[mythtv] Media monitoring few questions
denis at denix.org
Sun Mar 7 22:21:29 EST 2004
Denys Dmytriyenko wrote:
> I've been playing with mythvideo to solve this problem for some time
> now. Here are my findings:
> 1. It is possible just to have a symbolic link to your cdrom mounting
> point in the directory your video files are. When videotree starts and
> builds a tree of video files, it scans that directory and adds all files
> on CD if it is mounted.
> 2. If you don't use supermount to mount your CDs, mythfrontend has to be
> suid root. The reason is, that kernel cdrom driver only allows root to
> unlock the tray, if it's mounted. That's why you cannot open the tray if
> it is mounted. Doing "chmod +s mythfrontend" solves this. But it may be
> a security risk to run it as root.
> 3. If you use supermount, it is possible to open/close the tray at any
> time you want and a drive stays mounted all the time. Myth's media
> monitor supports supermount with iso9660 filesystem only, but this is
> not the problem. The real problem I've encountered is that it takes 34
> seconds (!) to access /mnt/cdrom mount point if there is no disc in the
> drive. Otherwise accessing /mnt/cdrom takes no time and reflects the
> content of the current disc - i.e. no mount/umount necessary!
> If I'm able to resolve this issue with supermount, it only takes a
> little modification to rebuild a videotree when new disc is inserted and
> everything else is already taken care of!
Replying to myself. From supermount's FAQ:
Q: When I do ls -l /mnt it pauses for some time and LED on CD-ROM start
A: Try sysctl -w dev.cdrom.autoclose=0. Apparently most CD-ROM drives do
not distinguish between NO MEDIA and TRAY OPEN conditions and always
return TRAY OPEN. In return cdrom driver tries to close tray that makes
CD-ROM drive to check for media presence - and that is exactly what is
causing those delays and unwanted drive activity. It was reported that
some drives need very long time to give up. Setting autoclose to 0 makes
cdrom driver to return immediately with ENOMEDIA.
Anyway, here is what I've done to make mythvideo play videos from CD-ROM
(/media/video is where mythvideo looks for files):
# ln -s /mnt/cdrom /media/video
# sysctl -w dev.cdrom.autoclose=0
# grep supermount /etc/fstab
none /mnt/cdrom supermount fs=iso9660,dev=/dev/hdb,ro,user 0 0
Now, I can run mythfrontend as a normal user and be able to change CDs
without mounting/unmounting them and when I enter videotree it scans for
video files on a disc.
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