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<html>
<head>
<title> Linux Video Stream Processing Tool - Examples</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="DVD, digital video, DV, encoder, divx,
DivX;-), lame, source, posix, avifile, opendivx, codec, linux, AC3,
program stream, video, audio, transcode, decoder, stream, YV12">
</head>
<body bgcolor=#CDB5CD>
<a name=top></a>
<table cellspacing="10" cellpadding="0" border="0" width="100%">
<tr>
<td align=left valign="top" width=30% bgcolor="#a0a0a0">
<table border="0" cellpadding="10" cellspacing="3" font size=+2 bgcolor="#ffffff" width=100%>
<td align="left" bgcolor="#e9e9e9"> <FONT
FACE="Lucida,Helvetica"> <font>Miscellaneous</font>
</tr>
<tr>
<td>
<ul>
<li> <a href="#para"> <FONT FACE="Lucida,Helvetica">
Overview on the
resizing/clipping options</font></a> <br>
</uL>
<ul>
<li> <a href="#maudio"> <FONT FACE="Lucida,Helvetica">
AVI-files with multiple audio tracks</font></a><br>
</ul>
<ul>
<li> <a href="#pass"> <FONT FACE="Lucida,Helvetica">
pass-through modes </font></a>
<ul>
<li><a href="#pass_1"> <FONT FACE="Lucida,Helvetica">
replacing audio</font></a>
<li><a href="#pass_2"> <FONT FACE="Lucida,Helvetica">
creating music clips</font></a>
<li><a href="#pass_3"> <FONT FACE="Lucida,Helvetica">
audio recompression</font></a>
<li><a href="#pass_4"> <FONT FACE="Lucida,Helvetica">
fixing truncated AVI files</font></a>
</ul>
<br>
<li> <a href="#audio"> <FONT FACE="Lucida,Helvetica">
audio only conversion</font></a>
<br>
<ul>
<li><a href="#aud_1"> <FONT FACE="Lucida,Helvetica">
audio track -> MP3</font></a>
<li><a href="#aud_2"> <FONT FACE="Lucida,Helvetica">
audio track -> PCM</font></a>
<li><a href="#aud_3"> <FONT FACE="Lucida,Helvetica">
ASF audio -> MP3</font></a>
</ul>
</td>
</tr>
</table>
</table>
<a name=para></a>
<table cellspacing="10" cellpadding="0" border="0" width="100%">
<tr>
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<table border="0" cellpadding="10" cellspacing="3" font size=+2 bgcolor="#ffffff" width=100%>
<td align="left" bgcolor="#e9e9e9">
<font>
resizing/clipping options
</font>
</tr>
<tr>
<td>
<br> by Steffen Klupsch <steffen@vlsi.informatik.tu-darmstadt.de>
<P>
Boundary Conditions (valid for transcode-0.5.0 and later):
<UL>
<LI> maximum image size is 1024x768
<LI> The video frame operations ordering is fixed:
"-j -I -X -B -Z -Y -r -z -l -k -K -G -C"
(executed from left to right)
<LI> Shrinking the image with '-B' is not possible
if the image width/height is not a multiple of 32.
<LI> Expanding the image with '-X' is not possible
if the image width/height is not a multiple of 32.
<LI> The final frame width/height should be a multiple of 8.
(to avoid encoding problems with some divx codecs)
<OL>
<LI> Reducing the video height/width by 2,4,8
Option '-r factor' can be used to shrink the video image by a
constant factor, this factor can be 2,4 or 8.
<LI> Clipping and changing the aspect ratio
transcode uses 3 steps to produce the input image for the
export modules
<OL>
<LI> Clipping of the input image.
<LI> Changing the aspect ratio of the 1) output.
<LI> Clipping of the 2) output.
</OL>
</OL>
</UL>
<P>
Used Options:
<OL>
<LI> The first clipping is defined by the option <br>
'-j top[,left[,bottom[,right]]]' <br>
if you don't specify all parameters, they will be assumed to be
symmetric to the others.
<P>
-j 80 is expanded to -j 80,0,80,0 (top,left,bottom,right)<br>
-j 80,8 is expanded to -j 80,8,80,8<br>
-j 80,8,10 is expanded to -j 80,8,10,8<br><br>
<LI> Changing the aspect ration can be done in 3 ways:
<UL>
<LI> (fast) shrinking the image with option '-B n[,m]'
<LI> (fast) expanding the image with option '-X n,[m]'
<LI> (high quality) resizing with option '-Z wxh'
</UL><br>
<LI> The 2nd clipping is defined by the option
<br>
'-Y top[,left[,bottom[,right]]]'<br>
if you don't specify all parameters, they will be assumed to be
symmetric to the others.
