I m want to extract the scene change timestamp using the scene change detection from ffmpeg. I have to run it on a few hundreds of videos , so i wanted to use a python subprocess to loop over all the content of a folder.
My problem is that the command that i was using for getting these values on a single video involve piping the output to a file which seems to not be an option from inside a subprocess call.
this is my code :
p=subprocess.check_output(["ffmpeg", "-i", sourcedir+"/"+name+".mpg","-filter:v", "select='gt(scene,0.4)',showinfo\"","-f","null","-","2>","output"])
this one tell ffmpeg need an output
output = "./result/"+name
p=subprocess.check_output(["ffmpeg", "-i", sourcedir+"/"+name+".mpg","-filter:v", "select='gt(scene,0.4)',metadata=print:file=output","-an","-f","null","-"])
this one give me no error but doesn't create the file
this is the original command that i use directly with ffmpeg:
ffmpeg -i input.flv -filter:v "select='gt(scene,0.4)',showinfo" -f null - 2> ffout
I just need the ouput of this command to be written to a file, anyone see how i could make it work?
is there a better way then subprocess ? or just another way ? will it be easier in C?
You can redirect the stderr output directly from Python without any need for shell=True which can lead to shell injection.
It's as simple as:
with open(output_path, 'w') as f:
subprocess.check_call(cmd, stderr=f)
Things are easier in your case if you use the shell argument of the subprocess command and it should behave the same. When using the shell command, you can pass in a string as the command rather then a list of args.
cmd = "ffmpeg -i {0} -filter:v \"select='gt(scene,0.4)',showinfo\" -f {1} - 2> ffout".format(inputName, outputFile)
p=subprocess.check_output(cmd, shell=True)
If you want to pass arguments, you can easily format your string
Related
C:\Windows\System32> ffmpeg -i D:\devaraj\KPIX_test.ts -vf "blackframe" -an -f n
ull - 2>&1|find "Parsed" > D:\devaraj\info.txt
this works fine , writes the file info.txt
subprocess.call('ffmpeg' ,'-i', 'D:\devaraj\KPIX_test.ts' ,'-vf', '"blackframe"', 'D:\devaraj\KPIX_textfinal.mp3', '- 2>&1>','|','find', '"Parsed"', '>' ,'D:\devaraj\info.txt', 'shell=True')
gives an error buffer size must be integer
were as
subprocess.call('ffmpeg -i D:\devaraj\KPIX_test.ts -vf "blackframe" -an -f n
ull - 2>&1|find "Parsed" > D:\devaraj\info.txt', shell=True)
gives an error
'find' is not recognized as an internal or external command,
operable program or batch file.
any help would be appreciated from d bottom of heart
you should use native python methods to get filtered ffmpeg output:
ffmpeg -i D:\devaraj\KPIX_test.ts -vf "blackframe" -an -f null - 2>&1|find "Parsed"
To do this, you'd normally require check_output but this particular example is known to provide the required info but exit with a non-zero return code (using run from Python 3.5 would work, though)
So I'll use Popen instead. It becomes (as list, without all redirections and filters), then read all output from process standard output:
p = subprocess.Popen(["ffmpeg","-i",r"D:\devaraj\KPIX_test.ts",
"-vf","blackframe","-an","-f","null"],stdout=subprocess.PIPE,stderr=subprocess.STDOUT)
output = p.stdout.read()
You don't need shell=True, and it merges error & output streams in the output variable.
Now output contains the output of ffmpeg command. Let's decode it (to get a string) and split the lines, check if the string is in the lines:
for line in output.decode().splitlines(): # python 2: output.splitlines()
if "Parsed" in line:
print(line.rstrip()) # or store it in a file, string, whatever
for a process outputting a lot more text, it would be better to iterate on p.stdout instead of reading the full contents (less memory hungry, allows real-time echo to the console)
I am trying to store an image that is the result of ffmpeg.
Using this command, I have frame.png as an external file output:
ffmpeg -flags2 +export_mvs -i video.avi -vf 'select=gte(n\,200),codecview=mv=pf+bf+bb' -vframes 1 frame.png
I want to be able to load the frame.png directly into python, maybe using openCV but without saving it in the computer.
I thought of something like this:
cmd = "ffmpeg -flags2 +export_mvs -i video.avi -vf 'select=gte(n\,200),codecview=mv=pf+bf+bb' -vframes 1 frame.png"
img = cv.imread(sp.Popen(cmd, shell=True, stdout = sp.PIPE, stderr = sp.PIPE).communicate()[0])
But I get an error:
TypeError: bad argument type for built-in operation
Any clue how to do this? The idea is, no frame.png should be generated as a file.
You can set the output file as /dev/stdout (you might need to specify the output format with -f)
Then you redirect your output to your python script like so
ffmpeg options /dev/stdout | python your_script.py
Then you can read this question to see how you can read an image from a file object. Just replace StringIO with sys.stdin
Using Python 2.7 on Raspberry Pi B+, I want to call the command "raspistill -o image.jpg" from Python and find using this is recommended:
from subprocress import call
call(["raspistill","-o image.jpg"])
However, this doesn't work since the image.jpg isn't created although outside Python,
raspistill -o
does create the file.
