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513 lines
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513 lines
15 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>Miscellaneous</font>
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</tr>
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<tr>
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<td>
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<ul>
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<li> <a href="#para"> <FONT FACE="Lucida,Helvetica">
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Overview on the
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resizing/clipping options</font></a> <br>
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</uL>
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<ul>
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<li> <a href="#maudio"> <FONT FACE="Lucida,Helvetica">
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AVI-files with multiple audio tracks</font></a><br>
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</ul>
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<ul>
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<li> <a href="#pass"> <FONT FACE="Lucida,Helvetica">
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pass-through modes </font></a>
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<ul>
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<li><a href="#pass_1"> <FONT FACE="Lucida,Helvetica">
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replacing audio</font></a>
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<li><a href="#pass_2"> <FONT FACE="Lucida,Helvetica">
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creating music clips</font></a>
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<li><a href="#pass_3"> <FONT FACE="Lucida,Helvetica">
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audio recompression</font></a>
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<li><a href="#pass_4"> <FONT FACE="Lucida,Helvetica">
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fixing truncated AVI files</font></a>
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</ul>
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<br>
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<li> <a href="#audio"> <FONT FACE="Lucida,Helvetica">
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audio only conversion</font></a>
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<br>
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<ul>
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<li><a href="#aud_1"> <FONT FACE="Lucida,Helvetica">
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audio track -> MP3</font></a>
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<li><a href="#aud_2"> <FONT FACE="Lucida,Helvetica">
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audio track -> PCM</font></a>
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<li><a href="#aud_3"> <FONT FACE="Lucida,Helvetica">
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ASF audio -> MP3</font></a>
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</ul>
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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=para></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>
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resizing/clipping options
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</font>
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</tr>
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<tr>
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<td>
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<br> by Steffen Klupsch <steffen@vlsi.informatik.tu-darmstadt.de>
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<P>
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Boundary Conditions (valid for transcode-0.5.0 and later):
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<UL>
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<LI> maximum image size is 1024x768
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<LI> The video frame operations ordering is fixed:
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"-j -I -X -B -Z -Y -r -z -l -k -K -G -C"
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(executed from left to right)
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<LI> Shrinking the image with '-B' is not possible
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if the image width/height is not a multiple of 32.
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<LI> Expanding the image with '-X' is not possible
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if the image width/height is not a multiple of 32.
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<LI> The final frame width/height should be a multiple of 8.
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(to avoid encoding problems with some divx codecs)
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<OL>
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<LI> Reducing the video height/width by 2,4,8
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Option '-r factor' can be used to shrink the video image by a
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constant factor, this factor can be 2,4 or 8.
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<LI> Clipping and changing the aspect ratio
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transcode uses 3 steps to produce the input image for the
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export modules
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<OL>
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<LI> Clipping of the input image.
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<LI> Changing the aspect ratio of the 1) output.
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<LI> Clipping of the 2) output.
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</OL>
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</OL>
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</UL>
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<P>
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Used Options:
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<OL>
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<LI> The first clipping is defined by the option <br>
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'-j top[,left[,bottom[,right]]]' <br>
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if you don't specify all parameters, they will be assumed to be
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symmetric to the others.
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<P>
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-j 80 is expanded to -j 80,0,80,0 (top,left,bottom,right)<br>
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-j 80,8 is expanded to -j 80,8,80,8<br>
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-j 80,8,10 is expanded to -j 80,8,10,8<br><br>
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<LI> Changing the aspect ration can be done in 3 ways:
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<UL>
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<LI> (fast) shrinking the image with option '-B n[,m]'
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<LI> (fast) expanding the image with option '-X n,[m]'
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<LI> (high quality) resizing with option '-Z wxh'
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</UL><br>
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<LI> The 2nd clipping is defined by the option
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<br>
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'-Y top[,left[,bottom[,right]]]'<br>
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if you don't specify all parameters, they will be assumed to be
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symmetric to the others.
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</OL>
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<P>
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Examples on Usage:
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<OL>
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<LI> Input data '16:9' 'widescreen' DVD data,
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output data should have 4:3 aspect ratio without black border.
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<br>
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Analyze the input data, we assume a black border at the top and
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bottom of 66 pixel in a 720x576 pixel frame.
