In a multitasking environment the decoder cannot be guaranteed to have enough system resources available to provide audio data for the output device in realtime. Thus the decoder must be ahead of the output device and store the decoded data into a buffer so that there is always something to play in case the decoder temporarily cannot keep up the pace. Sometimes even the buffer is not enough but the output device plays all the data in the buffer before the decoder provides more. This is called buffer underrun. When a buffer underrun occurs, the playback is paused and resumed again when the decoder has provided more data to the buffer.

Buffer Size

Sets the buffer size in seconds. You can calculate the buffer size in bytes using the following formula:

[buffer size in bytes] =

[buffer size in seconds] * [sample rate] * [channel count] * [bit resolution] / 8

Buffer pre-fill

When the playback restarts (starting a new track when stopped, setting the playback position or when a buffer underrun occurs) buffer is filled up to the percentage given by this setting before the playback is started.

When playing multiple tracks in a row, Apollo tries to play the tracks without stopping the playback of the output device in between them. This is possible if the two adjacent tracks have the same sample frequency, channel count and bit resolution. If these conditions are not met, the device will be stopped and the settings of continuous play are not applied.

Currently four possible continuous play modes are supported: gapless playback, silent pause, crossfade and crossfade without fade in.

Gapless playback plays tracks without any pause between them.

The silent pause does not pause the output device for the given amount of time, but instead it feeds the buffer with silent data. You can hear this for instance when you are using a echoing DSP plug-in (the end of the song echoes during the silent part between tracks). Setting the pause length to 0 seconds means gapless playback. Some MiniDisc recorders automatically recognizes silent sections of three seconds as the end of track markes, so this option might be useful when creating your own MiniDisc recordings.

With the crossfade modes the playback of the next track starts (or fades in) while the current track fades out. This allows listening to tracks in a radio-like manner. You cannot set the exact length of the crossfade, but instead you provide the preferred length. This is because the crossfade is performed with the yet unplayed buffered data and the buffer cannot be guaranteed to be full. From this follows the fact that the crossfade cannot be longer than the used buffer size. Thus you should always use a rather large buffer with the crossfade modes.

The chosen crossfade mode will also be used when the Control key is held down and a new track is selected while already playing. It is naturally required that the two tracks have the same sample frequency, channel count and bit resolution.

To use the continuous play modes in a more efficient way, you can set Apollo to skip the unwanted silence in the beginning and/or in the end of the tracks. And because people have different opinions on what is to be considered silence, the threshold of silence can be set.

Note that the skipping of silence in the end of tracks is (again) done within the buffer. Thus if there is more silence in the end of a track than there is space in the buffer, only a part of the silence will be skipped. Also note that skipping the silence in the end of a track takes buffer space from the crossfader and thus the preferred crossfade length might not be applicable resulting in a shorter crossfade.