[mythtv] Media monitoring few questions

Xavier Hervy maxpower44 at tiscali.fr
Mon Mar 8 10:11:46 EST 2004

Denys Dmytriyenko wrote:
> 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 
> blinking.
> 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.

Thx for reply.

supermount is what i need but I should patch my kernel (2.4.22 from rh9)
I found kernel patch only for kernel 2.6.2, ss supermount available in 
kernel 2.6.3 without patch ? (it will be my first kernel compile :-[ , 
but i need too bootsplash ;-) )

supermount work too with audio cd / DVD Video / VCD (which don't need to 
be mounted) ?

In my fstab, I found udf type for cdrom can you explain what is udf fs ?

If i understood well, supermount work fine with mediamonitoring ?


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