GoToMeeting Codec

Compn — Wed, 08 May 2013 02:01:09 GMT

update samples url due to more samples

Revision as of 02:01, 8 May 2013		Current revision
Line 4:		Line 4:
	** G2M2: http://samples.mplayerhq.hu/V-codecs/G2M2/		** G2M2: http://samples.mplayerhq.hu/V-codecs/G2M2/
	** G2M3: http://samples.mplayerhq.hu/V-codecs/G2M3/		** G2M3: http://samples.mplayerhq.hu/V-codecs/G2M3/
-	** G2M4: http://samples.mplayerhq.hu/V-codecs/G2M4/	+	** G2M4: http://samples.ffmpeg.org/V-codecs/G2M4/

	This is a codec used to save recordings in GoToMeeting. The codec also calls itself GoToWebinar (see [http://www.gotowebinar.com/ http://www.gotowebinar.com/]).		This is a codec used to save recordings in GoToMeeting. The codec also calls itself GoToWebinar (see [http://www.gotowebinar.com/ http://www.gotowebinar.com/]).

Maxpol — Tue, 07 May 2013 08:02:48 GMT

/* ELS values */

Revision as of 08:02, 7 May 2013		Current revision
Line 84:		Line 84:
	==== ELS values ====		==== ELS values ====

-	Unsigned values are coded as a number with all bits set to one and an addition to it:	+	Unsigned values are coded using Exponential Golomb notation:

-	mask = 1;	+	unary prefix + stop bit + remainder, where number of bits in the prefix = number of bits in the remainder
-	val = 0;	+
-		+
-	while (decode_bit()) {	+
-	val += mask;	+
-	mask <<= 1;	+
-	}	+
-	while (mask > 1) {	+
-	mask >>= 1;	+
-	if (decode_bit())	+
-	val += mask;	+
-	}	+

-	E.g. number 5 will be coded as <code>11 0 10</code> (i.e. 3 + stop bit + 2).	+	The unary prefix is coded as n -1 zero bits followed by a one bit. E.g. number 5 will be coded as <code>00 1 10</code>.

-	Signed values use last bit for sign:	+	Here is the decoding algorithm:
		+
		+	count number of bits in the prefix by reading bits from the arithmetic ELS decoder until a "1" is encountered
		+	n = number of zero bits in the prefix, i.e "001" ==> n = 2
		+	read the remainder r as plain binary number of n bits: "10" ==> 2
		+	value = 2<sup>n</sup> - 1 + r = 2<sup>2</sup> - 1 + 2 = 5
		+
		+	Signed values are coded as unsigned ones where the LSB indicates the sign:

	if (val & 1)		if (val & 1)

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