Recording Callbacks

The current record implementation supports both direct recording and callback-driven asynchronous recording.

Direct Recording

Direct recording returns an audio value immediately.

x = record
y = record(0, 1000, 1)

Current argument meaning:

• device_id
• duration_ms
• channels
• block_ms

For ordinary record(), the engine currently accepts up to three explicit arguments:

• record()
• record(device_id)
• record(device_id, duration_ms)
• record(device_id, duration_ms, channels)

Callback Form

The async form uses a callback name:

h = record(0, -1, 1, 100).cb1

In the current engine:

• the callback form can take up to four arguments: device_id, duration_ms, channels, block_ms
• duration_ms may be -1 for indefinite recording
• channels must currently be 1 or 2
• block_ms must be positive

The callback name after the dot is required in callback mode.

Callback Payload

The current callback payload contains:

• sample_rate
• num_channels
• callback_index
• interleaved

In AUX callback code, this payload is exposed through the input argument. The checked-in example cb1.aux uses:

• in.?index to detect the open call
• in.?data for later audio blocks

That means the callback is invoked in phases:

• callback index 0: open/setup phase
• callback index 1 and later: recorded block delivery

Example

This example is already present in the repo and shows a plotting callback:

function [out,h,ax]=cb1(in)
if in.?index==0
    out = []
    h=figure
    ax = axes(h)
    ax.xlim=[0 10]
else
    out ++= in.?data
    plot(ax, out)
    ax.xlim=[0 10]
    repaint(h)
end

This pattern is useful because the callback can both:

• accumulate captured audio into out
• create and update graphics handles across callback invocations

Handle State During Recording

The runtime recording handle currently carries members such as:

• type
• id
• devID
• fs
• channels
• dur
• block
• durRec
• durLeft
• prog
• active
• paused

These fields are updated while recording progresses, and auxlab2 also attaches callback outputs back onto the handle state when possible.

Notes

• Callback output and preview text may appear in the auxlab2 console.
• In auxlab2, callback failures stop the recording session.
• Recording support depends on an installed playback/recording backend in the active frontend.

Current source basis:

• aux_engine/src/func/record_builtin.cpp
• aux_engine/include/auxe/auxe.h
• auxlab2/src/AuxEngineFacade.cpp
• auxlab2/src/MainWindow.cpp
• auxlab2/cb1.aux