Next try is to first create the image file and writing to it.
f = open("image.jpg","w")
call(["raspistill","-o image.jpg"], stdout = f)
Now the image file is created, but nothing is written to it: its size remains 0. So how can I get this to work?
Thank you.
You are passing -o image.jpg as a single argument. You should pass them like two. Here is how:
call(["raspistill", "-o", "image.jpg"])
The way you did it it's like calling raspistill "-o image.jpg" from the command line, which will likely result in an error.
First, you're creating and truncating the file image.jpg:
f = open("image.jpg","w")
Then you're sending raspistill's stdout to that same file:
call(["raspistill","-o image.jpg"], stdout = f)
When you eventually get around to close-ing the file in Python, now image.jpg is just going to hold whatever raspistill wrote to stdout. Or, if you never close it, it'll be that minus the last buffer, which may be nothing at all.
Meanwhile, you're also trying to get raspistill to create a file with the same name, by passing it as part of the -o argument. You're doing that wrong, as Ionut Hulub's answer explains. Some programs will take "-o image.jpg" "-oimage.jpg", and "-o", "image.jpg" as meaning the same thing, some won't. But, even if this one does, at best you've now got two programs fighting over what file gets created and written as image.jpg.
If raspistill has an option to write the still to stdout, then you can use that option, together with passing stdout=f, and making sure to close the file. Or, if it has an option to write to a filename, then you can use that option. But doing both is not going to work.
If you don't know how to split the command, you can use shlex.split. For example,
>>> import shlex
>>> args = shlex.split('raspistill -o image.jpg')
>>> args
['raspistill', '-o', 'image.jpg']
>>> call(args)
I'm attempting to create a looped video file by calling ffmpeg from the python subprocess library. Here's the part that's giving me problems:
import subprocess as sp
sp.Popen(['ffmpeg', '-f', 'concat', '-i', "<(for f in ~/Desktop/*.mp4; do echo \"file \'$f\'\"; done)", "-c", "copy", "~/Desktop/sample3.mp4"])
With the above code I'm getting the following error:
<(for f in /home/delta/Desktop/*.mp4; do echo "file '$f'"; done): No such file or directory
I did find a similarly phrased question here. But I'm not sure how the solution might apply to solving my issue.
Following the advice in the comments and looking elsewhere I ended up changing the code to this:
sp.Popen("ffmpeg -f concat -i <(for f in ~/Desktop/*.mp4; do echo \"file \'$f\'\"; done) -c copy ~/Desktop/sample3.mp4",
shell=True, executable="/bin/bash")
--which works fine. – moorej
If you need to parameterize input and output files, consider breaking out your parameters:
# sample variables
inputDirectory = os.path.expanduser('~/Desktop')
outputDirectory = os.path.expanduser('~/dest.mp4')
sp.Popen(['''ffmpef -f concat -i <(for f in "$1"/*; do
echo "file '$f'";
done) -c copy "$2" ''',
bash, # this becomes $0
inputDirectory, # this becomes $1
outputDirectory, # this becomes $2
], shell=True, executable="/bin/bash")
...as this ensures that your code won't do untoward things even when given an input directory with a hostile name like /uploads/$(rm -rf ~)'$(rm -rf ~)'. (ffmpeg is likely to fail to parse an input file with such a name, and if there's any video you don't want included in the current working directory but we'd need to know the escaping rules it uses to avoid that; but it's far better for ffmpeg to fail than to execute arbitrary code).
I'm trying to write an svn pre-commit hook in python. Part of this involves checking the diff file to see if there are any actual file changes (as opposed to just property changes).
I have a working grep command which I can execute fine on the shell
grep "^\(Added: \|Modified: \|Deleted: \)" diff filename | grep -v 'svn:'
However when I put it through subprocess.POpen it escapes all my backslashes, which knackers the regexp.
Executing command: ['grep', '"^\\Added: \\|Modified: \\|Deleted: \\)", ...]
How do I avoid this?
NB: I'm aware that I can pipe results between subprocesses and I can do the two greps that way. I need help getting the first one working first though :/
NB2: I also tried using filterdiff --clean instead and couldn't get it to work. Searching for Added, Modified or Deleted lines, removing those with 'svn:' in and checking I had some results seemed to work though.
Python code:
command = ['grep', '"^\(Added: \|Modified: \|Deleted: \)"', filename]
sys.stdout.write('Executing command: %s\n' % (command))
p = subprocess.Popen(command,
stdin = subprocess.PIPE
stdout = subprocess.PIPE
stderr = subprocess.STDOUT
shell = True)
data = p.stdout.read()
if len(data) == 0:
sys.stdout.write("Diff does not contain any file modifications./n")
exit(0)
You need to consider what you want grep to see in its command line arguments.
The first argument needs to be the literal string "^\(Added: \|Modified: \|Deleted: \)", so that means that it shouldn't include the double quotes but should include the backslashes.
The way to express this kind of string is to use Python raw strings:
command = ['grep', r'^\(Added: \|Modified: \|Deleted: \)', filename]
A good way to check what you're actually running is to replace grep by echo so you can at least see what you're passing to the command.