Overview
========

This is a rdesktop specific extension to the RDPSND protocol to
support recording.

The basic protocol is the same as RDPSND (described in rdpsnd.txt),
but with a bunch of new opcodes.

A client indicates to the server that it can support recording by
setting bit 24 (0x00800000) in "Flags" in RDPSND_NEGOTIATE.

New opcodes

        0x27    RDPSND_REC_NEGOTIATE
        0x28    RDPSND_REC_START
        0x29    RDPSND_REC_STOP
        0x2A    RDPSND_REC_DATA
        0x2B    RDPSND_REC_SET_VOLUME

Opcodes
=======

The following is a list of the new opcodes and their payload.

RDPSND_REC_NEGOTIATE
--------------------

Sent immediatly after RDPSND_NEGOTIATE when the client indicates that
it supports recording. Allows the server to determine the
capabilities of the client.

The client should reply with an identical packet, with the relevant
fields filled in, and a filtered list of formats (based on what the
client supports).

 0                   1                   2                   3   
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                             Flags                             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          Left channel         |         Right channel         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          Format count         |            Version            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                              ...                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|           Format tag          |            Channels           |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                        Frames per sec.                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         Bytes per sec.                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          Block align          |        Bits per sample        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          Extra size           |         Extra data ...        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                              ...                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Flags

    Flags for capabilities. Currently unused.

Left channel

    Initial volume for left channel. Reserved when sent from server.

Right channel

    Initial volume for right channel. Reserved when sent from server.

Format count

    Number of format structures following the header.

Version

    Version of the RDPSND record protocol. Current version is 1.

Format tag

    Audio format type as registered at Microsoft.

Channels

    Number of channels per frame.

Frames per sec.

    Frames per second in Hz.

Bytes per sec.

    Number of bytes per second. Should be the product of
    "Frames per sec." and "Block align".

Block align

    The size of each frame. Note that not all bytes may contain
    useful data.

Bits per sample

    Number of bits per sample. Commonly 8 or 16.

Extra size

	Number of bytes of extra information following this format
	description.

Extra data

	Optional extra format data. Contents specific to each format
	type.

RDPSND_REC_START
----------------

Sent from the server to tell the client to start recording.

 0                   1                   2                   3   
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|         Format index          |                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Format index

    Waveform data format in the form of an index to the previously
    negotiated format list.

RDPSND_REC_STOP
---------------

Tells the client to stop sending record data. Must be sent before a
new RDPSND_REC_START is sent.

No payload and no response.

RDPSND_REC_DATA
---------------

Chunk of recorded data. The client is free to choose how much data
should be queued up before a packet is sent. The payload must not
exceed 32768 bytes though.

No response.

 0                   1                   2                   3   
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         Waveform data                         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                              ...                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Waveform data

    Binary waveform data in the format specified by the format index.
    Size defined by the packet boundary.

RDPSND_REC_SET_VOLUME
---------------------

Request from the server to the client to change the input volume.
No response.

 0                   1                   2                   3   
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|          Left channel         |         Right channel         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Left channel

    Volume of left channel in the range [0, 65535].

Right channel

    Volume of right channel in the range [0, 65535].