during the development of the codec. Sometime along the development [[Apple]] licenced the codec for [[Apple QuickTime Player\|QuickTime]]. The code doesn't match the binary completely but will help an eventual RE effort. Qualcomm also supply a SDK. http://www.cdmatech.com/products/purevoice_download.jsp This is for the standard QCELP and not for the QCELP found in [[MOV]] files.

	~~[[Category:Undiscovered Audio Codecs]]~~
	[[Category:Audio Codecs]]		[[Category:Audio Codecs]]
	[[Category:Vocoders]]		[[Category:Vocoders]]

DonDiego: saner wikification

2007-05-14T16:19:55Z

saner wikification

← Older revision		Revision as of 09:19, 14 May 2007
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	'''QCELP''', also known as '''[[Qualcomm PureVoice]]''', is a [[~~speech codec~~]] developed in 1994 to increase the speech quality of the [[IS-96A]] codec used earlier in ~~[[Code division multiple access\|~~CDMA]] networks. It was replaced later with [[Enhanced Variable Rate Codec\|EVRC]] since it provides better speech quality with fewer bits. There are two versions available: ''QCELP8'' and ''QCELP13'' and they use 8 and 13 Kbit/s respectively.		'''QCELP''', also known as '''Qualcomm PureVoice''', is a [[vocoder]] developed in 1994 to increase the speech quality of the [[IS-96A]] codec used earlier in CDMA networks. It was replaced later with [[Enhanced Variable Rate Codec\|EVRC]] since it provides better speech quality with fewer bits. There are two versions available: ''QCELP8'' and ''QCELP13'' and they use 8 and 13 Kbit/s respectively.

	Adopted in CDMA system is a QCELP vocoder with variable rates, which is actually a device converting a sound signal into the signal which can be transmitted in a circuit. The method adopted generally in a wire communication system is to first sample (8,000 sample values generated per second) a voice signal with an 8kHz signal and then implement 8-bit [[quantization (sound processing)\|quantization]] coding for each sample value. Therefore, each voice channel in a wired system has the rate of 64K. However, because the air resource in a wireless system is very precious, a more effective coding mode is needed to use a rate as low as possible in the case where voice quality is guaranteed. A QCELP vocoder with variable rates is such a device. The main principles of it are to extract some voice feature parameters when a person speaks and transmit these feature parameters to the peer party. Then, the peer party will recover the voice with these parameters based on the promise between the two parties. Thus, a far lower rate is needed.		Adopted in CDMA system is a QCELP vocoder with variable rates, which is actually a device converting a sound signal into the signal which can be transmitted in a circuit. The method adopted generally in a wire communication system is to first sample (8,000 sample values generated per second) a voice signal with an 8kHz signal and then implement 8-bit [[quantization (sound processing)\|quantization]] coding for each sample value. Therefore, each voice channel in a wired system has the rate of 64K. However, because the air resource in a wireless system is very precious, a more effective coding mode is needed to use a rate as low as possible in the case where voice quality is guaranteed. A QCELP vocoder with variable rates is such a device. The main principles of it are to extract some voice feature parameters when a person speaks and transmit these feature parameters to the peer party. Then, the peer party will recover the voice with these parameters based on the promise between the two parties. Thus, a far lower rate is needed.
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	The codes transmitted from the transmit end to the receive end and describing voice feature parameters vary with the rhythm or loudness of a speech. These variable rates mean that a vocoder can change its own code rates based on the loudness or rhythm of a speech to further reduce a code rate. Thus, a code with a higher rate will be adopted when there is a high-pitched voice while a code with a lower rate will be adopted when there is a low-pitched voice. In a silent period (when a person makes no sound during a speech), the lowest code rate will be adopted. Thus, a code rate can be decreased to reduce the interference with other users.		The codes transmitted from the transmit end to the receive end and describing voice feature parameters vary with the rhythm or loudness of a speech. These variable rates mean that a vocoder can change its own code rates based on the loudness or rhythm of a speech to further reduce a code rate. Thus, a code with a higher rate will be adopted when there is a high-pitched voice while a code with a lower rate will be adopted when there is a low-pitched voice. In a silent period (when a person makes no sound during a speech), the lowest code rate will be adopted. Thus, a code rate can be decreased to reduce the interference with other users.

	[[Qualcomm]] shared its source for ~~[[Qualcomm Voice Codec\|~~QCELP]] during the development of the codec. Sometime along the development [[Apple]] licenced the codec for [[Apple QuickTime Player\|QuickTime]]. The code doesn't match the binary completely but will help an eventual RE effort. Qualcomm also supply a SDK. http://www.cdmatech.com/products/purevoice_download.jsp This is for the standard QCELP and not for the QCELP found in ~~mov~~ files.		Qualcomm shared its source for QCELP during the development of the codec. Sometime along the development [[Apple]] licenced the codec for [[Apple QuickTime Player\|QuickTime]]. The code doesn't match the binary completely but will help an eventual RE effort. Qualcomm also supply a SDK. http://www.cdmatech.com/products/purevoice_download.jsp This is for the standard QCELP and not for the QCELP found in [[MOV]] files.

