Real Lossless Codec

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	Known decoder support only 1/2 channel 16-bit audio with sampling rate up to 96 kHz.		Known decoder support only 1/2 channel 16-bit audio with sampling rate up to 96 kHz.
		+
		+	== Frame format ==
		+
		+	Data is read MSB.
		+
		+	=== Block header ===
		+
		+	get frame length code
		+	if (stereo)
		+	decoding_mode = get_bits(2) + 1;
		+	else
		+	decoding_mode = 0;
		+
		+	Frame length code:
		+
		+	64 - 11110
		+	128 - 11111
		+	256 - 1110
		+	512 - 110
		+	1024 - 10
		+	2048 - 0
		+
		+	Decoding mode specifies table sets, bits and channel recombining:
		+
		+	{| border="1" cellpadding="5" style="border-collapse: collapse; border-style: dashed; border-color: #2f6fab;"
		+	|- bgcolor="#f0f0f0" |
		+	! Mode !! tableset1 !! bits1 !! tableset2 !! bits2 !! Channel decoupling
		+	|-
		+	| align="center" | 0 || align="center" | 0 || align="center" | 16 || align="center" | n/a || align="center" | n/a || align="center" | mono
		+	|-
		+	| align="center" | 1 || align="center" | 0 || align="center" | 16 || align="center" | 0 || align="center" | 16 || align="center" | L, R
		+	|-
		+	| align="center" | 2 || align="center" | 0 || align="center" | 16 || align="center" | 2 || align="center" | 17 || align="center" | L+R, R
		+	|-
		+	| align="center" | 3 || align="center" | 1 || align="center" | 16 || align="center" | 2 || align="center" | 17 || align="center" | L, R-L
		+	|-
		+	| align="center" | 4 || align="center" | 2 || align="center" | 17 || align="center" | 2 || align="center" | 17 || align="center" | (L+R)/2, (L-R)/2
		+	|}
		+
	[[Category:Undiscovered Audio Codecs]]		[[Category:Undiscovered Audio Codecs]]
	[[Category:Lossless Audio Codecs]]		[[Category:Lossless Audio Codecs]]
	[[Category:Audio Codecs]]		[[Category:Audio Codecs]]

---

Revision as of 15:35, 10 March 2012

• FOURCCs: ralf
• Company: RealNetworks
• Samples: http://samples.mplayerhq.hu/A-codecs/lossless/ (luckynight.rmvb)

This is RealNetworks lossless audio codec.

Audio header in rm files is different from other Real audio codecs; the interface of the binary decoder is also different.

Extradata format

Numbers are stored big-endian.

bytes  0- 3 - codec FOURCC, always "LSD:"
bytes  4- 5 - version
bytes  8- 9 - number of channels
bytes 10-11 - bits per sample
bytes 12-15 - sampling rate
bytes 16-19 - block size in samples?
bytes 20-23 - ignored?

Known decoder support only 1/2 channel 16-bit audio with sampling rate up to 96 kHz.

Frame format

Data is read MSB.

Block header

 get frame length code
 if (stereo)
   decoding_mode = get_bits(2) + 1;
 else
   decoding_mode = 0;

Frame length code:

   64 - 11110
  128 - 11111
  256 - 1110
  512 - 110
 1024 - 10
 2048 - 0

Decoding mode specifies table sets, bits and channel recombining:

Mode	tableset1	bits1	tableset2	bits2	Channel decoupling
0	0	16	n/a	n/a	mono
1	0	16	0	16	L, R
2	0	16	2	17	L+R, R
3	1	16	2	17	L, R-L
4	2	17	2	17	(L+R)/2, (L-R)/2