How to find mkv files; convert to mp4 with ffmpeg

daweefolk · 04-16-2018, 02:58 PM

I'm not a complete newbie to linux, but here's my problem:
I'm trying to write a script that would use ffmpeg to convert mkv or avi files in a specific directory (and subdirectories) to .mp4.

I know I'll need the ffmpeg line

Code:

(ffmpeg -i filename.mkv -c:v libx264 -maxrate 8M -bufsize 1M filename.mp4)

and likely a 'find' command

Code:

(find /home/daweefolk/Movies -name "*.mkv"?)

but don't know how to hook them together, or if they're even right.

I just want the file converted, with the extension changed but basename the same, in the same directory.

Can I get some help with putting the script together? I plan to set it up in cron to run automatically

teckk · 04-16-2018, 03:10 PM

These files are in the same directory?

Examples:

Code:

for i in *; do
    ffmpeg -i "$i" <options here> ${i%.*}.mp4
done

If they use codecs that can be put into a .mp4 container, and you don't want to reencode

Code:

ffmpeg -i file.mkv -c:a copy -c:v copy ouput.mp4

Quote:

I just want the file converted, with the extension changed but basename the same, in the same directory.

Get the basename for files in dir

Code:

for i in *; do echo ${i%.*}; done

daweefolk · 04-16-2018, 03:41 PM

Quote:

Originally Posted by teckk

These files are in the same directory?

Examples:

Code:

for i in *; do
    ffmpeg -i "$i" <options here> ${i%.*}.mp4
done

If they use codecs that can be put into a .mp4 container, and you don't want to reencode

Code:

ffmpeg -i file.mkv -c:a copy -c:v copy ouput.mp4

Get the basename for files in dir

Code:

for i in *; do echo ${i%.*}; done

As I plan to run this from cron, I was hoping to get a script that would start in my ~/Movies directory and recurse

ondoho · 04-17-2018, 01:19 AM

well be aware that you should run your script as a normal user, not root!

anyhow, a quick change to the previous:

Code:

find ~/Movies -iname '*.mkv' | while read line
do
    ffmpeg -i "$line" ...
    etc....
done

ondoho · 04-17-2018, 01:20 AM

well be aware that you should run your script as a normal user, not root!

anyhow, a quick change to the previous:

Code:

find ~/Movies -iname '*.mkv' | while read line
do
    ffmpeg -i "$line" ...
    etc....
done

Prehistorik · 04-19-2018, 04:22 PM

If you're going to use cron, then there are some other things to consider:

1. Cron limits $PATH to /(s)bin and /usr/(s)bin, so you'll have to use full path to ffmpeg if you have compiled it from source

2. The script must check if the output file already exists and skip the input if it does. Otherwise all files will be encoded over and over again on every run.

You can use a simple file test:

Code:

if [ ! -e "$dest_file" ]; then
    # ... process the file
fi

Or, if source files can change and destinations must be updated:

Code:

if [ ! -e "$dest_file" -o "$src_file" -nt "$dest_file" ]; then
    # ... process the file
fi

3. Encoding is a time-consuming process so if there are many files to encode the previous batch might not be complete yet when the next one starts. I would suggest using some queueing mechanism like Task Spooler (ts):

http://vicerveza.homeunix.net/~viric/soft/ts/

This utility should be in most major distributions. In some cases it can be called a different name like "tsp".

It can also run multiple tasks in parallel, you can set maximum number of simultaneous processes with a command line option.