	[[Category:Undiscovered Audio Codecs]]		[[Category:Undiscovered Audio Codecs]]
	[[Category:Audio Codecs]]		[[Category:Audio Codecs]]
	[[Category:Vocoders]]		[[Category:Vocoders]]

Crybaby: added more qcelp info

2007-05-10T06:29:18Z

added more qcelp info

@@ Line 2: / Line 2: @@
 * Specification: QCELP decoder [http://www.3gpp2.org/Public_html/specs/alltsgscfm.cfm spec] is c.s0020 and source is c.r0020
-* Sample files: http://samples.mplayerhq.hu/A-codecs/qclp/
 '''QCELP''', also known as '''[[Qualcomm PureVoice]]''', is a [[speech codec]] developed in 1994 to increase the speech quality of the [[IS-96A]] codec used earlier in [[Code division multiple access|CDMA]] networks. It was replaced later with [[Enhanced Variable Rate Codec|EVRC]] since it provides better speech quality with fewer bits. There are two versions available:  ''QCELP8'' and ''QCELP13'' and they use 8 and 13 Kbit/s respectively.
@@ Line 13: / Line 23: @@
 [[Qualcomm]] shared its source for [[Qualcomm Voice Codec|QCELP]] during the development of the codec. Sometime along the development [[Apple]] licenced the codec for [[Apple QuickTime Player|QuickTime]]. The code doesn't match the binary completely but will help an eventual RE effort. Qualcomm also supply a SDK. http://www.cdmatech.com/products/purevoice_download.jsp This is for the standard QCELP and not for the QCELP found in mov files.

Crybaby: /* QCELP */

2007-05-10T06:27:03Z

QCELP

← Older revision		Revision as of 23:27, 9 May 2007
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	The codes transmitted from the transmit end to the receive end and describing voice feature parameters vary with the rhythm or loudness of a speech. These variable rates mean that a vocoder can change its own code rates based on the loudness or rhythm of a speech to further reduce a code rate. Thus, a code with a higher rate will be adopted when there is a high-pitched voice while a code with a lower rate will be adopted when there is a low-pitched voice. In a silent period (when a person makes no sound during a speech), the lowest code rate will be adopted. Thus, a code rate can be decreased to reduce the interference with other users.		The codes transmitted from the transmit end to the receive end and describing voice feature parameters vary with the rhythm or loudness of a speech. These variable rates mean that a vocoder can change its own code rates based on the loudness or rhythm of a speech to further reduce a code rate. Thus, a code with a higher rate will be adopted when there is a high-pitched voice while a code with a lower rate will be adopted when there is a low-pitched voice. In a silent period (when a person makes no sound during a speech), the lowest code rate will be adopted. Thus, a code rate can be decreased to reduce the interference with other users.

			[[Qualcomm]] shared its source for [[Qualcomm Voice Codec\|QCELP]] during the development of the codec. Sometime along the development [[Apple]] licenced the codec for [[Apple QuickTime Player\|QuickTime]]. The code doesn't match the binary completely but will help an eventual RE effort. Qualcomm also supply a SDK. http://www.cdmatech.com/products/purevoice_download.jsp This is for the standard QCELP and not for the QCELP found in mov files.

Crybaby: initial version adapted from wikipedia entry

2007-05-10T06:24:41Z

initial version adapted from wikipedia entry

New page

==== QCELP ====

* Specification: QCELP decoder [http://www.3gpp2.org/Public_html/specs/alltsgscfm.cfm spec] is c.s0020 and source is c.r0020
* Sample files: http://samples.mplayerhq.hu/A-codecs/qclp/

'''QCELP''', also known as '''[[Qualcomm PureVoice]]''', is a [[speech codec]] developed in 1994 to increase the speech quality of the [[IS-96A]] codec used earlier in [[Code division multiple access|CDMA]] networks. It was replaced later with [[Enhanced Variable Rate Codec|EVRC]] since it provides better speech quality with fewer bits. There are two versions available: ''QCELP8'' and ''QCELP13'' and they use 8 and 13 Kbit/s respectively.

Adopted in CDMA system is a QCELP vocoder with variable rates, which is actually a device converting a sound signal into the signal which can be transmitted in a circuit. The method adopted generally in a wire communication system is to first sample (8,000 sample values generated per second) a voice signal with an 8kHz signal and then implement 8-bit [[quantization (sound processing)|quantization]] coding for each sample value. Therefore, each voice channel in a wired system has the rate of 64K. However, because the air resource in a wireless system is very precious, a more effective coding mode is needed to use a rate as low as possible in the case where voice quality is guaranteed. A QCELP vocoder with variable rates is such a device. The main principles of it are to extract some voice feature parameters when a person speaks and transmit these feature parameters to the peer party. Then, the peer party will recover the voice with these parameters based on the promise between the two parties. Thus, a far lower rate is needed.

Let's give an example. The information of a triangle can be transmitted from one place to another in two ways: one is to obtain some points by means of sampling and transmit the information of these points to the peer party. The two parties connect these points to obtain a triangle. The other is to transmit the length of a side and the degrees of two angles of this triangle to the peer party, who can likewise recover this triangle based on these pieces of information. Obviously, there is far less information to be transmitted in the second method. What a vocoder does is similar to the latter method, but what a vocoder actually does is more complex than this. But the principles are the same.

The codes transmitted from the transmit end to the receive end and describing voice feature parameters vary with the rhythm or loudness of a speech. These variable rates mean that a vocoder can change its own code rates based on the loudness or rhythm of a speech to further reduce a code rate. Thus, a code with a higher rate will be adopted when there is a high-pitched voice while a code with a lower rate will be adopted when there is a low-pitched voice. In a silent period (when a person makes no sound during a speech), the lowest code rate will be adopted. Thus, a code rate can be decreased to reduce the interference with other users.