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<p>
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<OL>
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<LI> Using the fast resizing option -B,
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shrinking the height to reach a correct aspect ratio:
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'-j 32,0 -B 4,0 -Y 24,0'
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Final image size: 720x336 Pixel
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<LI> Using the fast resizing options -X and -B,
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removing 1% at the left&right border, expanding the image width
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to PAL resolution, and shrinking the height to reach a
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correct aspect ratio:<br>
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'-j 32,8 -X 0,2 -B 3,0 -Y 24,0'<br>
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Final image size: 768x368 Pixel
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<LI> Using the fast -X resizing, expanding the image width,
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but removing 3% of the image at the left and the right border:<br>
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'-j 64,24 -X 0,7'<br>
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Final image size: 896x448 Pixel
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<LI> Using the slower -Z resizing, expanding the image width to PAL
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resolution:<br>
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'-j 68,0 -Z 768x360'<br>
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Final image size: 768x360 Pixel
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<LI> Using the slower -Z resizing, 800 Pixel image width:<br>
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'-j 66,0 -Z 800x368'<br>
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Final image size: 800x368 Pixel
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<LI> Using the slower -Z resizing, expanding the image width:<br>
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'-j 64,0 -Z 960x448'<br>
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Final image size: 960x448 Pixel
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</OL>
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<p>
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<LI> Input data '16:9' DVD data without black borders,
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output data should have 4:3 aspect ratio.
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<p>
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<OL>
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<LI> Using the fast resizing option -B, <br>
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shrinking the height to reach correct aspect ratio:
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'-B 4,0'<br>
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Final image size: 720x448 Pixel
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<LI> Using the fast -X resizing, expanding the image width,
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but removing 3% of the image at the left and the right border:<br>
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'-j 0,24 -X 0,7'<br>
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Final image size: 896x576 Pixel
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<LI> Using the slower -Z resizing, expanding the image width
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to PAL resolution:<br>
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'-Z 768x472'<br>
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Final image size: 768x472 Pixel
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<LI> Using the slower -Z resizing, 800 Pixel image width:<br>
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'-Z 800x480'<br>
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Final image size: 800x480 Pixel
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<LI> Using the slower -Z resizing, expanding the image width:<br>
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'-Z 960x576'<br>
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Final image size: 960x576 Pixel
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</OL>
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</OL>
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<P>
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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 modes</font>
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</tr>
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<tr>
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<td>
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This section is devoted to the pass-through modes
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available, which maybe useful for some, not so common
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situations as outlined below.
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<a name=pass_1><h3>replacing audio</h3></a>
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<a name=pass_2><h3>creating video clips</h3></a>
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Suppose you have mastered a couple of DV clips,
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concatenated to a well defined playtime "clip1.avi" that
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accidently
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correspond to the length of your favorite music clip "clip2.mp3"
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in MP3 format. We want to keep the quality of the video
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and simply replace the PCM audio track. This is done by
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the following command:
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<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 clip.avi -p clip.mp3</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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-P 1 </td>
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</tr>
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<td></td><td align=left valign="top" bgcolor="#ccffcc">
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-o new_clip.avi -y raw</td></tr>
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</table>
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<br>
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Note: The MP3 stream must be identified by <i>tcprobe</i>.
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If this fails, we need to supply the import module options
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"-x dv,mp3" to make sure, the audio is decoded properly.
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The "-y raw" export module simply writes the video chunks
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as is together with the re-encoded audio. MP3 pass-through,
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similar
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to AC3 pass-through with options "-A -N 0x2000" is not yet available.
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<a name=pass_3><h3>audio recompression</h3></a>
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The following situation is not uncommon. Suppose your single
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AVI-file "movie128.avi" is about 2x700MB+15MB, i.e., too large to fit
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on 2 CD's. Fortunately, the audio is MP3 with a bitrate of
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128kbps, which is the default.
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We recompress the audio to 96kbps to reduce the filesize
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below 2x700MB. Let's also double the volume of the sound,
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if possible, or use the recommended value given by <i>tcscan</i>.
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<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 movie128.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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-P 1 -b 96 -s 2.0</td>
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</tr>
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<td></td><td align=left valign="top" bgcolor="#ccffcc">
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-o movie96.avi -y raw</td></tr>
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</table>
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<br>
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This is reasonable fast since video is only passed through
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and the audio quality is still ok.
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After you are done, use avisplit to split the file
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into 2 chunks.
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<a name=pass_4><h3>fixing truncated AVI files</h3></a>
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The AVI file header is updated (written to disk), whenever video/audio
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parameter are set. If transcode or hardware crashes, the truncated file
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is in most cases playable for advanced players.
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Repairing the AVI-file index is also possible via pass-through option "-P3".
