[avisynth] how to use only FFAudioSource without FFVideoSource

[marcorocchini]

Hi cats

please consider this workingOK.avs

vid=FFVideoSource("V:\GOPR0433.MP4")
aud=FFAudioSource("V:\GOPR0433.MP4")
left = GetChannel(aud, 1)
right = GetChannel(aud, 1)
both=mergechannels(left, right)
audioDub(vid,both)
ConvertAudioTo16Bit()
ConvertToYUY2(interlaced=false)
AssumeTFF().SeparateFields().SelectEvery(4, 0, 3).Weave().trim(0,2482)
AssumeFPS(25)

and then

ffmpeg.exe -y -i workingOK.avs -filter_complex "[0:1] volume=1.1" -c:a pcm_s16le workingOK.wav

But this script need to generate ffindex also for the video part: but I don't need of the video part because I need to generate the workingOK.wav


and 2nd second question: can I tell to avisynth (or ffmpeg?): please use an AGC audio volume level setting?


and 3rd question: can, using ffmpeg, I generate a EmptyAudioFile.wav of silence that have duration of 2482 frames? but this EmptyAudioFile.wav have to be a stereo L+R 16bit 48.000 Khz file

How can modify the .avs so that if outputs only audio and not video? thanks

[poisondeathray]

FFAudioSource("V:\GOPR0433.MP4") to load audio only

Why don't you load the video directly into ffmpeg? (what is the reason for the avs script if you're only interested in audio? )

BlankClip() in avisynth can generate blank audio, but the number of frames and frame rate will determine the duration. (a higher FPS will be shorter clip for the same number of frames; audio doesn't have "frames" - what you want is duration)
blankclip(length=2483, fps=25, stereo=true, audio_rate=48000)

[marcorocchini]

FFAudioSource("V:\GOPR0433.MP4") to load audio only

Why don't you load the video directly into ffmpeg? (what is the reason for the avs script if you're only interested in audio? )

mmmmm I don't remember well (I'm a ***)
but if I don't mistake the reason is that with this procedure audio lenght of the .wav file is exactly the same duration of video .avi lenght