OK, this is driving me nuts!

This is the 3rd thread in my series about trying to get gapless audio recording working from the command line...

I'm having troubles with my FIFO buffer...

The Concept: Use arecord to send the raw audio input to a fifo buffer, and encode that raw data using oggenc. In order to split the output files, oggenc restarts periodically with a new filename. While it is restarting, the FIFO buffer is filling with the audio to be encoded once oggenc is running again. Ergo, not a millisecond of audio is missed.

There are 2 Problems with this.
1) arecord starts before oggenc. Therefore when oggenc reads the fifo, it just takes what's there, encodes it and says done. It doesn't keep going and going like if you piped arecord directly to oggenc. If oggenc is started before arecord, then it seem to work fine, however this isn't an option since oggenc has to restart regularly to change filenames, and arecord can not be stopped (otherwise we'll miss audio)
2) The fifo doesn't get emptied when it's read from. Example:
1) Create the fifo
2) Show that it's there and empty
3) Start arecord in the background
4) cat the fifo to a normal file. This should empty the fifo back to 0 bytes.
5) ls shows the nromal file we cat'ed to is 29M, and the fifo has not emptied and grown another 1M

A few things of note here.

1) Your mkfifo appears to have failed. That 'ls -lh /tmp/audio' output should have a 'p' as the first character to denote a pipe, e.g. prw-r--r--. You've been cat'ing a normal file (arecord's probably clobbered the fifo and replaced it with a file).

2) I think you may be misunderstanding what a FIFO is. The 'buffer' is only 4kB long on i386 Linux, and that buffer is just a kernel memory area that makes read-writes more efficient. There's no real buffering going on - named pipes are just a convenient way of doing inter-process communication. No data ever hits the disks.

3) As soon as either end of a pipe is closed, the IPC is torn down for everything in the pipe. There's no way to 'reconnect' to a pipe once it's closed.

Dave

Think I might have a better idea, though.

Install the 'ogmtools' package, if you don't already have it.

$ mkfifo /tmp/pipe.ogg
$ ogmsplit <options> /tmp/pipe.ogg &
$ arecord <options> | oggenc <options> > /tmp/pipe.ogg

This will record and encode into the /tmp/pipe.ogg FIFO, and the resulting ogg stream will be split by 'ogmsplit' into seperate files.

Not tried it myself, but should hopefully do what's needed. Only problem might be if ogmsplit needs to rewind through the input file, to get a previous frame or something.

Dave

Closing the loop on this extremely old problem... I finally found a turnkey solution in LiquidSoap (http://savonet.sourceforge.net/). There is also rotter (https://www.aelius.com/njh/rotter/)