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<p>
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<table>
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<tr>
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<td align=left valign=center bgcolor="#ccffcc">
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transcode -i crashed.avi -o new.avi -P3 -u X</td>
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</td>
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</table>
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<br>Option "-u X" with X>>10 enhances pass-through speed.
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</table>
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</table>
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<a name=audio></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>audio only conversion</font>
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</tr>
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<tr>
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<td>
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Audio only conversion is also possible with
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<i>transcode</i>.
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Certainly, there are tons of tools out there, doing the
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same job, so I will concentrate on useful examples, mainly
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DVD ripping and encoding on the fly, using options "-p"
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for input and "-m" for output.
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<a name=aud_1><h3>audio track -> MP3</h3></a>
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Some DVDs have a separate AC3 (Dobly Digital) film soundtrack, which
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you might want to convert to MP3. Music DVDs have
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tracks with uncompressed audio
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which is LPCM format (linear PCM), you want to archive. In this
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particular case, you might need to add "-d" for audio byte swapping.
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You need to check with tcprobe which audio track is the
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right one.
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We do it in 1 step for
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track 2 and write to the file "track.mp3":
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<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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-p /dev/dvd/ -T 1,-1 -a 2 </td>
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</tr>
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<td></td><td align=left valign="top" bgcolor="#ccffcc">
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-y raw -m track.mp3 </td></tr>
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</table>
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<p>
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<a name=aud_2><h3>audio track -> PCM</h3></a>
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If you prefer uncompressed PCM data for further processing, add
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"-N 0x1" in the command above:
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<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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-p /dev/dvd/ -T 1,-1 -a 2</td>
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</tr>
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<td></td><td align=left valign="top" bgcolor="#ccffcc">
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-y raw -m track.pcm -N 0x1</td></tr>
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</table>
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<p>
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<a name=aud_3><h3>ASF audio -> MP3</h3></a>
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I had this ASF (advanced stream format) Genesis audio file
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lying around and tried the <i>avifile</i> import module. Since
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no auto-probing is available for ASF streams in the current
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version, you must play around with the sample rate. CD quality
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is 44100 Hz samplerate:
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<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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-p carpet_crawler_1999.asf -x null,af6</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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-e 44100 -E 44100 -b 112</td>
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</tr>
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<td></td><td align=left valign="top" bgcolor="#ccffcc">
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-y null,raw -m carpet_crawler_1999.mp3</td></tr>
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</table>
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<p>
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</table>
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</table>
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<a name=maudio></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>AVI-files with multiple audio tracks</font>
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</tr>
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<tr>
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<td>
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<a name=xvcd><h3>HowTo:</h3></a>
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Before you start, try to find the best bitrate for video
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encoding
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with multiple audio tracks by using <i>tcprobe</i> with
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option "-b n*128", for example, if you want n MP3 audio
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tracks with 128kbps bitrate each.<br>
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A first session produces the file movie.avi with a single audio
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track "-a 0". Now, we use a similar command to extract a second
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audio
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track from the source. Suppose, we used the example modules
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"vmod,amod"
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for video and audio extraction.<p>
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The second session goes as follows. This session will be much
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faster, since no video is de/encoded.<p>
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<Ul>
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<li>
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(1) transcode the second audio track "-a 1" into an AVI
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container file named add-on.avi This looks like:
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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 -i (...) -x null,amod -g 0x0 -y raw -a 1
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-o add-on.avi -u 50 </tr>
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</table>
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<p>
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The resulting file is only a temporary file but enables
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proper processing with <i>avimerge</i>. The export
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module "-y raw" is fine, since it writes proper (0 bytes)
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video frames.
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Set video import module to "null". If all goes well,
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both files should be identical with respect to the number
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of frames. Choose the proper audio track with "-a". Try also to
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increase the internal buffers "-u" for speedup.<p>
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<li>(2) merge this track into movie.avi
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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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avimerge -i movie.avi -o dualaudiomovie.avi -p add-on.avi
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</tr>
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</table>
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<p>
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<li> (3) Repeat steps (1-2) for even more audio tracks, if you
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wish.
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For best results, I recommend doing this procedure with a single
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AVI movie file. All <i>avi*</i> post-processing tools now support
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multiple audio tracks.<p>
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--- <br>
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Note: <i>transcode</i> supports reading from multiple-audio tracks
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but only writes (exports) to single audio/video AVI-files.
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</table>
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</table>
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<!-- hhmts start -->
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Last modified: Thu May 16 12:59:16 CEST 2002
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<!-- hhmts end -->
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</body> </html>
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