2011/6/27 Mick <michaelkintz...@gmail.com> > On Monday 27 Jun 2011 12:08:17 Stroller wrote: > > On 26 June 2011, at 19:54, Mick wrote: > > > >> Try passing "-sameq" > > > > > > WOW! Exceptional improvement in a single stroke! Thanks! :) > > > > > > Why is it that ffmpeg degrades the quality with default settings? What > > > does it assume that the setting is? (sorry for the newbie Qs, but this > > > area is until now outside my cognitive map! ;-) > > > > I don't know about the "default" settings, but I would interpret the file > > extension of your original command as telling mplayer that "the > > destination file should be encoded as mpeg2". This is a pretty poor codec > > by today's standards. > > > > I could well be wrong, though. Do you know what format the output file > is? > > No, I have no idea. I assume it is capturing my desktop in some raw video > format - whatever that means. What would X11 feed to x11grab? > > > > IMO you're best encoding to h264 (in an mp4 container) for distribution, > > but I think it's possible the encoding load of that might affect your > > screencast. So you might wish to use sameq or the r210 or rawvideo codecs > > and then transcode to h264 (or WebM or whatever) afterwards. > > I changed the output file to mp4 and it transcodes it accordingly! :) > > ffmpeg -f x11grab -s xga -r 25 -i :0.0 -sameq -aspect 4:3 /tmp/out.mp4 > FFmpeg version SVN-r25767, Copyright (c) 2000-2010 the FFmpeg developers > built on Jan 30 2011 17:04:59 with gcc 4.4.4 > configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64 -- > mandir=/usr/share/man --enable-static --enable-shared --cc=x86_64-pc-linux- > gnu-gcc --enable-gpl --enable-version3 --enable-postproc --enable-avfilter > -- > disable-stripping --disable-debug --disable-doc --disable-network > --disable- > static --disable-vdpau --enable-libmp3lame --enable-libvorbis > --enable-libx264 > --enable-libxvid --enable-libfaac --enable-nonfree --disable-indev=v4l -- > disable-indev=oss --disable-indev=jack --enable-x11grab > --disable-outdev=oss > --enable-libopencore-amrwb --enable-libopencore-amrnb --enable-librtmp -- > disable-altivec --cpu=core2 --enable-hardcoded-tables > libavutil 50.33. 0 / 50.33. 0 > libavcore 0.13. 0 / 0.13. 0 > libavcodec 52.96. 0 / 52.96. 0 > libavformat 52.84. 0 / 52.84. 0 > libavdevice 52. 2. 2 / 52. 2. 2 > libavfilter 1.62. 0 / 1.62. 0 > libswscale 0.12. 0 / 0.12. 0 > libpostproc 51. 2. 0 / 51. 2. 0 > [x11grab @ 0x1a52510] device: :0.0 -> display: :0.0 x: 0 y: 0 width: 1024 > height: 768 > [x11grab @ 0x1a52510] shared memory extension found > [x11grab @ 0x1a52510] Estimating duration from bitrate, this may be > inaccurate > Input #0, x11grab, from ':0.0': > Duration: N/A, start: 1309180986.812527, bitrate: 629145 kb/s > Stream #0.0: Video: rawvideo, bgra, 1024x768, 629145 kb/s, 25 tbr, 1000k > tbn, 25 tbc > [buffer @ 0x1a7db80] w:1024 h:768 pixfmt:bgra > [ffsink @ 0x1a7ddf0] auto-inserting filter 'auto-inserted scaler 0' between > the filter 'src' and the filter 'out' > [scale @ 0x1a7e110] w:1024 h:768 fmt:bgra -> w:1024 h:768 fmt:yuv420p > flags:0xa0000004 > Output #0, mp4, to '/tmp/out.mp4': > Metadata: > encoder : Lavf52.84.0 > Stream #0.0: Video: mpeg4, yuv420p, 1024x768 [PAR 1:1 DAR 4:3], q=2-31, > 200 kb/s, 25 tbn, 25 tbc > Stream mapping: > Stream #0.0 -> #0.0 > Press [q] to stop encoding > frame= 14 fps= 0 q=0.0 size= 702kB time=0.68 bitrate=8454.1kbits/s > dup=frame= 27 fps= 25 q=0.0 size= 1056kB time=1.20 > bitrate=7212.1kbits/s > dup=frame= 40 fps= 25 q=0.0 size= 1411kB time=1.72 > bitrate=6720.9kbits/s > dup= > [snip...] > > > Then it plays it as such: > > mplayer /tmp/out.mp4 > MPlayer SVN-r32624-4.4.4 (C) 2000-2010 MPlayer Team > > Playing /tmp/out.mp4. > libavformat file format detected. > [lavf] stream 0: video (mpeg4), -vid 0 > VIDEO: [MP4V] 1024x768 24bpp 25.000 fps 5798.3 kbps (707.8 kbyte/s) > Clip info: > major_brand: isom > minor_version: 512 > compatible_brands: isomiso2mp41 > encoder: Lavf52.84.0 > ========================================================================== > Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family > Selected video codec: [ffodivx] vfm: ffmpeg (FFmpeg MPEG-4) > ========================================================================== > Audio: no sound > Starting playback... > Movie-Aspect is 1.33:1 - prescaling to correct movie aspect. > VO: [xv] 1024x768 => 1024x768 Planar YV12 > V: 19.1 0/ 0 5% 0% 0.0% 0 0 > > > Exiting... (End of file) > > > Not sure how to define the vcodec to be h264. Is ffodivx the same as h264? > > > > > Now, I hope I'm not getting greedy, but how do I add voice recording to > > > the above stanza? Or do I have to record voice and then package it > > > along with the video in a container as a separate step? > > > > EXAMPLES > > Video and Audio grabbing > > FFmpeg can grab video and audio from devices given that you > specify > > the input format and device. > > > > ffmpeg -f oss -i /dev/dsp -f video4linux2 -i /dev/video0 > > /tmp/out.mpg > > > > Note that you must activate the right video source and channel > > before launching FFmpeg with any TV viewer such as xawtv > > (<http://linux.bytesex.org/xawtv/>) by Gerd Knorr. You also have > to > > set the audio recording levels correctly with a standard mixer. > > > > Audacity is widely used for simple audio editing. > > Great! Thanks Stroller. :) > > -- > Regards, > Mick >
This link was very helpful to me, maybe it can be to you: http://verb3k.wordpress.com/2010/01/26/how-to-do-proper-screencasts-on-linux/
