Is it possible to check if a video file has a subtitle using bash and get a simple answer like "yes" or "no". I don't need to know any details about the subtitles.
Maybe using ffmpeg?
This should display a 0 if subtitles are found, and 1 if not found.
ffmpeg -i video -c copy -map 0:s:0 -frames:s 1 -f null - -v 0 -hide_banner; echo $?
Bash
ffmpeg -i $filename 2>&1 | grep "Subtitle:"
Powershell
ffmpeg -i $filename 2>&1 | select-string "Subtitle:"
Explanation:
The ffmpeg command fails if no output file is provided, but the error message contains all information about the input file. The expression 2>&1 redirects error stream to standard output so it can be piped into grep/select-string command.
Related
I was trying to understand this shell script which uses ffmpeg to take an rtmp input stream and send it to a node.js script. But I am having trouble understanding the syntax. What is going on here?
The script:
while :
do
echo "Loop start"
feed_time=$(ffprobe -v error -show_entries format=start_time -of default=noprint_wrappers=1:nokey=1 $RTMP_INPUT)
printf "feed_time value: ${feed_time}"
if [ ! -z "${feed_time}" ]
then
ffmpeg -i $RTMP_INPUT -tune zerolatency -muxdelay 0 -af "afftdn=nf=-20, highpass=f=200, lowpass=f=3000" -vn -sn -dn -f wav -ar 16000 -ac 1 - 2>/dev/null | node src/transcribe.js $feed_time
else
echo "FFprobe returned null as a feed time."
fi
echo "Loop finish"
sleep 3
done
What is feed_time here? What does it represent?
What is this portion doing - 2>/dev/null | node src/transcribe.js $feed_time?
What is the use of sleep 3? Does this mean that we are sending audio stream to node.js in chuncks of 3 seconds?
feed_time variable represents standard output of ffprobe command. This value needs to be passed to node script.
- character doesn't have special meaning in bash, i.e. it is interpreted by ffmpeg command itself (see here). According to ffmpeg docs:
A - character before the stream identifier creates a "negative"
mapping. It disables matching streams from already created mappings.
2>/dev/null is a redirection that sends standard error output of ffmpeg command to /dev/null device, thus effectively discarding the error output (see here). It is done because you want only the standard output (not error output) to be passed to node script.
| is a pipe. It sends standard output of ffmpeg command to standard input of node script.
sleep just delays execution of a script.
I often create bash scripts with bash and pipe the results to bash... When I do this:
echo -e "ffmpeg -loglevel quiet -f lavfi -i nullsrc -t 1 -f null /dev/null\necho foo"|bash
I get
bash: line 2: cho: command not found
Where did the 'e' of 'echo' go? What does ffmpeg do there? Other commands work fine.
Note also:
echo -e "ffmpeg -loglevel quiet -f lavfi -i nullsrc -t 1 -f null /dev/null\necho foo" > /tmp/foo.sh
bash /tmp/foo.sh #works
bash < /tmp/foo.sh #doesn't
ffmpeg also reads from standard input, which it inherits from its parent process, which is the bash process reading your command line. This means ffmpeg is reading the e from echo following the new line.
One fix is to redirection standard input for ffmpeg:
echo -e "ffmpeg -loglevel quiet -f lavfi -i nullsrc -t 1 -f null /dev/null < /dev/null \necho foo"|bash
However, I can't help but point out that there isn't really any reason to run a script like this. If you want it in a separate process, start a subshell:
(
ffmpeg -loglevel quiet -f lavfi -i nullsrc -t 1 -f null /dev/null
echo foo
)
I'm writing a little script to use the webcam on the laptop and then email across the photo to me. The ffmpeg usage has to have a exit code for it to work so with this exit the mail function will not get called. What am I doing wrong?
#!/bin/bash
MAIL_ADDR=user#example.com
ts=`date +%s`
list=$(ls | tail -n 1)
function mcheese(){
mkdir /tmp/cheese
cd /tmp/cheese
echo -e "Cheese " | mutt -s "$TS Cheese" $MAIL_ADDR -a $list
}
function cheese(){
ffmpeg -f video4linux2 -s vga -i /dev/video0 -vframes 3 /tmp/cheese/vid-$ts.%01d.jpg
exit 0
}
cheese
mcheese
You setup list in one directory, then change directory and use it.
This is unlikely to work.
Use bash -x to work out where your script is actually failing.
I'm a newbie to linux scripting and am having an issue with a script that I got from the web and am trying to modify.
Here is the script
#!/bin/bash
if (($# ==0))
then
echo "Usage: flvto3gp [flv files] ..."
exit
fi
while (($# !=0 ))
do
ffmpeg -ss 00:00:10 -t 1 -s 400x300 -i $1 -f mjpeg /home/zavids/rawvids/thumbs/$1.jpg
shift
done
echo "Finished"
echo "\"fakap all those nonsense!\""
echo ""
So I'm grabbing a screenshot from a video and saving it as a jpeg. The problem is the extension of the video file is retained so finished file is video.flv.jpg (for example). How can I get rid of that video extension?
Change this line
ffmpeg -ss 00:00:10 -t 1 -s 400x300 -i $1 -f mjpeg /home/zavids/rawvids/thumbs/$1.jpg
to this
ffmpeg -ss 00:00:10 -t 1 -s 400x300 -i $1 -f mjpeg /home/zavids/rawvids/thumbs/${1%.*}.jpg
That strips the extension from the input file before using it to create the name of the output file, using bash parameter expansion.
You can try to use this :
${string%substring}
It deletes shortest match of $substring from back of $string.
For your case :
${1%.flv}
This code will substitute .flv from the end of your first argument.
You can have a lot of details here too : http://tldp.org/LDP/abs/html/string-manipulation.html
More information about what I want to do here; http://www.studiodust.com/riffmp3.html
I want a way so that my control panel (made with Perl and Webmin) can do this automatically. Right now I have to rely on system calls and have a binary for Linux. Is there a library that does it for Perl or some other language?
What's the best way of doing this?
I know nothing about RIFF files or their structure, uses, etc. But did you try searching CPAN? The first result looks pretty promising.
The website I reference had the answer I needed. I didn't know they made a linux variant.
I have the following script for the exact thing you asked about.
#!/bin/bash
echo "$1"
ffmpeg -y -i "$1" -f wav out.wav > /dev/null 2>&1 && \
normalize-audio -q out.wav && \
lame --silent -a -m m --cbr -b 64 -q 0 out.wav out.mp3 && \
ffmpeg -y -i out.mp3 -f wav -acodec copy "$1" > /dev/null 2>&1 && \
echo "done."
rm out.wav out.mp3
Just edit the parameters to lame or just use the ffmpeg call and you're set.