Hi folks!
> That said, the notion of managing the different bitrates does present a
> challenge. I therefore suggest any such encoded file have some "magic"
> bytes at the beginning, even if this is something as simple as 0x43 0x32
> ("C2"). I then propose the next byte be the mode ID as defined in
> codec2.h. This would allow c2enc/c2dec to be retrofitted or separate
> tools to be constructed to Do The Right Thing™ based on these.
May I suggest a bitstream header format that encodes all the profile
parameters, so that new profiles can be added without changing the
header format or adding new "magic" numbers for profiles.
73 de txp0wer
>
> If we can agree on these bytes, I'm happy to take a stab at coding this
> up. It doesn't look like it should be too difficult (famous last words!)
>
> 73 de Kevin N8VNR
>
> On 05/22/2017 04:35 PM, Kevin Otte wrote:
> > Or Matroska (.mka):
> > https://matroska.org/technical/specs/index.html
> >
> > On 05/22/2017 02:28 PM, Bruce Perens wrote:
> > > See https://www.xiph.org/ogg/doc/rfc3533.txt . Make it work with the
> > > Ogg Encapsulation Format.
<code language="pseudocode" style="Rust">
// data types:
// u8 == unsigned 8-bit integer
// u16b == unsigned 16-bit integer, big endian
struct Codec2Header{
magic_identification :u24b, // offset 0 bytes
// const 0xC0DEC2 ([0xC0,0xDE,0xC2])
major_version :u8, // offset 3 bytes //
minor_version :u8, // offset 4 bytes //
forward_ec_level :u8, // offset 6 bytes //
flags :u8, // offset 5 bytes // default 0
subframes_per_frame :u8, // offset 7 bytes // 1 to 4
samples_per_subframe :u16b, // offset 8 bytes
samplerate_hz :u16b // offset 10 // default 8000
};
struct Codec2SubframeParameters{ // offset 12
// repeated [subframes_per_frame] times
lsp_bits_per_frame :u8, // offset 12+4*n
pitch_bits_per_frame :u8, // offset 12+4*n+(0..1)
energy_bits_per_frame :u8, // offset 4*n+(0..1)
voicing_bits_per_frame :u8 // offset 4*n+(0..1)
}
match forward_ec_level{
0=>none,
1=>"1200",
2=>"1850",
3=>"2000",
_=>undefined
}
flags:
0x01=NATURAL_BYTE_ORDER // --natural
0x02=ALTERNATE_MODE_1 // "B"
0x04=ALTERNATE_MODE_2 // "C", "D"
0x08=ALTERNATE_MODE_4 // "E" .. "H"
0x10=unused
0x20=unused
0x40=unused
0x80=ALTERNATE_CODEBOOK_1
</code>
example (hex)
# "3200" default profile
# begin Codec2Header
00: C0 DE C2
03: 00 04 # version 0.4
05: 00 # no forward error correction
06: 00 # flags: gray code, no alternate profile, no alternate codebook
07: 02 # 2 subframes per frame
08: 00 a0 # 160 samples per subframe => 320 samples per frame
0a: 1f 40 # 8000 Hz
# end Codec2Header, begin Codec2SubframeParameters
# # begin subframe 0 # if I understand codec2_encode_3200() right
0c: 20 # 32 bits LSP
0d: 00 # 0 bits pitch
0e: 00 # 0 bits energy
0f: 00 # 0 bits voicing
# # end subframe 0, begin subframe 1
10: 12 # 18 bits LSP
11: 07 # 0 bits pitch
12: 05 # 0 bits energy
13: 02 # 0 bits voicing
# # end subframe 1
# end Codec2SubframeParameters, begin data bitstream
------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot
_______________________________________________
Freetel-codec2 mailing list
Freetel-codec2@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/freetel-codec2
