Real Lossless Codec: Difference between revisions

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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 08:35, 10 March 2012

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
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