# Monitoring process of ffmpeg in processing
**URL:** https://discourse.processing.org/t/monitoring-process-of-ffmpeg-in-processing/17950
**Category:** Coding Questions
**Created:** [February 20, 2020, 9:08am UTC](https://discourse.processing.org/t/monitoring-process-of-ffmpeg-in-processing/17950 "2020-02-20T09:08:13Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@tribblesontoast](https://discourse.processing.org/u/tribblesontoast)
#### Post date: [February 20, 2020, 9:08am UTC](https://discourse.processing.org/t/monitoring-process-of-ffmpeg-in-processing/17950/1 "2020-02-20T09:08:13Z")
Hi all,
I’m using ffmpeg to output audio tracks from videos using the example by Hamoid found [here](https://github.com/hamoid/Fun-Programming/blob/master/processing/ideas/2017/05/extractAudioWithFfmpeg/extractAudioWithFfmpeg.pde) but slightly modified (code below).
What I would like to do is to pipe the progress from ffmpeg back into processing so I can visualise it.
Is there any way to do this?
Any help much appreciated.
Thanks.
```auto
//ExtractAudioWithFFmpeg by Hamoid:
//https://github.com/hamoid/Fun-Programming/tree/master/processing/ideas/2017/05/extractAudioWithFfmpeg
import java.io.InputStreamReader;
import java.io.FilenameFilter;
import java.util.*;
import java.util.Arrays;
String path, fileName, ffmpegPath;
boolean saved = false;
void setup() {
// Create data folder if it doesn't exist
(new File(dataPath(""))).mkdirs();
String temp[] = loadStrings("ffmpegPath/ffmpegPath.txt");
ffmpegPath = temp[1];
}
void saveAudio() {
saved = true;
try {
String[] commands = {
ffmpegPath, //use location from videoExport settings.json
"-i",
path, //use location from folderSelected
dataPath(fileName + "_audio.mp3") //use fileName from fileSelected dialog
};
Process proc = exec(commands);
}
catch(Exception e) {
println(e);
}
}
void fileSelected(File selection) {
if (selection == null) {
println("Window was closed or the user hit cancel.");
} else {
path = selection.getAbsolutePath();
println(path);
fileName = path;
fileName = cleanFileName(fileName);
println(fileName);
}
}
String cleanFileName(String unclean) {
//https://forum.processing.org/two/discussion/16801/is-there-a-way-to-check-what-system-a-processing-sketch-is-running-on
String[] list;
char delim = '\\';
list = split(unclean, delim);
int arrayPos = list.length-1;
return list[arrayPos];
}
void draw() {
if (path != null && fileName != null && !saved) saveAudio();
if (saved && frameCount % 60 == 0) exit();
}
void mousePressed() {
println("mouse button pressed: " + mouseButton);
selectInput("select movie to extract audio from:", "fileSelected");
}
```
---
### Author:  [@tribblesontoast](https://discourse.processing.org/u/tribblesontoast)
#### Post date: [February 21, 2020, 11:15am UTC](https://discourse.processing.org/t/monitoring-process-of-ffmpeg-in-processing/17950/2 "2020-02-21T11:15:21Z")
Would I need to so something with stdout or stdin?
[This](https://www.codeproject.com/questions/492381/startinfo-redirectstandardoutp#ctl00_ctl00_MC_AMC_Answers_ctl00_A_Title) seems to suggest that stderr might be the way forward but the method they use to get the error doesn’t exist in processing.
Has anyone done this or have any knowledge they can share?
any and all advice appreciated,
thanks,
Toast
---
### Author:  [@tribblesontoast](https://discourse.processing.org/u/tribblesontoast)
#### Post date: [February 23, 2020, 12:36am UTC](https://discourse.processing.org/t/monitoring-process-of-ffmpeg-in-processing/17950/3 "2020-02-23T00:36:17Z")
So upon second look at Hamoids’ example I saw that he was getting the stdInput and stdError using the code below.
I’ve tried it and i get nothing at all once it prints the “# command output”, not even empty lines.
I’m pretty sure this is what i need, it just doesn’t work.
Any ideas?
@hamoid, are you kicking about?
Thanks,
Toast
```auto
BufferedReader stdInput = new BufferedReader(new
InputStreamReader(proc.getInputStream()));
BufferedReader stdError = new BufferedReader(new
InputStreamReader(proc.getErrorStream()));
println("# Command output");
String s = null;
while ((s = stdInput.readLine()) != null) {
println(s);
}
println("# Command errors");
while ((s = stdError.readLine()) != null) {
println(s);
}
}
```
---
### Author:  [@jeremydouglass](https://discourse.processing.org/u/jeremydouglass)
#### Post date: [February 23, 2020, 4:51am UTC](https://discourse.processing.org/t/monitoring-process-of-ffmpeg-in-processing/17950/4 "2020-02-23T04:51:28Z")
One pattern is logging. Have your process (ffmpeg, whatever) write and flush to a log file. Have your Processing sketch periodically check the file and react accordingly.
