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307 lines
9.1 KiB
307 lines
9.1 KiB
<html>
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<head>
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<title> Linux Video Stream Processing Tool - Examples</title>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<meta name="keywords" content="DVD, digital video, DV, encoder, divx,
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DivX;-), lame, source, posix, avifile, opendivx, codec, linux, AC3,
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program stream, video, audio, transcode, decoder, stream, YV12">
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</head>
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<body bgcolor=#CDB5CD>
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<a name=top></a>
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<table cellspacing="10" cellpadding="0" border="0" width="100%">
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<tr>
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<td align=left valign="top" width=30% bgcolor="#a0a0a0">
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<table border="0" cellpadding="10" cellspacing="3" font size=+2 bgcolor="#ffffff" width=100%>
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<td align="left" bgcolor="#e9e9e9"> <FONT
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FACE="Lucida,Helvetica"> <font>Digital Video</font>
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</tr>
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<tr>
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<td>
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This chapter gives an introduction to Digital Video
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processing with transcode. Here is a list of features:
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<ul>
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<li> AVI-files with Digital Video streams can be
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decoded with
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<ul>
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<li><i>libdv</i> (default)
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<li><i>ffmpeg</i> (-x ffmpeg)
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</ul>
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<li> concatenating clips with directory mode and option "-i <i>direname</i>"
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before processing.
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<li> a couple of fast or high-quality de-interlace
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<a href=filter.html#video>filters</a> available to
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enhance the quality.
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<li> support for encoding to DV with <i>libdv</i> as raw
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stream or interleaved AVI-file.
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<li> pass-through mode: raw DV -> AVI-file conversion.
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</ul>
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Unfortunately, while most linux player happily accept the AVI-DV files
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produced by <i>transcode</i>, the nonlinear DV video
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editor <a href=http://www.schirmacher.de/arne/kino/><i>kino</i></a>
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refuses to work with them.
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<ul>
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<li> <a href="dv.html#dv"> <FONT FACE="Lucida,Helvetica">
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Digital Video DV</font></a>
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<ul>
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<li><a href="dv.html#dv_avi"> <FONT FACE="Lucida,Helvetica">
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AVI files</font></a>
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<li><a href="dv.html#dv_dv"> <FONT FACE="Lucida,Helvetica">
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DV streams</font></a>
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</ul>
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<p>
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<li> <a href="#pass"> <FONT FACE="Lucida,Helvetica">
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pass-through mode</font></a> <p>
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<li> <a href="#interlace"> <FONT FACE="Lucida,Helvetica">
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de-interlacing guide</font></a> <p>
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<li> <a href="#alias"> <FONT FACE="Lucida,Helvetica">
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anti-aliasing guide</font></a>
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</td>
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</tr>
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</table>
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</table>
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<a name=dv></a>
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<table cellspacing="10" cellpadding="0" border="0" width="100%">
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<tr>
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<td align=left valign="top" width=30% bgcolor="#a0a0a0">
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<table border="0" cellpadding="10" cellspacing="3" font size=+2 bgcolor="#ffffff" width=100%>
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<td align="left" bgcolor="#e9e9e9">
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<font>Digital Video (DV)
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---> MPEG-4</font>
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</tr>
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<tr>
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<td>
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Here is a 3 step guide to convert a DV tape to a compressed AVI
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MPEG-4 movie clip under linux using <i>transcode</i>. For a
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selection of a video codec implementation supported by
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transcode consult the <a href=modules.html> modules</a> info-page.
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<ul>
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<li> You need Arne Schirmacher's nice tool <i>dvgrab</I>
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to transfer the DV tape to disk. Make sure, you use
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the "--format dv2" option and maybe "--autosplit" to split
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the tape into small pieces. Use AVI files, since
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libdv sound seems to be broken. Optionally, use <br><br>
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<FONT color=red> tcprobe -i file.avi <br><br>
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</i> to find out important parameters: For example:
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<p><code>
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[tcprobe] RIFF data, AVI video
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[avilib] V: 25.000 fps, codec=dvsd, frames=633, width=720, height=576 <br>
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[avilib] A: 48000 Hz, format=0x01, bits=16, channels=2, bitrate=1536
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kbps, <br>
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[avilib] 633 chunks, 4861528 bytes <br>
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[tcprobe] summary for test-2002.10.04_14-47-25.avi, (*) = not default, 0 = not detected<br>
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import frame size: -g 720x576 [720x576] <br>
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frame rate: -f 25.000 [25.000] frc=3 <br>
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audio track: -a 0 [0] -e 48000,16,2 [48000,16,2] -n 0x1 [0x2000] (*)
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bitrate=1536 kbps <br>
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length: 633 frames, frame_time=40 msec <br>
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</code><p>
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Fortunately, the auto-probing feature
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of <i>transcode</i> takes care of these details.
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<br><br>
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<li> To encode the clips, we have a number of options:
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<ul>
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<li> writing a shell script, that feeds transcode with each
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file,
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<li> using <i>avimerge</i> to create a single
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input file,
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<li> using the directory mode with option "-i". This
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works only in connection with the import module <i>import_dv.so</i>.
