AssumeTFF().SeparateFields().SelectEvery(4, 0, 3).Weave() add 1 frame: why?

[marcorocchini]

Hi ****,
in attachement I have do a video of my cat

when I load it on virtualdub using the fmmpeg plugin OR using this avisynth script:

FFVideoSource("C:\Users\Administrator\Desktop\gatto\GOPR1406.MP4")

duration of the video is: 5.78 seconds



But when I load it on virtualdub using this script:

FFVideoSource("C:\Users\Administrator\Desktop\gatto\GOPR1406.MP4")
AssumeTFF().SeparateFields().SelectEvery(4, 0, 3).Weave()

duration of the video become 5,80 seconds



can someone tell me why? How can I get 5,78 sec using the

AssumeTFF().SeparateFields().SelectEvery(4, 0, 3).Weave()

line? thanks

[jagabo]

The source has an odd number of frames and you're cutting the number of frames by half. You can't have half a frame at the end so it's being padded to fill out the last half frame.

[marcorocchini]

thanks jagabo, I understand but what can I do?
In timeline I have the video track that have +1 frame of the audio track

[ndjamena]

AssumeTFF().SeparateFields().SelectEvery(4, 0, 3).Weave().Trim(0, last.FrameCount)

[jagabo]

The output video can only be 20 ms (the duration of one frame of the source) shorter or longer than the source.

[marcorocchini]

my problem is that:

from the gopr1406.mp4 I extract audio with ffmpeg using:

ffmpeg.exe -y -i gopr1406.mp4 -filter_complex "[0:1] volume=1.5" -c:a pcm_s16le gopr1406.wav

and this .wav have, in timeline, have duration of 05 sec 19 frames

but using avisynth with the script

FFVideoSource("C:\Users\Administrator\Desktop\gatto\GOPR1406.MP4")
AssumeTFF().SeparateFields().SelectEvery(4, 0, 3).Weave()

or AssumeTFF().SeparateFields().SelectEvery(4, 0, 3).Weave().Trim(0, last.FrameCount)

I have the video track that are 1 frames in excess (have duration of 5sec and 20 frames) so my nle don't "attach audio-video"
how can I help my cat?

[ndjamena]

Oh, right, you're halving the frame rate. *2 /2 /2

Um...

That would mean each frame has twice the duration, if there were an odd number of video frames in the source then it's simply not possible to match that length, you have no choice but to extend the audio.

[marcorocchini]

AssumeTFF().SeparateFields().SelectEvery(4, 0, 3).Weave().Trim(0, last.FrameCount)

tryed but seems don't change the +1 frame problem.

Can I tell to avisynth that have to trim 0 : lenghtOfGOPR1406.wav?

[jagabo]

You cannot trim a video to half a frame accuracy.

ndjamena's script had a few problems. last.FrameCount is the number of frames in the original clip, not the ~half length interlaced clip. FrameCount is the number of frames, not the number of the last frame (since the first frame is 0 the last frame is FrameCount-1). And Trim() includes the last frame in trim. So the correct command should have been:

AssumeTFF().SeparateFields().SelectEvery(4, 0, 3).Weave().Trim(0, last.FrameCount/2-1)

But that will give you a video that's 20 ms shorter than the original audio rather than 20 ms longer. You'll have to trim the audio too.

[marcorocchini]

FFVideoSource("C:\Users\Administrator\Desktop\gatto\GOPR1406.MP4")
AssumeTFF().SeparateFields().SelectEvery(4, 0, 3).Weave().Trim(0, last.FrameCount/2-2)

in fact with this virtualdub (File information) get a duration of 5,72 second (should be 5,78) and in timeline duration is 5 sec and 18 frames (should be 5 sec and 19 frames to match audio)

[jagabo]

I fixed the script before you posted. It ends in -1 now rather than -2.

And, once again, YOU WILL NEVER GET S 5.78 SECOND CLIP WITH 25 FPS VIDEO.

[marcorocchini]

5,76 but it's ok in timeline!! thanks