I'm trying to run a for loop in cmd that looks like this:
for %f in (*.mp4) do (
set outfile=%f:mp4=mp3%
ffmpeg -i %f -vn -ar 44100 -ac 1 -b:a 32k -f mp3 %outfile%
)
The script is supposed to grab all *.mp4 files, run the ffmpeg command on them, then name the resultant file identical as the mp4 with only the extension changed to *.mp3.
It doesn't work. The output is literally named %outfile%. If I had to guess, there's something wrong with the initialization or calling of the outfile variable. I also thought that perhaps it is a data type issue. %f is perhaps a pointer, not a string, so some kind of string extraction or type conversion is needed.
How can I set and use a filename as a string variable in cmd?
The best way to do it is not to do it. Don't store inside a variable something that can be directly retrieved from the for replaceable parameter.
for %f in (*.mp4) do ffmpeg -i "%f" -vn -ar 44100 -ac 1 -b:a 32k -f mp3 "%~nf.mp3"
The for command replaceable parameter (%f in your case) allow the use of some modifiers (see for /?). %~nf is the name, without extension, of the file being referenced by %f
But, if your only option is to do it, here you can find some ways to deal with the problem.
Related
This question already has answers here:
While loop stops reading after the first line in Bash
(5 answers)
Closed 2 years ago.
I have three .wav files in my folder and I want to convert them into .mp3 with ffmpeg.
I wrote this bash script, but when I execute it, only the first one is converted to mp3.
What should I do to make script keep going through my files?
This is the script:
#!/bin/bash
find . -name '*.wav' | while read f; do
ffmpeg -i "$f" -ab 320k -ac 2 "${f%.*}.mp3"
done
Use the -nostdin flag to disable interactive mode,
ffmpeg -nostdin -i "$f" -ab 320k -ac 2 "${f%.*}.mp3"
or have ffmpeg read its input from the controlling terminal instead of stdin.
ffmpeg -i "$f" -ab 320k -ac 2 "${f%.*}.mp3" </dev/tty
See the -stdin/-nostdin flags in the ffmpeg documentation
If you do need find (for looking in subdirectories or performing more advanced filtering), try this:
find ./ -name "*.wav" -exec sh -c 'ffmpeg -i "$1" -ab 320k -ac 2 "$(basename "$1" wav).mp3"' _ {} \;
Piping the output of find to the while loop has two drawbacks:
It fails in the (probably rare) situation where a matched filename contains a newline character.
ffmpeg, for some reason unknown to me, will read from standard input, which interferes with the read command. This is easy to fix, by simply redirecting standard input from /dev/null, i.e. find ... | while read f; do ffmpeg ... < /dev/null; done.
In any case, don't store commands in variable names and evaluate them using eval. It's dangerous and a bad habit to get into. Use a shell function if you really need to factor out the actual command line.
No reason for find, just use bash wildcard globbing
#!/bin/bash
for name in *.wav; do
ffmpeg -i "$name" -ab 320k -ac 2 "${name%.*}.mp3"
done
this is a beginner's question but i can't figure out the answer after looking into it for several days:
I want ffmpeg to extract the audio portion of a video and save it in an .ogg container. If i run the following command in terminal it works as expected:
ffmpeg -i example.webm -vn -acodec copy example.ogg
For convenience, i want to do this in a script. However, if i pass a variable to ffmpeg it apparently just considers the first word and produces the error "No such file or directory".
I noticed that my terminal escapes spaces by a \ so i included this in my script. This doesn't solve the problem though.
Can someone please explain to me, why ffmpeg doesn't consider the whole variable that is passed to it in a script while working correctly when getting passed the same content in the terminal?
This is my script that passes the filename with spaces escaped by \ to ffmpeg:
#!/bin/bash
titelschr=$(echo $# | sed "s/ /\\\ /g")
titelohne=$(echo $titelschr | cut -d. -f 1)
titelogg=$(echo -e ${titelohne}.ogg)
ffmpeg -i $titelschr -vn -acodec copy $titelogg
Thank you very much in advance!
