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#11 LVM HOWTO, mplayer man page, & FOSS resources Posted by undefined (192.91.xx.xx) on Wed 23 Apr 2008 at 22:54 if this article was a comment on slashdot, i would moderate it "redundant". if this comment was on slashdot, i might moderate it as "flamebait". one document is sufficient for LVM: the "LVM HOWTO". it describes "logical volume management", the benefits of LVM on both large and small systems, introduces the components of LVM (PV, VG, LV, etc), gives example command-line usage, and even has "recipes" (series of commands to perform complex, but common, tasks). maybe this complaint about LVM was warranted in 2002 when i used woody to create a root-on-lvm setup (which required installing a "base" system to a small partition, partitioning the rest of the drive, creating desired PVs, VGs, & LVs, formating LVs, copying parts of the "base" system to the proper LVs, praying & rebooting). now even the infamous debian installer handles it. back then you had to inevitably hand-tweak some mkinitrd script posted by another user of your distro to the LVM mailing list; none of this hold-your-hand-do-it-all-for-you mkinitramfs. okay, enough of the "old man" talk. about mplayer's man page: the problem there isn't lack of information, but too much information. search the man page long enough for "jpeg" and you'll find an entry under "video output drivers" about JPEG that says "Output each frame into a JPEG file in the current directory." so next i need to find the option to specify a frame. searching for "frame" i eventually stumble upon the "-frames" option, but since that only specifies how many frames to decode, i need to tell it where to start. searching for "start" didn't turn up anything, so i try "seek" (because skipping through a media file, which is what i want mplayer to do to get to the desired frame, is called "seeking"). searching for "seek" i found the "-ss" option which is time based, but how many users measure absolute position within a media stream in frames instead of time, so its good enough for me (and i can always have mplayer seek to a particular time and dump several frames with the previously discovered "-frames" option. if you really want the 3000th frame, then use "-frames 3000" and delete the first 2999 JPEG files. or you can just search for "mplayer output image frame" (a keyword abbreviation of "i want mplayer to output an image from a frame") with a hit in the top 10 that mentions what i want but using a .net wrapper. i refine my searching using vocabulary from that page ("mplayer extract frame") and the first hit does what i want (but using time-offsets, not frame-offsets, which further reinforces what i previously said). either method required about 10 minutes of searching and reading. it took me longer to repeat and document the process here than to actually execute it the first time (which probably explains why free software developers have an aversion to writing documentation ;-). maybe 10 years ago complaining about documentation on common free software was valid, but now the community is so large that just about anything i want to know or do i can find in project websites, wikipedia, blogs, forums, or mailing list archives using google (and maybe a little search kung-fu). this brings me to a funny realization: people think of the linux early adopters as "hackers", and "hackers" are characterized as being anti-social, but in the early days you had to interact with people (mailing lists, irc, usenet, user groups) to learn anything. now days you can learn linux while truly being anti-social, needing only to interact with google, due to the wealth of online material.
if this article was a comment on slashdot, i would moderate it "redundant". if this comment was on slashdot, i might moderate it as "flamebait".
one document is sufficient for LVM: the "LVM HOWTO".
it describes "logical volume management", the benefits of LVM on both large and small systems, introduces the components of LVM (PV, VG, LV, etc), gives example command-line usage, and even has "recipes" (series of commands to perform complex, but common, tasks).
maybe this complaint about LVM was warranted in 2002 when i used woody to create a root-on-lvm setup (which required installing a "base" system to a small partition, partitioning the rest of the drive, creating desired PVs, VGs, & LVs, formating LVs, copying parts of the "base" system to the proper LVs, praying & rebooting). now even the infamous debian installer handles it. back then you had to inevitably hand-tweak some mkinitrd script posted by another user of your distro to the LVM mailing list; none of this hold-your-hand-do-it-all-for-you mkinitramfs. okay, enough of the "old man" talk.
about mplayer's man page: the problem there isn't lack of information, but too much information. search the man page long enough for "jpeg" and you'll find an entry under "video output drivers" about JPEG that says "Output each frame into a JPEG file in the current directory." so next i need to find the option to specify a frame. searching for "frame" i eventually stumble upon the "-frames" option, but since that only specifies how many frames to decode, i need to tell it where to start. searching for "start" didn't turn up anything, so i try "seek" (because skipping through a media file, which is what i want mplayer to do to get to the desired frame, is called "seeking"). searching for "seek" i found the "-ss" option which is time based, but how many users measure absolute position within a media stream in frames instead of time, so its good enough for me (and i can always have mplayer seek to a particular time and dump several frames with the previously discovered "-frames" option. if you really want the 3000th frame, then use "-frames 3000" and delete the first 2999 JPEG files.
or you can just search for "mplayer output image frame" (a keyword abbreviation of "i want mplayer to output an image from a frame") with a hit in the top 10 that mentions what i want but using a .net wrapper. i refine my searching using vocabulary from that page ("mplayer extract frame") and the first hit does what i want (but using time-offsets, not frame-offsets, which further reinforces what i previously said).
either method required about 10 minutes of searching and reading. it took me longer to repeat and document the process here than to actually execute it the first time (which probably explains why free software developers have an aversion to writing documentation ;-).
maybe 10 years ago complaining about documentation on common free software was valid, but now the community is so large that just about anything i want to know or do i can find in project websites, wikipedia, blogs, forums, or mailing list archives using google (and maybe a little search kung-fu).
this brings me to a funny realization: people think of the linux early adopters as "hackers", and "hackers" are characterized as being anti-social, but in the early days you had to interact with people (mailing lists, irc, usenet, user groups) to learn anything. now days you can learn linux while truly being anti-social, needing only to interact with google, due to the wealth of online material.
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