setComplexVideoFilter with unexpected results with filtergraph

[igracia]

I'm using the setComplexVideoFilter to add an adelay/amix filter, to merge audio and video tracks that have different lengths, into a single file. I have ffmpeg 3.2 installed in OS X.

The actual command that works is
ffmpeg -y -v error -i video.trk -i audio.trk -filter_complex "[1:0]adelay=10000|10000[t1];[t1]amix=inputs=1" -c:v copy out.webm. To have the library generating the same command, I had to add escaped quotes to the string, producing the following line outputBuilder.setComplexVideoFilter("\"[1:0]adelay=10000|10000[t1];[t1]amix=inputs=1\"");. This yields the following result.

/usr/local/bin/ffmpeg -y -v error -i video.trk -i audio.trk -filter_complex "[1:0]adelay=10000|10000[t1];[t1]amix=inputs=1" -c:v copy out.webm
Truncating packet of size 21863284 to 2742585
Truncating packet of size 21863284 to 181769
[AVFilterGraph @ 0x7faa89416fe0] No such filter: '"'
Error initializing complex filters.
Invalid argument

Issuing the following line outputBuilder.setComplexVideoFilter("[1:0]adelay=10000|10000[t1];[t1]amix=inputs=1"); produces an expected error, as the complex filter should go between quotes

/usr/local/bin/ffmpeg -y -v error -i video.trk -i audio.trk -filter_complex [1:0]adelay=10000|10000[t1];[t1]amix=inputs=1 -c:v copy out.webm
Truncating packet of size 21863284 to 2742585
Truncating packet of size 21863284 to 181769
Filter amix has an unconnected output

which is expected, as it is the same output that you get when running from command line.

Not sure if there's anything we can do here, and is a problem from the ProcessBuilder itself. Any ideas?

[igracia]

@bramp Could this be related with #76?

[igracia]

More failed tests with similar results

• [1:0]adelay=10000[t1];[t1]amix=inputs=1 (remove the pipe |)
• [1:0]adelay=10000[t1],[t1]amix=inputs=1 (replace the semicolon ;)

The last filter would allow us to run from the command line as ffmpeg -y -v error -i video.trk -i audio.trk -filter_complex [1:0]adelay=10000[t1],[t1]amix=inputs=1 -c:v copy out.webm, but both produce wrong output when run from a Java program.

[igracia]

It seems like it is related to how ProcessBuilder handles those args, and the fact that certain args have to be escaped. I've managed to get it working with this workaround

ffmpeg = new ProcessBuilder(
                    new String[] { "/bin/sh", "-c", "/usr/local/bin/ffmpeg " + argsStr })
                            .redirectErrorStream(true).start();

Not sure the "/bin/sh" , "-c" is something you want to have there. Should I upload a PR?

[igracia]

@bramp Would you accept a pull request with this modification?

[bramp]

There are a lot of Windows users of this library, so I wouldn't want to put a Linux specific fix in place. I will accept pull requests to fix this in a generic way.

[bramp]

I just read more about the failings in how java handles character escaping. http://bugs.java.com/view_bug.do?bug_id=6468220 and http://bugs.java.com/view_bug.do?bug_id=6518827

It might be worth using https://commons.apache.org/proper/commons-exec/index.html instead of the process builder. Happy to accept that pull request.