You need to quote variable expansions, try this :
#!/usr/bin/env bash
titelschr=$1
titelogg="${titelschr%.*}.ogg"
ffmpeg -i "$titelschr" -vn -acodec copy "$titelogg"
call with :
bash test.sh "Some video file.mp4"
This way, you don't need to escape spaces.
I am using using ffmpeg to trim and join several audio files. The ouput audio file can be played as a normal file, but when I open it in some C# codes, exceptions are always throwing, says "MP3 Header is missing". I am new to ffmpeg and I googled for many times but seems no one is encountering this problem.
Here is my ffmpeg command to trim an audio file:
ffmpeg -i input_1.mp3 -ss 00:00:00.000 -to 00:00:01.000 -acodec libmp3lame 1.mp3
(The input audio format can be mp3/wma/wav/m4a/aac)
And the following is for joining all the audio files:
ffmpeg -safe 0 -f concat -i list.txt -acodec libmp3lame join.mp3
The list.txt contents:
file C:\\1.mp3
file C:\\2.mp3
file C:\\3.mp3
Problem soved! Thanks to Gyan's comment under my question.
The main point:
Make sure all converted files have same sampling rate and channel count i.e. add -ar 44100 -ac 2
The above parameters did solve my problem.
How to use the command line tool ffmpeg on Windows to split a sound file to multiple sound files without changing the sound properties same everything each one is fixed 30 seconds length. I got this manual example from here:
ffmpeg -i long.mp3 -acodec copy -ss 00:00:00 -t 00:00:30 half1.mp3
ffmpeg -i long.mp3 -acodec copy -ss 00:00:30 -t 00:00:30 half2.mp3
But is there a way to tell it to split the input file to equally sound files each one is 30 seconds and the last one is the remaining what ever length.
You can use the segment muxer.
ffmpeg -i long.mp3 -acodec copy -vn -f segment -segment_time 30 half%d.mp3
Add -segment_start_number 1 to start segment numbering from 1.
ffmpeg has concat option for this but all streams start working really bad and breaking sound after a day of streaming.
I tried looking at loops but i couldnt figure out how to execute a loop with ffmpeg command so it transcodes all files in 1 directory
/lely/ffmpeg -y -re -i /home/ftp/kid1.mp4 -vcodec copy -acodec copy -dts_delta_threshold 1000 -ar 44100 -ab 32k -f flv rtmp://10.0.0.17:1935/live/kid
In folder /home/ftp/ there are files kid1, kid2, kid3 - all *.mp4 files
So basically i would like a loop to change the input to next file every time previous ends.
Maybe you could use find and xargs to help you feed the files for ffmpeg:
find /home/ftp -name "*.mp4" | xargs -I $ /lely/ffmpeg -y -re -i $ -vcodec copy -acodec copy -dts_delta_threshold 1000 -ar 44100 -ab 32k -f flv rtmp://10.0.0.17:1935/live/kid
Here you first ask find to look for all mp3 files in /home/ftp.
Then you feed the results to xargs. For xargs you tell it to replace input it receives with token $ in your ffmpeg string.
You can concatenate the video files to a "named pipe" and use the pipe as a source for ffmpeg.
For example:
mkfifo pipeFile # create a FIFO file (named pipe)
cat $(find /home/ftp -name "*.mp4") > pipeFile & # concatenate video files do the pipe (do not forget the "&" for running in background)
/lely/ffmpeg -y -re -i pipeFile -vcodec copy -acodec copy -dts_delta_threshold 1000 -ar 44100 -ab 32k -f flv rtmp://10.0.0.17:1935/live/kid # run ffmpeg with the pipe as the input
Notes:
The order of files in the input will be that the find generates. You can add a "sort" command after the find to produce files in a sorted manner.
I have not tested this, since a I do not have ffmpeg installed. However, it should work :-)