- Full Error:
Stream specifier 's1:v' in filtergraph description [0]split=2:outputs=2[s0][s1];[s1:v]reverse[s2];[s0][s2]concat=a=0:n=2:v=1[s3] matches no streams.
- Formatted Error
- Code:
instances = (
ffmpeg
.input(self.video_file)
.filter_multi_output(filter_name="split", outputs=2)
)
ordered_edits = []
for i in range(2):
if i%2 == 0:
ordered_edits.append(
instances[i]
)
else:
ordered_edits.append(
instances[i].video.filter(filter_name="reverse")
)
(
ffmpeg
.concat(*ordered_edits, a=0, v=1)
.output('done/output.mp4')
.run(overwrite_output=True))
Looking at the error code, it seems like s1:v should be a valid reference. The only thing I can think of is that there is an issue saving an exclusive video input into a nonspecified output. The files don't actually have any audio, I just want the video.
I'm lost, please help ffmpeg experts of the world!
Using .video is redundant here.
Per the ffmpeg documentation:
17.33 split, asplit
Split input into several identical outputs.
asplit works with audio input, split with video.
The filter accepts a single parameter which specifies the number of outputs. If unspecified, it defaults to 2.
In other words, by using a split filter, you are implicitly stripping audio off of the video. I am not totally sure why s1:v is an error, instead of just a no-op, but it does seem to be the cause of the error.
This works fine for me:
instances = (
ffmpeg
.input("input.mp4")
.filter_multi_output(filter_name="split", outputs=2)
)
ordered_edits = []
for i in range(2):
if i%2 == 0:
ordered_edits.append(
instances[i]
)
else:
ordered_edits.append(
instances[i].filter(filter_name="reverse")
)
(
ffmpeg
.concat(*ordered_edits, a=0, v=1)
.output('output.mp4')
.run(overwrite_output=True))
This produces a video where the input video plays, then plays backwards, which I assume is what was intended.