Created: Feb 27, 2005

The RVF file format (unofficial)

Contents
1. a normal RVF file format
1.1 how did I find out the RVF file format
1.2 to convert from RVF files to MP3 files

2. a special RVF file format
2.1 an older firmware RVF file format
2.2 to convert from older firmware RVF files to MP3 files

1. a normal RVF file format

1.1 how did I find out the RVF file format

This is a sample HEX dump of an HQ mode(16kbps) RVF file.

0000000  a6bc 7d8a 5445 4c2d 114f 554e 5409 0d63
0000020  1c7c 7b77 6610 197b 0c1a 001b 0110 197b
0000040  0c1a 001b 0110 197b 0c1a 001b 0110 197b
0000060  0c1a 001b 0110 197b 0c1a 001b 0110 197b
0000100  0c1a 001b 0110 197b a6bc 7d8a 6f45 4c2d
0000120  114f 554e 5410 197b 0c1a 001b 0110 197b
0000140  0c1a 001b 0110 197b 0c1a 001b 0110 197b
0000160  0c1a 001b 0110 197b 0c1a 001b 0110 197b
0000200  0c1a 001b 0110 197b 0c1a 001b 0110 197b
0000220  a6bc 7d8a 2245 4c2d 114f 554e 5410 197b
0000240  0c1a 001b 0110 197b 0c1a 001b 0110 197b
0000260  0c1a 001b 0110 197b 0c1a 001b 0110 197b
0000300  0c1a 001b 0110 197b 0c1a 001b 0110 197b
0000320  0c1a 001b 0110 197b
0000330

I converted this RVF file to WAV file by TM-Explorer, and converted the WAV file to MP3 file by some freeware. Sizes of the RVF file and the MP3 file were exactly the same.

This is the HEX dump of the converted MP3 file.

0000000  fff3 28c4 0000 0003 4800 0000 0047 4f47
0000020  4f47 4f47 4f47 4f47 4f47 4f47 4f47 4f47
0000040  4f47 4f47 4f47 4f47 4f47 4f47 4f47 4f47
0000060  4f47 4f47 4f47 4f47 4f47 4f47 4f47 4f47
0000100  4f47 4f47 4f47 4f47 fff3 28c4 3b00 0003
0000120  4800 0000 004f 474f 474f 474f 474f 474f
0000140  474f 474f 474f 474f 474f 474f 474f 474f
0000160  474f 474f 474f 474f 474f 474f 474f 474f
0000200  474f 474f 474f 474f 474f 474f 474f 474f
0000220  fff3 28c4 7600 0003 4800 0000 0047 4f47
0000240  4f47 4f47 4f47 4f47 4f47 4f47 4f47 4f47
0000260  4f47 4f47 4f47 4f47 4f47 4f47 4f47 4f47
0000300  4f47 4f47 4f47 4f47 4f47 4f47 4f47 4f47
0000320  4f47 4f47 4f47 4f55
0000330

You can see the MP3 syncwords `fff3 28c4' frequently appear in the MP3 file,
and also you can see the words `a6bc 7d8a' in the RVF file on the same address.
It seems an RVF file is simply encrypted an MP3 file format.

So, I assume RVF files were XOR encrypted MP3 files.
To find out the XOR key, I re-XORed these files.
Finally I found the key. The key is `594f 554e 5445 4c2e'.
In ascii code, it is `YOUNTEL.'.
Yountel Corporation(KOREA) is a manufacture of a 1 chip MP3 encoder/decoder IC.
I guess Radio YourWay / TalkMaster / DDR-4000 has Yountel's IC.

1.2 to convert from RVF files to MP3 files

To convert from RVF files to MP3 files, it's easy.
You simply XOR RVF data with the key `594f 554e 5445 4c2e' continuing from first to the end of the RVF files.

2. a special RVF file format

2.1 older firmware RVF file format

I found some RVF data could not convert the simple XOR method as memtioned above.
Especially an old firmware (I found it firmware version 1.1) and recorded onto an external memory, the RVF file is not so simple.

The first 576 bytes are unknown data.
And the following data are the same as normal RVF (as far as I know).

This is a sample HEX dump of an SHQ mode(32kbps) RVF file.

0000000  9af0 7629 516f b713 d53e 4d43 3077 3531
0000020  178d 6e37 5072 3b31 d827 0c4b 4054 4486
   :
   :
0001040  6824 3322 b2b1 c339 43dc ae90 4f48 30b7
0001060  3f32 de04 bb5c b3ec 84ed a3b5 48df cc58  <- 576byte
0001100  a6bc 1d8a 5565 a5f0 e54f 9b50 c060 e4cc
0001120  3409 3432 0fe6 01f9 aba6 2f9f 3431 0c0e
0001140  578d bb0f 33e7 c61c fb62 c4ec dc17 f3f8
0001160  54ad f13d 837c 6e4c 2bc6 49e0 5290 669f
0001200  ee49 af43 3b2a 775f 3367 b1cd 6115 084d
0001220  02c7 91aa df12 471a 6db0 cbe2 b0b9 d100
0001240  06fa 8a1f 6350 b724 8aca 6209 e535 bdca
0001260  1c5c 9062 1b79 3793 264c a989 ab51 91d9
0001300  5c3e 6b23 1e02 25ee 191e 1f6e 08f6 70b6
0001320  a6bc 1d8a 5465 6df4 e54f 9b50 c0e3 caf2
   :
   :

2.2 to convert from older firmware RVF files to MP3 files

To convert from older firmware RVF files to MP3 files, you need skip the first 576 bytes for each RVF files.
Then converting process is the same as mentioned in 1.2 to convert from RVF file to MP3 file above.

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