Looping a sound
A looped sound will repeat endlessly without any gap between its end and start. It is up to the sound artist to ensure that the end and start of the file match up however, or there will be a "pop" as the waveform jumps from one shape to another.
GoldSrc and Source detect looped sounds ONLY through cue points embedded in the file. This is a WAV-only feature, so MP3s cannot be looped. Microsoft ADPCM compressed WAVs can be looped, but due to the way they are encoded, there may a pop when the sound restarts if the sound is shorter than a few seconds.
Looping a WAV
These free programs can add cue points to a WAV:
- GoldWave (trialware)
- Wavosaur (freeware)
- LoopAuditioneer (free and open source)
- OcenAudio (freeware)
GoldWave
Open Goldwave and open the sound you want to loop. Click the cues icon. () Then in the new window click on the New button and add a cue point At Start. Then click New for another cue point and add a point At End. So it looks similar to this:
Wavosaur
Open Wavosaur and open the sound you want to loop. Go to Tools > Loop > Create loop points
. It should create loop points. You can change their positions by dragging them.
After that, click "Save" or "Save As".
Create loop points
function in Wavosaur. If this happens, try setting only the starting cue by using a marker instead (Tools > Loop > Create marker
).With a hex editor
Appending the following bytes to the end of a non-looping WAV file will make it loop in its entirety:
63 75 65 20 1C 00 00 00 01 00 00 00 01 00 00 00 00 00 00 00 64 61 74 61 00 00 00 00 00 00 00 00 00 00 00 00
cue.bin
, then run cat my_nonlooping_sound.wav cue.bin > my_looping_sound.wav
.The bash shell script used to generate the above cue chunk is provided below, based upon documentation from recordingblogs.com.
#!/bin/bash
# Wave file cue chunk according to https://www.recordingblogs.com/wiki/cue-chunk-of-a-wave-file
# Original script by SavageX; permission is granted to modify as needed.
ECHO="echo -en"
OUT="cue.bin"
function append_bytes() {
$ECHO $1 >> $OUT
}
function append_cue() {
OUT=$1
# chunk ID, "cue "
append_bytes "cue\x20"
# size of the chunk: (12 + 24) - 8 = 28
# Why -8? ID and size don't count.
append_bytes "\x1C\x00\x00\x00"
# number of data points: 1
append_bytes "\x01\x00\x00\x00"
# ID of data point: 1
append_bytes "\x01\x00\x00\x00"
# position: If there is no playlist chunk, this is zero
append_bytes "\x00\x00\x00\x00"
# data chunk ID
append_bytes "data"
# chunk start: 0
append_bytes "\x00\x00\x00\x00"
# block start: 0
append_bytes "\x00\x00\x00\x00"
# sample start: 0
append_bytes "\x00\x00\x00\x00"
}
rm -f cue.bin
append_cue cue.bin
|
Cue location
Your cues do not have to be at the start and end of the file. If you place them in the middle Source will start playing the sound normally, then when it reaches the end cue will loop back to the start cue. From then on only what's between the cues will play.
This can be used to give a sound a "winding up" effect that only plays once (e.g. a motor starting).
Looping an MP3
In Source, MP3 files can't be looped with start/end queues like a WAV. A logic_timer
can be a good workaround; have it start playing the sound again after it has fully played (or has played to the point desired).
This could also be done using User I/O from the ambient_generic
to itself, and an input delay.
See also
External links
- Looping Menu Music - An Interlopers.net Tutorial on Soundlooping