Information on Audio Codecs - Revision history

Gijs: /* Audio codec translations */

2007-02-20T19:45:08Z

Audio codec translations

Gijs: /* Audio codec translations */

2007-02-12T15:18:07Z

Audio codec translations

Gijs at 15:16, 12 February 2007

2007-02-12T15:16:33Z

Gijs: /* Various codecs compared */

2007-02-06T10:48:40Z

Various codecs compared

Gijs: /* Various codecs compared */

2007-02-06T10:46:30Z

Various codecs compared

Rubzzzz: Audio Codecs moved to Information on Audio Codecs

2007-02-06T10:20:58Z

Audio Codecs moved to Information on Audio Codecs

82.73.15.45 at 14:39, 31 January 2007

2007-01-31T14:39:58Z

82.73.15.45 at 14:39, 31 January 2007

2007-01-31T14:39:48Z

Gijs: Added frame-size to the table and some extra codecs.

2007-01-31T00:08:46Z

Added frame-size to the table and some extra codecs.

Gijs at 23:21, 30 January 2007

2007-01-30T23:21:13Z

← Older revision		Revision as of 19:45, 20 February 2007
Line 166:		Line 166:
	512 (1 << 9) (0x200) audio speex (SpeeX)		512 (1 << 9) (0x200) audio speex (SpeeX)
	1024 (1 << 10) (0x400) audio ilbc (iLBC)		1024 (1 << 10) (0x400) audio ilbc (iLBC)
		+
		+	==[[Links#Audio_codecs\|Links]]==

@@ Line 132: / Line 132: @@
 When Asterisk can choose between different codecs (prerecorded samples) and also when conversions between codecs have to be made (e.g. bandwidth=low), Asterisk will choose the best codec out of the conversion-matrix.
-In the Asterisk CLI this machine-specific matrix can be shown:
+In the Asterisk CLI this machine-specific matrix can be shown: (N.B. matrix is taken from a P3 machine)
   asterisk1*CLI> show translation
            Translation times between formats (in milliseconds)

← Older revision		Revision as of 15:16, 12 February 2007
Line 127:		Line 127:

	*Codecs with a frame-size other than 20 ms, appear to work bad with Asterisk. This may have to do with the IAX-protocol.		*Codecs with a frame-size other than 20 ms, appear to work bad with Asterisk. This may have to do with the IAX-protocol.
		+
		+
		+	==Audio codec translations==
		+	When Asterisk can choose between different codecs (prerecorded samples) and also when conversions between codecs have to be made (e.g. bandwidth=low), Asterisk will choose the best codec out of the conversion-matrix.
		+
		+	In the Asterisk CLI this machine-specific matrix can be shown:
		+	asterisk1*CLI> show translation
		+	Translation times between formats (in milliseconds)
		+	Source Format (Rows) Destination Format(Columns)
		+	g723 gsm ulaw alaw g726 adpcm slin lpc10 g729 speex ilbc
		+	g723 - - - - - - - - - - -
		+	gsm - - 3 3 7 3 2 8 - 86 30
		+	ulaw - 7 - 1 6 2 1 7 - 85 29
		+	alaw - 7 1 - 6 2 1 7 - 85 29
		+	g726 - 10 5 5 - 5 4 10 - 88 32
		+	adpcm - 7 2 2 6 - 1 7 - 85 29
		+	slin - 6 1 1 5 1 - 6 - 84 28
		+	lpc10 - 12 7 7 11 7 6 - - 90 34
		+	g729 - - - - - - - - - - -
		+	speex - 12 7 7 11 7 6 12 - - 34
		+	ilbc - 14 9 9 13 9 8 14 - 92 -
		+
		+	The list of available codecs can be made visible like this:
		+	asterisk1*CLI> show audio codecs
		+	Disclaimer: this command is for informational purposes only.
		+	It does not indicate anything about your configuration.
		+	INT BINARY HEX TYPE NAME DESC
		+	--------------------------------------------------------------------------------
		+	1 (1 << 0) (0x1) audio g723 (G.723.1)
		+	2 (1 << 1) (0x2) audio gsm (GSM)
		+	4 (1 << 2) (0x4) audio ulaw (G.711 u-law)
		+	8 (1 << 3) (0x8) audio alaw (G.711 A-law)
		+	16 (1 << 4) (0x10) audio g726 (G.726)
		+	32 (1 << 5) (0x20) audio adpcm (ADPCM)
		+	64 (1 << 6) (0x40) audio slin (16 bit Signed Linear PCM)
		+	128 (1 << 7) (0x80) audio lpc10 (LPC10)
		+	256 (1 << 8) (0x100) audio g729 (G.729A)
		+	512 (1 << 9) (0x200) audio speex (SpeeX)
		+	1024 (1 << 10) (0x400) audio ilbc (iLBC)

