How to catch FFMPEG Output

Question

5.00/5 (1 vote)

See more:

Hello everybody.
I've tried next lines:

C#

Process p = new Process();
p.StartInfo.UseShellExecute = false;
p.StartInfo.RedirectStandardOutput = true;
p.StartInfo.CreateNoWindow = true;
p.StartInfo.FileName = "ffmpeg";
p.StartInfo.Arguments = " -h ";
p = Process.Start(p.StartInfo);
this.textBox1.Text = p.StandardOutput.ReadToEnd();
this.textBox1.Update();
p.WaitForExit();

In this case everything looks fine and TextBox have got a output of ffmpeg.exe.
But in case of real job:

C#

p.StartInfo.Arguments = " -i input.avi -y output.ts ";

I can see just empty TextBox although convertion has been completed and output.ts has been created.

Thanks in advance.

Posted 11-Nov-12 3:40am

werfog

Updated 11-Nov-12 6:47am

v2

Add a Solution

Comments

Pablo Aliskevicius 11-Nov-12 9:58am

What is the output if you run the command on a console window?
What happens if you call ReadToEnd() again after WaitForExit()?

werfog 11-Nov-12 10:52am

1. I don't know how to add a picture to my reply. The text of console is

C:\Users\ааа\Documents\Visual Studio 2010\Projects\C#\VisualFFmpeg_1\bin\Debug>f
fmpeg.exe -i E:\input.avi -y E:\output.ts
ffmpeg version N-46055-g5f0105b Copyright (c) 2000-2012 the FFmpeg developers
built on Oct 26 2012 17:51:52 with gcc 4.7.2 (GCC)
configuration: --enable-gpl --enable-version3 --disable-pthreads --enable-runt
ime-cpudetect --enable-avisynth --enable-bzlib --enable-frei0r --enable-libass -
-enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libfreetype --enab
le-libgsm --enable-libmp3lame --enable-libnut --enable-libopenjpeg --enable-libo
pus --enable-librtmp --enable-libschroedinger --enable-libspeex --enable-libtheo
ra --enable-libutvideo --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-li
bvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-libxvid --ena
ble-zlib
libavutil 52. 0.100 / 52. 0.100
libavcodec 54. 69.100 / 54. 69.100
libavformat 54. 35.100 / 54. 35.100
libavdevice 54. 3.100 / 54. 3.100
libavfilter 3. 20.106 / 3. 20.106
libswscale 2. 1.101 / 2. 1.101
libswresample 0. 16.100 / 0. 16.100
libpostproc 52. 1.100 / 52. 1.100
Input #0, avi, from 'E:\input.avi':
Metadata:
encoder : Lavf51.12.1
Duration: 00:01:00.13, start: 0.000000, bitrate: 4218 kb/s
Stream #0:0: Video: mpeg4 (Simple Profile) (xvid / 0x64697678), yuv420p, 640
x360 [SAR 1:1 DAR 16:9], 29.97 tbr, 29.97 tbn, 29.97 tbc
Stream #0:1: Audio: mp3 (U[0][0][0] / 0x0055), 44100 Hz, stereo, s16, 128 kb
/s
Output #0, mpegts, to 'E:\output.ts':
Metadata:
encoder : Lavf54.35.100
Stream #0:0: Video: mpeg2video, yuv420p, 640x360 [SAR 1:1 DAR 16:9], q=2-31,
200 kb/s, 90k tbn, 29.97 tbc
Stream #0:1: Audio: mp2, 44100 Hz, stereo, s16, 128 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (mpeg4 -> mpeg2video)
Stream #0:1 -> #0:1 (mp3 -> mp2)
Press [q] to stop, [?] for help
frame= 227 fps=0.0 q=31.0 size= 999kB time=00:00:07.72 bitrate=1059.6kbits/
frame= 476 fps=462 q=31.0 size= 1849kB time=00:00:16.00 bitrate= 946.6kbits/
frame= 742 fps=480 q=31.0 size= 2748kB time=00:00:24.85 bitrate= 905.5kbits/
frame= 1005 fps=488 q=24.8 size= 3648kB time=00:00:33.66 bitrate= 887.8kbits/
frame= 1272 fps=494 q=31.0 size= 4519kB time=00:00:42.56 bitrate= 869.7kbits/
frame= 1526 fps=494 q=31.0 size= 5402kB time=00:00:51.05 bitrate= 866.7kbits/
frame= 1790 fps=497 q=31.0 size= 6295kB time=00:00:59.86 bitrate= 861.5kbits/
frame= 1800 fps=497 q=31.0 Lsize= 6339kB time=00:01:00.12 bitrate= 863.7kbits
/s
video:4708kB audio:940kB subtitle:0 global headers:0kB muxing overhead 12.233324
%

