Hi all,
I have this little sh script which saves an ogg audio stream,
streamed by an internet radio. It's short enough to quote it:
--- cut --
#!/bin/sh
# $1 is length in seconds, $2 is the output filename.
# The stream itself is prefixed by a HTTP header, which needs to be
# trimmed off up to (and not including) the ^OggS
# HTTP/1.0 200 OK
# Content-Type: application/ogg
# icy-br:128
# icy-description:European-style cultural station
# icy-genre:classical
# icy-name:CRo3 - Vltava
# icy-pub:1
# Server: Icecast 2.2.0
#
# OggS......
if test $# -lt 2 ; then
echo "usage: $0 length output" 2>&1
exit 1
fi
NC=`which nc` 2>/dev/null
test -x $NC || exit 1
HOST="amp1.cesnet.cz"
FILE="cro3.ogg"
PORT="8000"
LENGTH="$1"
OUTPUT="$2"
STREAM="/tmp/vltava.$$"
test -e $OUTPUT && { echo "$OUTPUT already exists" >&2 ; exit 1 ; }
mkfifo $STREAM || { echo "Cannot create output stream $STREAM" >&2; exit 1; }
sed -n -e '/^OggS/,$ p' < $STREAM > $OUTPUT &
{ echo "GET /$FILE HTTP/1.0" ; echo ; } \
| $NC $HOST $PORT > $STREAM &
PID=$! && sleep $LENGTH && kill $PID
rm -f $STREAM
echo "Recorded $LENGTH seconds of http://$HOST:$PORT/$FILE";
echo "into $OUTPUT"
--- cut --
The idea is that the stream is just dumped by nc(1) to a fifo,
from which a sed one-liner copies everything starting with the
^OggS header (so that we trim off the HTTP header).
I run this script from cron, obviously, as in
05 00 * * 7 $HOME/bin/vltava 5100 $HOME/vltava/`date +\%Y\%m\%d`-jazzclub.ogg
Now, *sometimes* (I know) the script results in cron saying
/home/hans/bin/vltava[43]: kill: 15062: No such process
Recorded 5100 seconds of http://amp1.cesnet.cz:8000/cro3.ogg
into /home/hans/vltava/20061024-jazzclub.ogg
*Usually* (I know) it finishes OK, and the *ogg is a valid ogg stream.
In this failing case, it *also* is a valid ogg stream, but much
shorter than usual.
So I suppose the background nc dies before I try to kill it myself
(that is, after sleeping for $LENGTH seconds).
One reason for this to happen is that the ogg being streamed out just
finishes before $LENGTH (a special case being it returns immediately,
possibly getting a HTTP error and an immediate EOF. But I doubt that
- it's a continuously streamed radio station). Or the running nc(1)
loses connection?
Or maybe the inner structure of live-streamed OGG's is such that the
(in fact) HTTP response is EOFed when one show finishes and another
starts?
Or, obviously, my script is somehow wrong - any hints?
Sorry if this is trivial.
Thanks for your time
Jan
