BassBASS_ChannelGetData Method (Int32, Int32, Int32)

[DllImportAttribute("bass")]
public static int BASS_ChannelGetData(
	int handle,
	int[] buffer,
	int length
)

<DllImportAttribute("bass">]
Public Shared Function BASS_ChannelGetData ( 
	handle As Integer,
	<OutAttribute> buffer As Integer(),
	length As Integer
) As Integer

Parameters

handle

Type: SystemInt32
The channel handle... a HCHANNEL, HMUSIC, HSTREAM, or HRECORD.

buffer

Type: SystemInt32
The array (int[]) to receive the data, e.g. when creating the channel stream with default setting, meaning 16-bit samples, an int value contains 2 channels (left and right)!

length

Type: SystemInt32
Number of bytes wanted, and/or the following flags (BASSData):

BASS_DATA_NOREMOVE	Do not remove the data from a recording channel's buffer. This is automatic if the recording channel is using a RECORDPROC callback function. This flag is ignored on other channel types.
BASS_DATA_AVAILABLE	Query the amount of data the channel has buffered. This flag is primarily of use when recording, and can't be used with decoding channels as they do not have playback buffers. buffer can be when using this flag.

Return Value

When requesting sample data, the number of bytes written to buffer will be returned (not necessarily the same as the number of bytes read when using the BASS_DATA_FLOAT flag).

When using the BASS_DATA_AVAILABLE flag, the number of bytes in the channel's buffer is returned.

This function can only return as much data as has been written to the channel's buffer, so it may not always be possible to get the amount of data requested, especially if you request large amounts. If you really do need large amounts, then increase the buffer lengths (BASS_CONFIG_BUFFER). The BASS_DATA_AVAILABLE flag can be used to check how much data a channel's buffer contains at any time, including when stopped or stalled.

When requesting data from a "decoding channel" (BASS_STREAM_DECODE or BASS_MUSIC_DECODE was used at creation), there are no intermediate buffers involved, so as much data as is available can be decoded in one go.

When retrieving sample data, the returned data is in the standard Windows PCM format: 8-bit samples are unsigned, 16-bit samples are signed, 32-bit floating-point samples range from -1 to 1 (not clipped, so can actually be outside this range). That's unless the BASS_DATA_FLOAT flag is used, in which case, the sample data will be converted to 32-bit floating-point (if it isn't already).

This function is most useful if you wish to visualize (eg. spectrum analyze) the sound.

int length = (int)Bass.BASS_ChannelSeconds2Bytes(channel, 0.03); // 30ms window
int[] data = new int[length/4]; // 2 x 16-bit and length in is bytes
length = Bass.BASS_ChannelGetData(channel, data, length);
// further processing of length/4 array elements...where each int value represents a stereo pair

Dim length As Integer = CInt(Bass.BASS_ChannelSeconds2Bytes(channel, 0.03))
Dim data(length/4 - 1) As Integer  ' 2 x 16-bit and length in is bytes
length = Bass.BASS_ChannelGetData(channel, data, length)
' further processing of length/4 array elements...where each int value represents a stereo pair

Reference