Codec for Desktop Recording

Hi, I am writing a software like camtasia, where you can
record the desktop screen for video tutorials etc.

I am wondering if ffmpeg is able to support me in that issue.

1.)    Is there a video codec with high compressionrate for pictures which 
don't differ too much?
        (Because desktop pictures predominantly remain the same).
        In fact, is there a video codec specifically designed for 
dektop-screen-capturing?

2.)    Is ffmpeg capable of encoding desktop-pictures in realtime?

Any hints appreciated!

Regards

A.Gallus

Re: Codec for Desktop Recording

On Sun, Nov 30, 2008 at 7:52 PM, Axel Gallus <uh5d <at> rz.uni-karlsruhe.de> wrote:
> Hi, I am writing a software like camtasia, where you can
> record the desktop screen for video tutorials etc.
>
> I am wondering if ffmpeg is able to support me in that issue.
>
> 1.)    Is there a video codec with high compressionrate for pictures which
> don't differ too much?

ZBMV does the job, but it only works on palette-based video (256-color
max).  Note that your choice of formats will depend tremendously on
whether you want a lossy or lossless solution, and what colorspaces
you are willing to encode in.

Most modern video formats only work in the YV12 colorspace, so you
have to be willing to convert from RGB to use them.

Speed-wise, most lossy formats ffmpeg supports are probably fast
enough, especially since you can get away with much faster settings
for screen capture.

Dark Shikari

Re: Codec for Desktop Recording

Axel Gallus wrote:
> Hi, I am writing a software like camtasia, where you can
> record the desktop screen for video tutorials etc.
>
> I am wondering if ffmpeg is able to support me in that issue.
>
> 1.)    Is there a video codec with high compressionrate for pictures which 
> don't differ too much?
>         (Because desktop pictures predominantly remain the same).
>         In fact, is there a video codec specifically designed for 
> dektop-screen-capturing?
>
> 2.)    Is ffmpeg capable of encoding desktop-pictures in realtime?
>
>
> Any hints appreciated!
>
> Regards
>
> A.Gallus
>   

Hi, use flash screen video. Aka flashsv.

MvH
Benjamin Larsson

Re: realmedia rmvb: ready for use?

On date Sunday 2008-11-30 17:25:59 -0500, sean darcy encoded:
> Stefano Sabatini wrote:
> > On date Sunday 2008-11-30 12:12:51 -0500, sean darcy encoded:
> >> Stefano Sabatini wrote:
> >>> On date Sunday 2008-11-30 11:29:06 -0500, sean darcy encoded:
> >>>> Using svn r15958, yesterday.
> >>>>
> >>>> I'm trying to transcode some rmvb - realmedia - files to stream over 
> >>>> mediatomb to a ps3. mencoder ( which uses the actual realmedia codecs ) 
> >>>> chokes because, supposedly, libavformat chokes muxing mp4 if there are 
> >>>> b-frames.
> >>>>
> >>>> I see all the discussion about rv30 and rv40 ( these are the realmedia 
> >>>> codecs, right? ). But I don't see anything on the man page and my 
> >>>> command line doesn't work:
> > [...]
> >>>> I couldn't find any ./configure param. I can see all the rv* files in 
> >>>> libavcodec, but...
> >>> Just be patient and wait, the decoder has been committed but it hasn't
> >>> still activated, this will happen hopefully in these days.
> >>>
> >> Great. Thanks for the response.
> >>
> >> And, I'll be a tester ( especially since I can't find any other way to 
> >> transcode these stupid things ). Is there a way to activate it?
> > 
> > Apply this patch:
> > http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2008-November/056705.html
> > 
> Applied to 15963 ( today's ), but

Achieving constant bit rate H263

Hi folks,

Need help.

I need the following (like) command to produce a near constant bitrate.

ffmpeg -f avi -b 60200 -maxrate 60200 -minrate 60200 -r 9 -g 64 \ 
 -ps 300 -qscale 10 -vcodec h263 -s qcif  -bufsize 602000

However, it comes nowhere near to achieving 60200bit/s unless I manually
apply a qscale setting.  Applying a qscale setting of 31 does indeed
easily meet the target bitrate, granted at very poor quality, so it is
possible.  

However without the qscale ffmpeg seems to make no attempt at all to
honour the max bitrate and throws many buffer overflows instead.
Producing a video varying between 56kbit/s and 135kbit/s.

Is there a parameter similar to qscale that is more dynamic and will use
the 60200 and no more by lowering the quantizer when needed?

