GetChannel¶
Set of filters to extract audio channels:
GetChannel returns one or more channels of a multichannel signal.
GetLeftChannel returns the left channel from a stereo signal, and GetRightChannel returns the right.
GetChannels is an alias for GetChannel and can be used interchangeably.
Syntax and Parameters¶
GetChannel (clip, int ch1 [, int ch2, ...])
GetChannels (clip, int ch1 [, int ch2, ...])
GetLeftChannel(clip clip)
GetRightChannel(clip clip)
- clip
Source clip; all audio sample types supported.
- ch1, ch2, ...
Specify what channel(s) to return.
The ordering of the channels is determined by the ordering of the input file, because AviSynth doesn't assume any ordering (see Remarks).
In case of WAV files, the ordering should be as follows:
WAV, 2 channels (stereo)
1
left channel
2
right channel
WAV, 5.1 channels
1
front left channel
2
front right channel
3
front center channel
4
LFE (Subwoofer)
5
rear left channel
6
rear right channel
Remarks¶
Every file format has a different internal channel ordering. The following table gives this internal ordering for some formats (useful for plugin writers), but it is the decoder's task to return the expected channel order. If you use decoders like NicAudio/BassAudio or ffdshow/AC3Filter you don't need to worry about this.
Format
Channel 1
Channel 2
Channel 3
Channel 4
Channel 5
Channel 6
front left
front right
front center
LFE
rear left
rear right
front left
front center
front right
rear left
rear right
LFE
front center
front left
front right
rear left
rear right
LFE
front center
front left
front right
rear left
rear right
LFE
front left
rear left
front center
front right
rear right
LFE
front left
front right
front center
LFE
rear left
rear right
front left
front right
front center
LFE
rear left
rear right
[1] 5.1 DTS: the LFE is on a separate stream (much like on multichannel MPEG2).[2] There is no free version of the AAC specification available online.
Examples¶
Get mono audio from left channel of a WAV file, and dub to video from AVI:
video = AviSource("c:\video.avi") stereo = WavSource("c:\audio2ch.wav") mono = GetLeftChannel(stereo) return AudioDub(video, mono)
Do the same, alternate syntax:
video = AviSource("c:\video.avi") stereo = WavSource("c:\audio2ch.wav") mono = GetChannel(stereo, 1) return AudioDub(video, mono)
Do the same with the audio channels from the AVI file itself:
video = AviSource("c:\video+audio2ch.avi") return GetChannel(video, 1)
- Convert AVI with 5.1 audio to stereo (copy front left and front right)
video = AviSource("c:\video+audio6ch.avi") stereo = GetChannel(video, 1, 2) return AudioDub(video, stereo)
Get front left and front right audio from a 5.1 AVI:
video = AviSource("c:\video+audio6ch.avi") audio = WavSource("c:\video+audio6ch.avi") stereo = GetChannel(audio, 1, 2) return AudioDub(video, stereo)
- Mix 5.1 to stereo - see discussion here.Note returned audio has sample type Float.Normalize is recommended before converting to 16-bit to avoid possible overload.
AviSource("c:\video+audio6ch.avi") DownMix() Normalize() ConvertAudioTo16bit() return Last function DownMix(clip a, float "centergain", float "surroundgain") { a.ConvertAudioToFloat() ## 5.1 WAV channel layout: fl = GetChannel(1) fr = GetChannel(2) fc = GetChannel(3) lf = GetChannel(4) ## (LFE not used) sl = GetChannel(5) sr = GetChannel(6) ## add center gc = Default(centergain, 1.0) * 0.7071 fl = MixAudio(fl, fc, 1.0, gc) fr = MixAudio(fr, fc, 1.0, gc) ## add surround gs = Default(surroundgain, 1.0) * 0.7071 fl = MixAudio(fl, sl, 1.0, gs) fr = MixAudio(fr, sr, 1.0, gs) return AudioDub(a, MergeChannels(fl, fr)) }
Changelog¶
Version |
Changes |
---|---|
AviSynth 2.5.0 |
Added GetChannel and GetChannels filters. |
AviSynth 2.0.3 |
Added GetLeftChannel and GetRightChannel filters. |
$Date: 2022/03/05 18:47:07 $