How to store file in ffmpeg

waqasdaar · 01-20-2009, 04:39 PM

I am running this command but I am unable to store a file contents. I dont know where is the problem, I am stuck on this from last 3 days. so now I decided to post on forum.

PHP Code:


			
ffmpeg -re -i movie.mpg -vcodec mpeg4 -an -f rtp rtp://x.x.x.x:123456 -vn -acodec mp2 -f rtp rtp://x.x.x.x:44444 -newaudio 2>/dev/null 1>/tmp/tmp_sdp&

 

head -n14 /tmp/tmp_sdp | tail -n13 > /home/jhon/movie.sdp

ffmpeg redirect the output successfully to the /tmp/tmp_sdp file, but when I tried to read the contents in script it is blank. But when I issued this command in Bash shell It prints all required values.

If you have any idea then please post some solution.

Thanks in Advanced

colucix · 01-20-2009, 04:45 PM

I think ffmpeg write messages to standard error instead of standard output. This is because of the ability to stream output to stdout if you use - as the output filename. Have you tried to substitute 2>/dev/null 1>/tmp/tmp_sdp with simply 2>/tmp/tmp_sdp?

waqasdaar · 01-20-2009, 04:57 PM

yes I have tired, but no success. Becuase ffmpeg use 2 as a stderr and 1 as stdout and therefor I redirect all error to /dev/null and I only want the output of this command. thatshwy I redirect it to temp file which I want to use it for process but I am not able to 'cat' this file contents to any other file it. Even when I tried to cat tmp file it shows me all the contents but when I tried to use this same command which I run in the Bash Shell succesfuly shows me blank result. I dont know what is the problem. Hope you gave me better suggestion.

colucix · 01-20-2009, 05:17 PM

Sorry but I don't understand. Look at the following example:

Code:

$ ffmpeg -i "movie.mpg" -vcodec mpeg4 movie.avi > ./ffmpeg.log
<output displayed here>
<output displayed here>
<omitted>
$ ls -l
-rw-r--r-- 1 colucix users        0 2009-01-21 00:06 ffmpeg.log
-rw-r--r-- 1 colucix users 58653112 2008-12-28 21:53 movie.mpg
-rw-r--r-- 1 colucix users 13275710 2009-01-21 00:07 movie.avi
$ ffmpeg -i "movie.mpg" -vcodec mpeg4 movie.avi 2> ./ffmpeg.log
$ ls -l
-rw-r--r-- 1 colucix users     6413 2009-01-21 00:08 ffmpeg.log
-rw-r--r-- 1 colucix users 58653112 2008-12-28 21:53 movie.mpg
-rw-r--r-- 1 colucix users 13275710 2009-01-21 00:09 movie.avi

As you can see if I redirect just the standard output (first ffmpeg command), the messages appear on the screen but not in the log file. If I redirect just the standard error (second ffmpeg command) nothing is displayed on the screen and the output goes to the log file. To me this demonstrates that ffmpeg writes to standard error and if you redirect it to /dev/null you will not get any message.

You can also investigate on the -passlogfile option of ffmpeg to see if it is useful for your issue.

waqasdaar · 01-20-2009, 05:37 PM

I know all these stuff man. have you tried the command which I posted above. Then you understand what I am trying to say. The command which I posted above displayed generates a SDP information If I dont redirect the 1 to File it displays to stdout. I need this information so I redirect to a file. Then I have to delete one line from this File, but I am unable to do so.

colucix · 01-20-2009, 05:43 PM

Ok. It's clear now. I just didn't know the rtp:// protocol. Sorry.

waqasdaar · 01-20-2009, 05:47 PM

Thanks for all your help.
Hope some one knows the answer of my question.

colucix · 01-20-2009, 06:18 PM

Here I am again! I will be your nightmare... just for the next couple of minutes!

Seriously, to me since you launch the ffmpeg command in background, the head/tail command is executed immediately after, so that the ffmpeg command has not the time to populate the /tmp/tmp_sdp file. Take in mind that when you issue a redirection the output file is immediately created and has 0 size. Solution: insert a sleep 5 between the ffmpeg line and the head/tail line.

waqasdaar · 01-20-2009, 07:02 PM

Thanks a lot Man.
now I got your point. Its working now.
Thank you very much