BASSmix

BASS_Mixer_ChannelGetLevelEx

Retrieves the level of a mixer source channel.

DWORD BASS_Mixer_ChannelGetLevelEx(
    DWORD handle,
    float *levels,
    float length,
    DWORD flags
);

Parameters

levels

An array to receive the levels.

length

The amount of data to inspect to calculate the level, in seconds. The maximum is 1 second. Less data than requested may be used if the full amount is not available, eg. if the source's buffer (determined by the BASS_CONFIG_MIXER_BUFFER config option) is shorter.

flags

A combination of these flags.

BASS_LEVEL_MONO	Get a mono level. If neither this or the BASS_LEVEL_STEREO flag is used, then a separate level is retrieved for each channel; the number of channels is available from BASS_WASAPI_GetInfo.
BASS_LEVEL_STEREO	Get a stereo level. The left level will be from the even channels, and the right level will be from the odd channels. If there are an odd number of channels then the left and right levels will both include all channels.
BASS_LEVEL_RMS	Get the RMS level. Otherwise the peak level.

Return value

If an error occurs, -1 is returned, use BASS_ErrorGetCode to get the error code. If successful, the level of the left channel is returned in the low word (low 16-bits), and the level of the right channel is returned in the high word (high 16-bits). If the channel is mono, then the low word is duplicated in the high word. The level ranges linearly from 0 (silent) to 32768 (max). 0 will be returned when a channel is stalled.

Error codes

BASS_ERROR_HANDLE	handle is not plugged into a mixer.
BASS_ERROR_NOTAVAIL	The channel does not have buffering (BASS_MIXER_BUFFER) enabled.
BASS_ERROR_NOPLAY	The mixer is not playing.

Remarks

This function is like the standard BASS_ChannelGetLevelEx, but it gets the level from the channel's buffer instead of decoding data from the channel, which means that the mixer does not miss out on any data. In order to do this, the source channel must have buffering enabled via the BASS_MIXER_BUFFER flag.

This function measures the level of the channel's sample data, not its level in the mixer output. It includes the effect of any DSP/FX set on the channel, but not the effect of the channel's BASS_ATTRIB_VOL or BASS_ATTRIB_PAN attributes or matrix mixing or any envelope set via BASS_Mixer_ChannelSetEnvelope.

If the mixer is being played by BASS, the returned level will be in sync with what is currently being heard from the mixer. If another output system is being used, the BASS_ATTRIB_MIXER_LATENCY option can be used to tell the mixer what the latency is so that it can be taken account of, otherwise the channel's most recent data will be used to get the level. The BASS_CONFIG_MIXER_BUFFER config option determines how far back the level will be available from, so it should be set high enough to cover any latency.