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246 lines
8.1 KiB
246 lines
8.1 KiB
4 years ago
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Import_nvrec Documentation
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* Index
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-------
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- Overview
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- Schematics
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- Usage
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- Requierements
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- Examples
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- Tips
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- Changes
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* Overview
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----------
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This import module connects NVrec - a very good v4l1/v4l2 grabber -
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and transcode. NVrec is very good, because of its audio/video synch
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mechanism which maintains perfect A/V synch over a really long time.
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Read more about NVrec at http://www.ee.up.ac.za/~justin/
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"Isn't this braindead? I though NVrec can write divx/divx4/... files
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as well?" You might ask. Yes, this is true, but transcode has much
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more features, such as better deinterlacing, video postprocessing,
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clipping, etc.
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In order to accomplish the connection between NVrec and transcode I
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wrote an "export module" for NVrec called RAWrec (which is now
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divx4rec -o raw://) In this mode, divx4rec basically writes its
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video data to stdout (where it gets capured from transcode) and the
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audio data to a mp3 file in an AVI container.
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Before you get completly confused, here are some usage examples
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$ transcode -V -i /dev/v4l2/capture0 -x nvrec,null -y xvidcvs,null \
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-o video.avi -g 512x384 -u 100 -m audio.avi -H0
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Since import_nvrec only works in YUV mode '-V' is mandatory.
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Use your v4l1/2 device as the input file or transcode will assume
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/dev/video.
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Write encoded video stream to video.avi.
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Write audio stream to audio.avi.
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Framesize is 512x384.
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Use 100 buffers.
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You now have two AVI files: The video only in video.avi and the
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audio only in audio.avi. Use avimerge to multiplex them.
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$ avimerge -i video.avi -p audio.avi -a 0 -o complete.avi
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Easy, eh?
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* Schematics
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------------
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/---\
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\---/
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\|/
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/--------\ /-----------\
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| | <----- recording parameters <--- | |
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|divx4rec| | transcode |
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|-o raw: | -----> video stream -----------> | |
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\--------/ \-----------/
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\|/ \|/
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/---------\ /---------\
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|audio.avi| |video.avi|
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\---------/ \---------/
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\______________________________________________/
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avimerge
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\|/
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/------------\
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|complete.avi|
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\------------/
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* Usage
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----------------
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divx4rec gets its options from transcode meaning transcode's defaults
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apply.
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Audio parameters can be specified through transcodes '-e' option,
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the mp3 bitrate is controlled with '-b' , eg
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$ transcode (..) -e 44100,16,2 -b 192
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Everything should work like you expect it to work.
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If you don't specify the '-m' option, audio will be written to
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audio.avi. If you need to pass special options to divx4rec, you can
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pass options by supplying a string after the module name, just write
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down the divx4rec options. This can be useful if you want to control
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NVrecs buffer usage
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$ transcode (..) -x nvrec="-H 90 -L 10 -M 50"
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The divx4rec command to be executed will get printed out, look for
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something like
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[import_nvrec.so] divx4rec -o raw://audio.avi -w 512 -h 384 -s -b 16 -r 48000 -ab 128 -aq 5
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* Requierements
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---------------
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RAWrec is now integrated into NVrec. Since it was heavily based on divx4rec
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anyway it became a special output mode of divx4rec. NVrec lives at
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http://nvrec.sf.net
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If you only want divx4rec out of NVrec, configure with
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$ ./configure --without-avifile --without-rte \
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--without-ffmpeg --without-quicktime --without-sdl --without-mad
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and copy divx4rec to some place in your $PATH.