What does the ffmpeg output look like, and how are you using it? Is this a progress bar, or are you parsing output messages…?
---
### Author:  [@hamoid](https://discourse.processing.org/u/hamoid)
#### Post date: [February 23, 2020, 5:04pm UTC](https://discourse.processing.org/t/monitoring-process-of-ffmpeg-in-processing/17950/5 "2020-02-23T17:04:23Z")
Hi! To show ffmpeg progress you can do this:
- When you run ffmpeg, add `-report` as an argument. This will create a `.log` file in the same folder, the name in `program-YYYYMMDD-HHMMSS.log` format.
- Your program could scan for the most recent `.log` file and read that file every second.
- In the beginning of that file you could parse the **Duration** of the file
```auto
Input #0, avi, from 'a_movie.avi':
Duration: 00:48:17.00, start: 0.000000, bitrate: 2028 kb/s
Stream #0:0, 41, 1/25: Video: mpeg4, 1 reference frame (DX50 / 0x30355844), yuv420p(left), 688x384 [SAR 1:1 DAR 43:24], 1828 kb/s, 25 fps, 25 tbr, 25 tbn, 30k tbc
Stream #0:1, 49, 1/24000: Audio: ac3 ([0] [0][0] / 0x2000), 48000 Hz, stereo, fltp, 192 kb/s
```
- Below in the log file you will find lines like this
```auto
size= 2048kB time=00:02:17.68 bitrate= 121.8kbits/s speed=39.3x
```
you can compare that **Time** to the **Duration** to calculate the percentage. Then show that percentage in Processing.
To have a predictable log filename (instead of the auto generated with date and time) you can use environment variables or redirecting the output: [https://stackoverflow.com/questions/11241878/ffmpeg-set-report-log-filename](https://stackoverflow.com/questions/11241878/ffmpeg-set-report-log-filename)
See the ffmpeg docs (search for -report): [https://ffmpeg.org/ffmpeg.html](https://ffmpeg.org/ffmpeg.html)
Maybe find ideas at: [https://stackoverflow.com/questions/747982/can-ffmpeg-show-a-progress-bar](https://stackoverflow.com/questions/747982/can-ffmpeg-show-a-progress-bar)
---
### Author:  [@tribblesontoast](https://discourse.processing.org/u/tribblesontoast)
#### Post date: [February 23, 2020, 11:25pm UTC](https://discourse.processing.org/t/monitoring-process-of-ffmpeg-in-processing/17950/6 "2020-02-23T23:25:14Z")
Hi Hamoid,
Thanks for the detailed response, really useful.
I tested the log output in powershell (i’m using win 10, should have stated that earlier) and it works perfectly.
However, putting those commands into processing, it only outputs a zero byte mp3 and no log file.
I’m not sure why this doesn’t work as it is the same order as I tested in powershell.
This is how the saveAudio() method now looks:
```auto
void saveAudio() {
saved = true;
String[] commands = {
ffmpegPath,
"-i",
path,
dataPath(fileName + "_audio.mp3"),
"2> ",
fileName + "_Log.txt"
};
Process proc = exec(commands);
}
```
---
### Author:  [@hamoid](https://discourse.processing.org/u/hamoid)
#### Post date: [February 24, 2020, 10:12am UTC](https://discourse.processing.org/t/monitoring-process-of-ffmpeg-in-processing/17950/7 "2020-02-24T10:12:06Z")
You’re welcome 🙂
Could you maybe print `commands` to verify that everything looks correct? Could it be that the paths need to be absolute because the current working directory is different when running Processing?
You could also use `ProcessBuilder` instead of `exec` which is what I use in the VideoExportLibrary. There I use `redirectOutput` with `ffmpeg` and it logs stuff to a file. See [https://github.com/hamoid/video\_export\_processing/blob/master/src/com/hamoid/VideoExport.java#L632](https://github.com/hamoid/video_export_processing/blob/master/src/com/hamoid/VideoExport.java#L632)
---
### Author:  [@tribblesontoast](https://discourse.processing.org/u/tribblesontoast)
#### Post date: [February 25, 2020, 5:32am UTC](https://discourse.processing.org/t/monitoring-process-of-ffmpeg-in-processing/17950/8 "2020-02-25T05:32:10Z")
Hamoid you champion!
All it took was using processBuilder.
Thanks so much for your help,
Toast
For completeness sake, here’s the saveAudio() method in it’s newly minted state:
```auto
void saveAudio() {
saved = true;
String[] commands = {
ffmpegPath,
"-i",
path,
dataPath(fileName + "_audio.mp3")
};
ProcessBuilder processBuilder = new ProcessBuilder(commands);
Process process;
File ffmpegOutputLog;
processBuilder.redirectErrorStream(true);
ffmpegOutputLog = new File(dataPath(fileName+"_ffmpegLog.txt"));
processBuilder.redirectOutput(ffmpegOutputLog);
processBuilder.redirectInput(ProcessBuilder.Redirect.PIPE);
try {
process = processBuilder.start();
}
catch (Exception e) {
e.printStackTrace();
println(ffmpegOutputLog);
}
}
```