ffmpeg无法检测文件，而os可以

Question

Issue

I'm trying to load images in a sub-directory with files named:

• .\\images\\image0.png
• .\\images\\image1.png
• .\\images\\image2.png
• .\\images\\image3.png
• ... etc ...
• .\\images\\image8.png
• .\\images\\image9.png

When I run code:

 print os.path.exists('.\\images\\image0.png')
 cmd = "ffmpeg -f image2 -r 20 -i .\\images\\image%01d.png -c:v libx264 -r 20 .\\images\\output.mp4"
 os.system(cmd)

it results in:

 True
 //blah blah blah ffmpeg start up stuff blah blah blah 

 [image2 @ 00000000026ceda0] Could find no file with with path '.\images\image%01
 d.png' and index in the range 0-4
 .\images\image%01d.png: No such file or directory

I even checked:

 os.getcwd()

Was the right path.

Could someone shed some light on my issue? I'm pretty sure my ffmpeg command is correct (it has worked for me in the past). I'm wondering if there might be a reason that ffmpeg won't recognize my current working directory? (And won't take that relative path as a result?)

Thanks! Advice/suggestions will be greatly appreciated.

Answer 1

The problem is that you've set up your system so every new cmd.exe shell immediately cd's to your Documents directory, so ffmpeg is trying to run there.

The obvious way around that is to just give ffmpeg absolute paths instead of relative:

images = os.path.abspath('.\\images')
cmd = "ffmpeg -f image2 -r 20 -i {}\\image%01d.png -c:v libx264 -r 20 {}\\output.mp4".format(images, images)

Alternatively, you can always stick a cd command into what you send to the system function:

curpath = os.path.abspath(os.getcwd())
cmd = "cd {} && ffmpeg -f image2 -r 20 -i .\\images\\image%01d.png -c:v libx264 -r 20 .\\images\\output.mp4".format(curpath)

However, the best solution is to stop using system entirely, as the documentation for system suggests, and leave the shell out of it:

cmd = "ffmpeg -f image2 -r 20 -i .\\images\\image%01d.png -c:v libx264 -r 20 .\\images\\output.mp4"
subprocess.check_call(cmd)

(Someone is invariably going to suggest in a comment that you can't use a string with subprocess unless shell=True . That's true on Unix, but not on Windows. In fact, on Windows, if you pass a list of parameters, subprocess will just join them up into a string to pass to CreateProcess . If you don't know how to escape your parameters properly for Windows, a list can still be a good idea—but if you've got a perfectly good command line, just use it.)