RFC 978

VOICE FILE INTERCHANGE PROTOCOL (VFIP) 🎀

RFC 978 🌸 February 1986

Network Working Group 💖

Authors: J. K. Reynolds (ISI), R. Gillmann (Inner Loop), W. A. Brackenridge (Alembic), A. Witkowski (Inner Loop), and J. Postel (ISI) 👑

Okay bestie, this is a whole squad of authors! 🫶 The title block doesn't list a category or say what it obsoletes or updates, so there's nothing more to add up there.

Status of This Memo ✨

This memo describes a proposed voice file interchange format for use in the ARPA-Internet community. Suggestions for improvement are encouraged, so send them in! 💌 Distribution of this memo is unlimited 🌈

1. Introduction 🦋

Okay so VFIP is all about letting different systems swap different kinds of speech files with each other, no drama 💅 Right now there are tons of different voice implementations out there, but nobody has set a real standard that's built for them to be compatible with each other 😭 And voice is blowing up, especially in Multimedia Mail, so we really need standardized speech living in one common data structure. It's giving organized ✨

VFIP defines a header that describes the voice data. The 18-byte header holds:

• the identifier 🆔
• the header version number 🔢
• the header length 📏
• a DTMF mask for Touch-Tones ☎️
• the recording rate in bits per second 🎧
• the total time in deci-seconds (tenths of a second) ⏱️
• the encoding/recording method (see Figure 1) 🎙️

2. The Voice File Interchange Protocol Header 💅

The Voice File Interchange Protocol header is organized like this, bestie 🍓

2.1. The Header Version Number

The version number is 1-byte. This first version is number one 🥰

2.2. The Header Length

The length is a 1-byte field that tells you the length of the entire header in bytes. For this first version, the length is 18 (bytes) 💜

2.3. The DTMF Mask

This field describes what is known about DTMF Touch-Tones in the data. It's made of 16 flag bits that show what's known about particular DTMF tones. The 16 possible DTMF tones, in order, are: 0 1 2 3 4 5 6 7 8 9 # * A B C D. The low order bit of the field is tone 0 🔢

A 1-bit means the matching tone is guaranteed NOT to be in the speech file 🙅‍♀️ A 0-bit means it may or may not be in there. So a field of 16 zeros means nothing is known about the tones, and a field of 16 ones means there are no tones in the file at all 🫠

2.4. Recording Rate

The recording rate is a 32-bit field. It's the approximate rate in bits/second of the method used to record the speech. For variable rate methods, this may be very approximate 🎵

2.5. Total Time

This is a 32-bit number that shows the total time of the recording in deci-seconds. For example, 600 means 1 minute of speech ⏰

2.6. Methods of Encoding/Recording

This 6-byte ASCII field tells you the method of encoding/recording. Names shorter than six characters get padded out to the right with blanks (the ASCII space character, code 32 decimal). When comparing names, they're case insensitive, so no stress 🌷

Some known methods of Encoding/Recording are:

• TI - The Texas Instruments card for the IBM PC [5]. 🤖
• IBM - PC Voice Communications Options. 💻
• NVP-1 and NVP-2 - Network Voice Protocol [1,2]. 🎀
• COMPUT - Computalker card for the IBM PC [4]. 🧸

3. Summary 🦋

This 18-byte header lets speech files get swapped between different systems, and it helps make automatic conversion between formats way easier 🔥 The header doesn't have to be stuck onto the speech file itself. It can also be a separate associated file, if that's more convenient 💖

                   <------------16-bits------------>
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |    Version    |      Length   |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |             -DTMF-            |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |          -Recording-          |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |             -Rate-            |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |            -Total-            |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |             -Time-            |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |       M       |       E       |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |       T       |       H       |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |       O       |       D       |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1 📸

4. Examples 🧚

Example 1 is for one minute of 2400 bps NVP-2 speech. Nothing is known about DTMF tones in the data 🎧

                   <------------16-bits------------>
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |       1       |      18       |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |               0               |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |                               |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |              2400             |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |                               |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |              600              |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |       N       |       V       |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |       P       |       -       |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |       2       |      <sp>     |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Example 1 ✨

Example 2 shows the header for 10 seconds of 1200 bps TI speech. None of the DTMF tones 0-9 show up in the data, but we have no info about the tones *, #, and A-D 🙈

                   <------------16-bits------------>
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |       1       |      18       |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |              1023             |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |                               |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |              1200             |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |                               |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |              100              |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |       T       |       I       |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |      <sp>     |      <sp>     |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |      <sp>     |      <sp>     |
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Example 2 🎀

References 📚

• [1] Cohen, Danny, "Specifications for the Network Voice Protocol (NVP)", RFC 741 (NIC 42444), USC/Information Sciences Institute, January 1976. 🦋
• [2] Cohen, Danny, "A Network Voice Protocol (NVP-II)", USC/Information Sciences Institute, April 1981. 🌸
• [3] O'Leary, G. C., "Local Access Area Facilities for Packet Voice", MIT/LL, October 1980. 🍓
• [4] Computalker, "Compu Phone for the IBM PC/XT", Santa Monica, California, August 1985. 💜
• [5] Texas Instruments, Inc., "The TI Speech Application Tool Kit Guide", TI Part #2232384-1, May 1985. 🤖