Unfortunately I cannot do a 2 pass encoding :(

Thanks :)

Paul

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Re: Achieving constant bit rate H263

On Mon, Dec 1, 2008 at 1:11 AM, Paul Campbell <P.j.Campbell <at> kainos.com> wrote:
> Hi folks,
>
> Need help.
>
> I need the following (like) command to produce a near constant bitrate.
>
> ffmpeg -f avi -b 60200 -maxrate 60200 -minrate 60200 -r 9 -g 64 \
>  -ps 300 -qscale 10 -vcodec h263 -s qcif  -bufsize 602000
>
> However, it comes nowhere near to achieving 60200bit/s unless I manually
> apply a qscale setting.  Applying a qscale setting of 31 does indeed
> easily meet the target bitrate, granted at very poor quality, so it is
> possible.
>
> However without the qscale ffmpeg seems to make no attempt at all to
> honour the max bitrate and throws many buffer overflows instead.
> Producing a video varying between 56kbit/s and 135kbit/s.
>
> Is there a parameter similar to qscale that is more dynamic and will use
> the 60200 and no more by lowering the quantizer when needed?

Yes, it's called -maxrate.

But are you sure you know what -bufsize means?  You're using a
10-second bitrate buffer: are you sure that when measuring the peak
bitrate you're measuring using an equivalent buffer?

Dark Shikari

Re: realmedia rmvb: ready for use?

Stefano Sabatini wrote:
........
> 
> No need to patch it anymore, just checkout r15968 (remember to make
> distclean).
> 

I used svn-r15970. And it worked, I think. The "Unsupported video codec" 
line is a little scary, but doesn't seem to be true. Perhaps a relic?

And it plays, in mplayer at least. I'll try to stream it to the ps3 
tomorrow.

Thanks to you, SOC and everyone else who put all this together.

sean

  ffmpeg -y -i test.rmvb -threads 0 -vcodec libx264 -crf 18 -vpre hq -b 
1372k -bt 500k -bf 16 -acodec libmp3lame -ab 64k -f mp4 test.mp4
FFmpeg version SVN-r15970, Copyright (c) 2000-2008 Fabrice Bellard, et al.
   configuration: --prefix=/usr --enable-libmp3lame --enable-libvorbis 
--enable-libtheora --enable-libfaad --enable-libfaac --enable-libgsm 
--enable-libxvid --enable-libx264 --enable-postproc --enable-shared 
--enable-pthreads --enable-gpl --enable-nonfree --enable-swscale 
--enable-avfilter --enable-avfilter-lavf --cpu=k8 --disable-debug 
--enable-libschroedinger --disable-encoder=libschroedinger 
--enable-libdirac --disable-decoder=libdirac
   libavutil     49.12. 0 / 49.12. 0
   libavcodec    52. 5. 0 / 52. 5. 0
   libavformat   52.23. 1 / 52.23. 1

Re: CODEC_FLAG_TRELLIS_QUANT

2008/11/11 Stefano Sabatini <stefano.sabatini-lala <at> poste.it>

> On date Tuesday 2008-11-11 16:15:27 -0500, Franco Amato encoded:
> > Hi to all,
> > I successfully updated to the svn version my ffmpeg installation.
> > In my old code I set a CODEC_FLAG_TRELLIS_QUANT extraflag for the mp4
> > format.
> > I tried to recompile the code with the new libraries and now I can't.
> > The flag has been removed?
> > Where I can check these changes without be a patch developer
> > but a normal developer?
>
> svn log is your friend.
>
> For example:
> svn log libavcodec/utils.c
>
> r13722 contains the relevant change, the trell flag had been ifdeffed
> and has been automatically dropped when libavcodec bumped major
> version 51 -> 52.

Hi Stefano , so now is not possible to set this flag?
How must I do?

>
> Regards.

Regards ,
Franco

qt-faststart very slow

Hey guys,

We're running an automated transcoder daemon using FFMpeg. We're also  
using qt-faststart to move the MOOV atom to the beginning of our H264  
files. In certain cases this however runs extremely slow.

Just getting into the office I noticed one of them running for about  
12 hours, for a relatively small file.. Are there known bugs with this  
tool (possibly with slightly corrupted files?) Is anyone aware of  
alternative tools that achieve the same thing?

Thanks very much,
Evert

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Re: CODEC_FLAG_TRELLIS_QUANT

On date Monday 2008-12-01 09:44:22 -0500, Franco Amato encoded:
> 2008/11/11 Stefano Sabatini <stefano.sabatini-lala <at> poste.it>
> 
> > On date Tuesday 2008-11-11 16:15:27 -0500, Franco Amato encoded:
> > > Hi to all,
> > > I successfully updated to the svn version my ffmpeg installation.
> > > In my old code I set a CODEC_FLAG_TRELLIS_QUANT extraflag for the mp4
> > > format.
> > > I tried to recompile the code with the new libraries and now I can't.
> > > The flag has been removed?
> > > Where I can check these changes without be a patch developer
> > > but a normal developer?
> >
> > svn log is your friend.
> >
> > For example:
> > svn log libavcodec/utils.c
> >
> > r13722 contains the relevant change, the trell flag had been ifdeffed
> > and has been automatically dropped when libavcodec bumped major
> > version 51 -> 52.
> 
> Hi Stefano , so now is not possible to set this flag?
> How must I do?

Check the -trellis option.

Also relevant (since it is currently not documented):
http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/77138/