On Thu, Dec 29, 2011 at 07:18:01PM +0000, Matt Burgess wrote: > Hi all, > > I'm looking into ripping my DVD collection into WebM format (VP8 video > via libvpx, and vorbis audio via libvorbis). The following command > works, in that it gives me a suitable quality video with audio in sync: > > ffmpeg -i input.vob -aspect 16:9 -vpre libvpx-720p -aq 5 -f webm -y \ > output.webm > > However, it takes a long time to encode. It averages around 6fps. > Bearing in mind that the source file is 24fps, this means that encoding > takes 4 times as long than actually watching the DVD. > > This may be usual in the video encoding world, but I've only ever had > experience of encoding audio, which typically happens at a faster rate > than it takes to listen to. > > So, I guess my questions are: 1) am I expecting too much, 2) Does other > people's experience match mine or 3) How do I speed this process up? > > Thanks, > > Matt. > Hi Matt,
I've never extracted vob files (for one thing, my current disks are too small - upgrading one machine is planned, but needs new hardware [ old via_sata doesn't do even sata2 ] and there's a shortage of my favourite cheap CPUs at the moment). But, even converting my own short files takes significant cpu cycles (ffmpeg2theora typically takes a bit longer than the playing time, converting short video to other formats can take significantly longer. Transcoding audio can be a lot simpler than transcoding video: in audio, lossy codecs remove things that are supposedly inaudible. In video, the aim is to reduce the bitrate without getting offensive visual disturbance - a lot more data may need to be reviewed. That's why there are the 'Advanced Video Options' listed in the ffmpeg manpage. I'm on a single AMD processor - intel are reputedly better for transcoding, and more CPUs always helps [ you might need to force the desired number of threads, or ffmpeg might do an adequate job out of the box ]. When I was searching for ffmpeg options that might be useful, I found quite a lot of suggestions. As always, the accepted command-line switches, and the defaults, differ across different versions of ffmpeg. Try searching for 'ffmpeg cheat sheet' if you haven't already done that. ĸen -- das eine Mal als Tragödie, das andere Mal als Farce -- http://linuxfromscratch.org/mailman/listinfo/lfs-chat FAQ: http://www.linuxfromscratch.org/faq/ Unsubscribe: See the above information page
