On Thu, 2008-02-07 at 22:32 -0600, Carl Karsten wrote: > Looking at the example, I gotta ask how sane it is. [...] > > for reference, here are the man page descriptions: > ========== > transcode -x v4l,null --use_rgb -i /dev/video -f 3 -g 1600x1200 -y raw,null > -z > -r 2 -f 10 -o test.avi [...] > ========== > I got a few questions... > Why --use_rgb ? (guessing the answer is: device dependent, ask the > manufacture.)
Yes :) (Analog) screens work in RGB colorspace, so it sounds pretty natural for a frame grabber to output pictures in that way. > Do I need to specify a fps and resolution, or can transcode detect it? Transcode should be able to autodetect, but doing it correctly vastly depends on v4l video driver: it should report informations correctly (and unfortunately this is not always trivially true...) > -f 3 -f 10 Why are there 2? Typo? > -z Why doesn't their driver do that? I don't know. > -y raw - Is that pass through, or does it decompress the mpeg into a hard > drive > eating machine? I want to minimize lossy compression until it is edited, but > I > will be recording 8 hours at a shot. (maybe only 4, then swap HD's) -y raw just skip the video compression step on export. If input is already compressed, we're fine; otherwise, this will eat tons of gigs (see the resolution!) > -r 2 I don't want to reduce anything. I can just take that out, right? Yes > (wondering why they added parameters that are counter productive.) > > -o test.avi If the stream is mpeg, shouldn't I name the file .mpeg? I guess this frame grabber spit out raw frames, not mpeg-compressed ones. > And just for added noise, here are the mplayer examples: > > mplayer -tv driver=v4l:outfmt=rgb24 -flip tv:// > > mencoder \ > -oac lavc \ > -ovc lavc \ > -lavcopts vcodec=mpeg4:keyint=100:vbitrate=8000:vhq \ > -noaspect -flip \ > -o test.avi \ > -tv noaudio:driver=v4l:outfmt=bgr24:device=/dev/video0 \ > tv:// This command line suggests as well that this frame grabber produces raw, uncompressed frames. The two command lines sound inconsistent :\ Bests, -- Francesco Romani // Ikitt [ Out of memory. ~ We wish to hold the whole sky, ~ But we never will. ]