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</ul>
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<a name=dv_avi><h3>AVI-file</h3></a>
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Here,
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we use a single AVI-file <i>file.avi</i> with "dvsd" codec
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as an example: <p>
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<table>
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<tr>
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<td align=left valign="top" bgcolor="#ccffcc">
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transcode</td>
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<td align=left valign="top" bgcolor="#ccffcc">
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-i file.avi -x dv,avi</td>
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</tr>
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<tr><td></td>
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<td align=left valign="top" bgcolor="#ccffcc">
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-I 1 -C 1 -z -k </td>
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</tr>
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<td></td><td align=left valign="top" bgcolor="#ccffcc">
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-o file-divxmp3.avi -y divx4</td></tr>
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</table>
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<br>
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We use <i>import_avi.so</i> to extract the audio,
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which works flawless. Note that the audio is found in two
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places in the AVI-file. Firstly, interleaved in the DV video
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frame and secondly, the PCM audio track itself.
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This makes it possible to use the import module "dv" for audio
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extraction as long <i>libdv</i> is broken.<br>
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Note: some non-dvgrab produced AVI-files may have the audio
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ripped from the DV frames. In this case, you must use "-x
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dv,avi" or "-x dv,X", were X is one of (raw,mp3,ac3).
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<br>
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You can also reduce
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the picture to a quarter size "-r 2" to get rid of
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the interlace artifacts and don't need the de-interlace
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option "-I 1". This option is the fastes de-interlacing
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available, but is a simple interpolation.
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You might also want to try
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out the anti-aliasing feature with "-C 1" to process the
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whole frame but this is slow.
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The option "-z -k" flips the frame and make the
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necessary color space changes for the encoder.
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<a name=dv_dv><h3>DV stream</h3></a>
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Put all AVI-files or raw DV stream into a subdirectory,
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e.g., named "tape/". <p>
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<table>
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<tr>
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<td align=left valign="top" bgcolor="#ccffcc">
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transcode</td>
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<td align=left valign="top" bgcolor="#ccffcc">
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-i tape/ </td>
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</tr>
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<tr><td></td>
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<td align=left valign="top" bgcolor="#ccffcc">
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-I 3 -C 2 -z -k </td>
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</tr>
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<td></td><td align=left valign="top" bgcolor="#ccffcc">
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-o tape-divxmp3.avi -y divx4</td></tr>
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</table>
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<br>
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The necessary import module is autodetected. <i>tccat</i> extracts
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the video stream of all AVI-files and concatenates them together to
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make the clips appear as a single DV stream for <i>transcode</i>.
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Here, the de-interlace option "-I 3",
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which drops one half-frame and interpolates by zooming to full
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frame size and, in principle, removes the interlace artifacts. We also try
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the anti-aliasing feature with "-C 2" to process the
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full frame afterwards, but this is slow.
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<p>
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<li> Well, that's it. Use <i>avimerge</i> to glue the
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matching clips together and burn the resulting file
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to CD.
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</ul>
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</TV>
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</table>
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</table>
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<a name=pass></a>
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<table cellspacing="10" cellpadding="0" border="0" width="100%">
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<tr>
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<td align=left valign="top" width=30% bgcolor="#a0a0a0">
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<table border="0" cellpadding="10" cellspacing="3" font size=+2 bgcolor="#ffffff" width=100%>
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<td align="left" bgcolor="#e9e9e9">
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<font>pass-through mode</font>
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</tr>
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<tr>
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<td>
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The pass-through mode is able to wrap raw Digital Video
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streams into AVI-files with the following command. Note, that
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the interleaved raw audio data can be transcoded to a separate
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audio track with the codec of your choice. However, this
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does not save space since Digital Video has identical frame
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size independent of the presence of audio.
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<p>
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<code>
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transcode -i raw.dv -P 1 -o raw.avi -y raw
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</code>
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<p>
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The opposite way is achieved by:
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<p>
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<code>
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tcextract -i raw.avi -x raw > raw.dv
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</code>
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<p>
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</table>
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</table>
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<a name=interlace></a>
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<table cellspacing="10" cellpadding="0" border="0" width="100%">
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<tr>
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<td align=left valign="top" width=30% bgcolor="#a0a0a0">
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<table border="0" cellpadding="10" cellspacing="3" font size=+2 bgcolor="#ffffff" width=100%>
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<td align="left" bgcolor="#e9e9e9">
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<font>de-interlacing guide</font>
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</tr>
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<tr>
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<td>
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Underway.
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Tilmann Bitterberg did some testing of de-interlace filters available in
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transcode. You can view and read the result
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<a href=http://tibit.org/video/> here</a>.
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</table>
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</table>
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<a name=alias></a>
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<table cellspacing="10" cellpadding="0" border="0" width="100%">
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<tr>
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<td align=left valign="top" width=30% bgcolor="#a0a0a0">
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<table border="0" cellpadding="10" cellspacing="3" font size=+2 bgcolor="#ffffff" width=100%>
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<td align="left" bgcolor="#e9e9e9">
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<font>anti-aliasing guide</font>
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</tr>
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<tr>
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<td>
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Underway.
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</table>
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</table>
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<!-- hhmts start -->
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Last modified: Fri Dec 6 16:25:56 Europe/Berlin 2002
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<!-- hhmts end -->
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</body> </html>
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