[FFmpeg-user] FFMPEG output to append to a text file without overwriting the content

[DopeLabs]

you can always just timestamp each text file so it writes a new file on each iteration of ffmpeg running

out.mp4 2> $(date +%Y-%m-%d_%H-%M-%S).txt



> On Jun 4, 2018, at 5:48 57PM, Sana Tafleen <sana.tafleen at gmail.com> wrote:
> 
> What I am trying to achieve here is to get the number of I,P and B frames
> at the end of streaming. When the disconnection happens, the ffmpeg process
> at the sender stops at the terminal and when I connect it back, it starts
> sending the frames. Doing this, the number of frames at the receiver is
> higher than the number of frames at the sender. I am guessing it is
> because, when the ffmpeg stops, it kills the previous process and starts a
> new process trying to gain connection with the destination. When it gets
> the connection, a new process starts and that output is sent to 'out.txt',
> overwriting the output of the previous ffmpeg process. Which is why the
> frame count at sender is lesser than that at the receiver. I hope this
> makes any sense. Any help here would be appreciated.
> 
> 
> Regards,
> Sana Tafleen
> 
> On Mon, Jun 4, 2018 at 7:36 PM, robertlazarski <robertlazarski at gmail.com>
> wrote:
> 
>> On Mon, Jun 4, 2018 at 6:06 PM, Sana Tafleen <sana.tafleen at gmail.com>
>> wrote:
>> 
>>> Hello,
>>> 
>>> I am sending a UDP stream to the destination and saving the contents of
>> the
>>> FFMPEG output to a text file. I run the ffmpeg command in a loop as
>>> follows,
>>> 
>>> 
>>> while :
>>> do
>>>      echo `ffmpeg -hide_banner -f v4l2 -i /dev/video0 -c:v libx264 -f
>>> mpegts tcp://ip:port -c:v libx264 /path/to/.mp4 2> out.txt -y`
>>> done
>>> 
>>> 
>>> 
>>> When I disconnect the cable connected the destination, the above ffmpeg
>>> process stops and a new one starts oevrwriting the content of the output
>>> that has been saved. And when I reconnect the cable, a new ffmpeg process
>>> starts and its output is what is displayed in the out.txt file.
>>> 
>>> I need the output of each ffmpeg process that runs to an output file. Can
>>> anyone please suggest me a way to do it?
>>> 
>> 
>> This part of the command, '2> out.txt ' says (a) redirect stderr and not
>> stdout, to out.txt. And (b) overwrite the previous contents.
>> 
>> You can append instead of overwrite by using '2>> out.txt ' .
>> 
>> I would not expect ffmpeg to create a new process in that loop but I have
>> no experience with mpegts. I would try -stdin since I have seen unexpected
>> behavior without it in loops.
>> 
>> A long shot would be using nohup, if its a hangup of some sort. I would try
>> that if I was still stuck. Then strace on the command to see why it was
>> creating the extra process.
>> 
>> Kind regards,
>> Robert
>> 
>> 
>> 
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