mjhjmtu

I'm using a program which continuously writes MPEG-TS video data to a file while it's running. I'm expecting it to run continuously for many days.

I want to use ffmpeg to transcode this video data live. So that the .mts file doesn't grow continuously until I run out of hard drive space, I'm trying to get the first program to write to a named pipe and for ffmpeg to read from that pipe.

I tried doing ffmpeg -i /tmp/test.mts -c:v libx264 test.mp4 but it seems that ffmpeg quits once it reaches the end of the pipe, instead of waiting for new data. For example if I start the program, wait 30 seconds and then run ffmpeg, I'll only get ~50 seconds of video out. (30 seconds + the time it takes ffmpeg to catch up)

I have managed to get it working by doing ffmpeg -i pipe:0 -c:v libx264 test.mp4 < /tmp/test.mts but this feels kind of hacky to me, using stdin to do this. Is there a way I can directly provide the named pipe as an input to ffmpeg and have it wait for new data once it reaches the end of the current data?

Thanks!

Simply open that fifo for writing (and keep it open) from another place, too. Example:

In a window:

mkfifo /tmp/test.mts
exec 7<>/tmp/test.mts
ffmpeg -i /tmp/test.mts out.mp4

In another window:

cat ... >/tmp/test.mts
cat ... >/tmp/test.mts

The idea is that a reader won't receive an EOF from a pipe until all processes which had it open for writing have closed it:

$ mkfifo /tmp/fifo
$ cat /tmp/fifo &
[1] 26437
$ exec 7>/tmp/fifo
$ echo yes >/tmp/fifo
yes
$ echo yes >/tmp/fifo
yes
$ echo yes >/tmp/fifo
yes
$ exec 7>&-
$
[1]+ Done cat /tmp/fifo

Without the exec 7>/tmp/fifo which keeps an open handle to the writing end of /tmp/fifo, the cat would've terminated after the first echo.