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$ install -m 755 divx4rec /usr/local/bin
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Done
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* Examples
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----------
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Record video at 512x384 to XviD, audio to mp3 at bitrate 128
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$ transcode -V -i /dev/video -x nvrec,null -y xvidcvs,null \
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-g 512x384 -u 100 -o video.avi -H0
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Record video at 512x384 to XviD, audio to mp3 at bitrate 192 with
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parameters 44100,16,2
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$ transcode -V -i /dev/video -x nvrec,null -y xvidcvs,null \
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-g 512x384 -u 100 -o video.avi -b 192 -e44100,16,2 -H0
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Write audio stream to audio-only.avi
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$ transcode -V -i /dev/video -x nvrec,null -y xvidcvs,null \
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-g 512x384 -u 100 -o video.avi -m audio-only.avi -H0
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Get audio from /dev/sound/dsp and video from /dev/v4l2/capture0
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$ transcode -V -i /dev/v4l/capture0 -p /dev/sound/dsp \
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-x nvrec,null -y xvidcvs,null \
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-g 512x384 -u 100 -o video.avi -m audio-only.avi -H0
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Multiplex the files
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$ avimerge -i video.avi -p audio.avi -a 0 -o complete.avi
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* Tips
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-------
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To squeeze out even more fps you can tell divx4rec to not encode the audio
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to mp3 and write a WAV file instead. Sebastian <scut@nb.in-berlin.de>
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writes in http://www.theorie.physik.uni-goettingen.de/
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pipermail/transcode-users/2002-June/002575.html (in one line)
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(adjusted by tibit to reflect the new syntax)
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"I use this command line to record from TV (after setting the correct channel
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with xawtv):
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transcode --duration 01:00:00 \
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-x nvrec="-wav",null
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-i /dev/video0 -V -H0 -u 100 \
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-g 576x432 \
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-y divx5,null -w 1200 -o output-video.avi \
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-e 44100,16,2 \
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-J dilyuvmmx
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This produces the files "output-video.avi" and "audio.avi", which is just a
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WAV file. By using this method instead of encoding directly to MP3, I can
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archieve a +3 or +4 frame rate and can encoder a higher solution. After
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recording, I merge both files:
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transcode -i output-video.avi -p audio.wav -P 1 -b 128,0 \
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-o output-complete.avi -y raw
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The output-complete.avi file is the finished recording, but with ads. I use
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'avidemux' to cut out the commercials, which is easy since avidemux has a
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"skip to next keyframe" button. Usually at the end of commercials there is a
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new keyframe. Use the markers begin/end and the delete option from the
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"mark" menu to cut the ads out. Then write a new file with A/V to disk. For
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me the smart mode sometimes segfaults, and I do not use it."
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---------
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Another Usage scenario is described by Christoph Gaitzsch
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<christoph.gaitzsch@t-online.de> in
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http://www.theorie.physik.uni-goettingen.de/pipermail/transcode-users/2002-August/003946.html
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(adjusted by tibit to reflect the new syntax)
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"I also use my PC as a video recorder on a Athlon 1G. After
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experimenting much with transcode, nvrec, lavrec, etc. I now capture
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with transcode via nvrec, save this as yuv4mpeg raw stream to a fast
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disk and postprocess later. I found that the quality is much better
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when encoding in a separate step than live, even when I have no
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framedrops.
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Basically I record with the following commands:
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Pass 1 (recording)
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transcode -V -i /dev/video0 -x nvrec="-N 32",null -y yuv4mpeg,null
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-o out_video.yuv4mpeg -g 384x288 -u 100 -m out_audio.avi
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-H0 -f 25
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Pass 2 (encoding)
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nice -19 transcode -i out_video.yuv4mpeg -p out_audio.avi
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-g 384x288 -f 25 -x yuv4mpeg,mp3 -y ffmpeg4 -w 3000
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-o out.avi -u 100 -J dnr,yuvdenoise,32detect=force_mode=3
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The advantage is, that the recording stage needs ~5% CPU time, so I
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have no framedrops even when the machine runs updatedb or other,
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CPU-consuming cron jobs. It is also possible to record while encoding
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(because it's niced). Since I schedule my recordings via at and the
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second pass lasts very long (~4fps), it's an issue to record at low
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CPU usage.
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The filters used in this way, dnr first, then yuvdenoise give me very
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good picture quality. Thanks to Jason Lunz' for his work on filter
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comparison."
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* Changes
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---------
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(newest last)
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- NVrec interface changed based on discussion with Justin. RAWrec is now
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divx4rec -o raw:// in raw file mode.
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- Use -i ... as input video device.
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- Use -H0 to disable conflicting autoprobing with import_v4l
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- Added Sebastians tip for encoding to wav
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- Justin renamed DIVX4rec to divx4rec
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- Syntax changed. Do not use transcode's -F anymore, if you need to pass special
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options to nvrec use
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-x nvrec="-S2 -N32",null
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Have fun
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08/2002 Tilmann Bitterberg <transcode@tibit.org>
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