C:\Users\ааа\Documents\Visual Studio 2010\Projects\C#\VisualFFmpeg_1\bin\Debug>p
ause
Для продолжения нажмите любую клавишу . . .

2. Nothing is shown again in the TextBox.
Thanks for your attention.

Pablo Aliskevicius 12-Nov-12 4:21am

My guess is that there is some kind of race condition: ReadToEnd() may get called before ffmpeg writes to the standard output. But, it's just a guess...
I've upvoted the question in the hope of luring someone who knows better.
Best wishes,
Pablo.

werfog 12-Nov-12 6:43am

Thank you very much.
I wrote that in the hope that someone who encoutered such a problem and solved that could help.
I'm trying to sort out that trouble. And I suspect that answer lies somewhere in Apartment Threading. But it's hard to understand for me.

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

werfog · Accepted Answer · 2012-11-13T03:36:00

The best and the shortest solution was found in the article
' Video Transcoding "YouTube-Style" with ffmpeg ' posted by Jonathan Lathigee.
Video Transcoding "YouTube-Style" with ffmpeg
He writes:
"Another problem came in the capturing of output from FFMPEG to get all of the file's metadata. I created a new process and streamReader, and captured the StandardOutput from the process. Nothing. Turns out that there is no specific command in FFMPEG to read metadata from a video file, instead this info comes out as a StandardError stream when FFMPEG is called with no output file specified. Once I switched from capturing the StandardOutput to StandardError, I had no problems."

And that was key factor for me. As I tried to catch StandardOutput of ffmpeg instead of catching StandardError. So I got all necessary lines into my TextBox. Finally I used asynchronous reading that was more suitable for my purpose. Here is the code.

C#

try
            {
                Process p = this.process1;
                String input = " -i " + this.listBox2.Text; //  /c ffmpeg.exe // for launching ffmpeg via cmd.exe
                String size = " -s " + this.comboBox1.Text;
                String codec = " -vcodec " + this.comboBox2.Text;
                String encoder = " -vtag " + this.comboBox3.Text;
                String quality = " -qscale " + this.comboBox4.Text;
                String videobr = " -b:v " + this.comboBox4.Text + "k";
                String audiobr = " -ab " + this.comboBox5.Text + "k";
                String output = " -y " + this.textBox2.Text;
                String report = " 2> \"" + this.textBox2.Text + ".log\""; // for launching ffmpeg via cmd.exe and putting output into file
                String s = input + size + codec + encoder + videobr + audiobr + output;// +report;
                String sa = " -h ";// help from ffmpeg
                p.StartInfo.Arguments = s;
                p.Start();

                p.BeginOutputReadLine();
                p.BeginErrorReadLine();
                MessageBox.Show("Waiting for the process to exit....");
                //p.WaitForExit();
                if (p.HasExited) { p.CancelErrorRead(); p.CancelOutputRead(); p.Close(); MessageBox.Show("Closed"); }
            }
            catch (Exception ex)
            {
                MessageBox.Show("1.\n"+ex.Message);
            }

Following ErrorDataReceived handler.

C#

private void process1_ErrorDataReceived(object sender, DataReceivedEventArgs e)
        {
            this.textBox1.Text += e.Data;
            this.textBox1.Update();
            //MessageBox.Show("4.Error\n" + e.Data);
        }

You can find some extra lines: MessageBoxes etc. they are just for debugging.
So Great Thanks to Jonathan Lathigee and 5 stars for him.
I'm glad if my experience is usefull for you.
Best wishes.