@@ Line 114: / Line 114: @@
 |}
-From the maximum voice quality point of view, when enough bandwidth is available, the best quality can be obtained by using the L16 PCM codec. This L16 PCM codec is the same as the G.711 codec, however the L16 PCM codec samples to 16 bits samples instead of the 8 bits samples in the case of the G.711 codec.
+''NEB = Nominal Ethernet Bandwidth (one direction)''
-Codecs with a frame-size other than 20 ms, appear to work bad with Asterisk. This may have to do with the IAX-protocol.
+'''Notes''':

@@ Line 25: / Line 25: @@
 ! Compression method
 ! Transfer rate
 ! Frame size
 |-
@@ Line 30: / Line 31: @@
 |Pulse Code Modulation (PCM)
 |64 Kbps
 |20 ms
 |-
@@ Line 35: / Line 37: @@
 |Adaptive Differential Pulse Code Modulation (ADPCM)
 |16-40 Kbps
+|
 |-
@@ Line 40: / Line 43: @@
 |Low Delay Code Excited Linear Prediction (LD-CELP)
 |16 Kbps
 |0,625ms
 |-
@@ Line 45: / Line 49: @@
 |Conjugate Structure Algebraic Code Excited Linear Prediction (CD-ACELP)
 |8 Kbps
 |10 ms
 |-
 |G.723.1
 |Mulptiple Maximum Likehood Quantization (MPMLQ)
-|6,3 Kbit/s
+|6.3 Kbit/s
-|37,5 ms
+|21.9 Kbps
 |-
 |G.723
 |ACELP
 |5,3 Kbps
+|
 |-
@@ Line 60: / Line 67: @@
 |Global System for Mobile communications
 |13 Kbps
 |20ms
 |-
@@ Line 65: / Line 73: @@
 |Patent-free audio compression
 |2.15-24.6 Kbps
 |20ms
 |-
@@ Line 70: / Line 79: @@
 |Patent-free audio compression
 |4-44.2 Kbps
 |20ms
 |-
@@ Line 75: / Line 85: @@
 |ADPCM
 |32 Kbps
+|
 |-
@@ Line 80: / Line 91: @@
 |Internet Low Bandwidth Codec (free)
 |13,3 Kbps
 |30ms
 |-
@@ Line 85: / Line 97: @@
 |Internet Low Bandwidth Codec (free)
 |15,2 Kbps
 |20ms
 |-
@@ Line 90: / Line 103: @@
 |PCM
 |128 Kbps
+|
 |-
@@ Line 95: / Line 109: @@
 |Enhanced Variable Rate Codec
 |8 Kbps
+|
 |-

← Older revision	Revision as of 10:20, 6 February 2007
(No difference)

← Older revision		Revision as of 14:39, 31 January 2007
Line 5:		Line 5:

	X-lite has various audio codecs implemented. The [http://www.xten.com/index.php?menu=Products&smenu=compare implemented audio codecs] of the X-lite 3.0 version are DVI4, G.711 uLaw/aLaw, GSM, iLBC as (narrow band audio codecs) and BV-32, BV FEC, DVI4, L16 PCM (wide band audio codecs). Eyebeam version 1.5 has a wider range of codecs available.		X-lite has various audio codecs implemented. The [http://www.xten.com/index.php?menu=Products&smenu=compare implemented audio codecs] of the X-lite 3.0 version are DVI4, G.711 uLaw/aLaw, GSM, iLBC as (narrow band audio codecs) and BV-32, BV FEC, DVI4, L16 PCM (wide band audio codecs). Eyebeam version 1.5 has a wider range of codecs available.
		+

	=== G.711A & G.711U ===		=== G.711A & G.711U ===

@@ Line 6: / Line 6: @@
 X-lite has various audio codecs implemented. The [http://www.xten.com/index.php?menu=Products&smenu=compare implemented audio codecs] of the X-lite 3.0 version are DVI4, G.711 uLaw/aLaw, GSM, iLBC as (narrow band audio codecs) and BV-32, BV FEC, DVI4, L16 PCM (wide band audio codecs). Eyebeam version 1.5 has a wider range of codecs available.
-From the [http://www.xten.com/docs/CounterPath_UserGuideXLite-XPRO.pdf  User’s Guide for X-Lite and X-PRO] (p.34) the following can be said:
+<strike>From the [http://www.xten.com/docs/CounterPath_UserGuideXLite-XPRO.pdf  User’s Guide for X-Lite and X-PRO] (p.34) the following can be said:
 "When two VoIP systems are establishing a call, they negotiate an audio compression codec they
@@ Line 13: / Line 13: @@
 quality, etc. During the negotiation, X-Lite/X-PRO offers to the remote system the first audio
 compression codec from the list. If the remote system rejects the audio compression codec, XLite/X-PRO offers the next one from top to bottom until they both accept the audio compression
-codec."
+codec."</strike>