</OL>
<P>
Examples on Usage:
<OL>
<LI> Input data '16:9' 'widescreen' DVD data,
output data should have 4:3 aspect ratio without black border.
<br>
Analyze the input data, we assume a black border at the top and
bottom of 66 pixel in a 720x576 pixel frame.
<p>
<OL>
<LI> Using the fast resizing option -B,
shrinking the height to reach a correct aspect ratio:
'-j 32,0 -B 4,0 -Y 24,0'
Final image size: 720x336 Pixel
<LI> Using the fast resizing options -X and -B,
removing 1% at the left&right border, expanding the image width
to PAL resolution, and shrinking the height to reach a
correct aspect ratio:<br>
'-j 32,8 -X 0,2 -B 3,0 -Y 24,0'<br>
Final image size: 768x368 Pixel
<LI> Using the fast -X resizing, expanding the image width,
but removing 3% of the image at the left and the right border:<br>
'-j 64,24 -X 0,7'<br>
Final image size: 896x448 Pixel
<LI> Using the slower -Z resizing, expanding the image width to PAL
resolution:<br>
'-j 68,0 -Z 768x360'<br>
Final image size: 768x360 Pixel
<LI> Using the slower -Z resizing, 800 Pixel image width:<br>
'-j 66,0 -Z 800x368'<br>
Final image size: 800x368 Pixel
<LI> Using the slower -Z resizing, expanding the image width:<br>
'-j 64,0 -Z 960x448'<br>
Final image size: 960x448 Pixel
</OL>
<p>
<LI> Input data '16:9' DVD data without black borders,
output data should have 4:3 aspect ratio.
<p>
<OL>
<LI> Using the fast resizing option -B, <br>
shrinking the height to reach correct aspect ratio:
'-B 4,0'<br>
Final image size: 720x448 Pixel
<LI> Using the fast -X resizing, expanding the image width,
but removing 3% of the image at the left and the right border:<br>
'-j 0,24 -X 0,7'<br>
Final image size: 896x576 Pixel
<LI> Using the slower -Z resizing, expanding the image width
to PAL resolution:<br>
'-Z 768x472'<br>
Final image size: 768x472 Pixel
<LI> Using the slower -Z resizing, 800 Pixel image width:<br>
'-Z 800x480'<br>
Final image size: 800x480 Pixel
<LI> Using the slower -Z resizing, expanding the image width:<br>
'-Z 960x576'<br>
Final image size: 960x576 Pixel
</OL>
</OL>
<P>
</table>
</table>
<a name=pass></a>
<table cellspacing="10" cellpadding="0" border="0" width="100%">
<tr>
<td align=left valign="top" width=30% bgcolor="#a0a0a0">
<table border="0" cellpadding="10" cellspacing="3" font size=+2 bgcolor="#ffffff" width=100%>
<td align="left" bgcolor="#e9e9e9">
<font>pass-through modes</font>
</tr>
<tr>
<td>
This section is devoted to the pass-through modes
available, which maybe useful for some, not so common
situations as outlined below.
<a name=pass_1><h3>replacing audio</h3></a>
<a name=pass_2><h3>creating video clips</h3></a>
Suppose you have mastered a couple of DV clips,
concatenated to a well defined playtime "clip1.avi" that
accidently
correspond to the length of your favorite music clip "clip2.mp3"
in MP3 format. We want to keep the quality of the video
and simply replace the PCM audio track. This is done by
the following command:
<p>
<table>
<tr>
<td align=left valign="top" bgcolor="#ccffcc">
transcode</td>
<td align=left valign="top" bgcolor="#ccffcc">
-i clip.avi -p clip.mp3</td>
</tr>
<tr><td></td>
<td align=left valign="top" bgcolor="#ccffcc">
-P 1 </td>
</tr>
<td></td><td align=left valign="top" bgcolor="#ccffcc">
-o new_clip.avi -y raw</td></tr>
</table>
<br>
Note: The MP3 stream must be identified by <i>tcprobe</i>.
If this fails, we need to supply the import module options
"-x dv,mp3" to make sure, the audio is decoded properly.
The "-y raw" export module simply writes the video chunks
as is together with the re-encoded audio. MP3 pass-through,
similar
to AC3 pass-through with options "-A -N 0x2000" is not yet available.
<a name=pass_3><h3>audio recompression</h3></a>
The following situation is not uncommon. Suppose your single
AVI-file "movie128.avi" is about 2x700MB+15MB, i.e., too large to fit
on 2 CD's. Fortunately, the audio is MP3 with a bitrate of
128kbps, which is the default.
We recompress the audio to 96kbps to reduce the filesize
below 2x700MB. Let's also double the volume of the sound,
if possible, or use the recommended value given by <i>tcscan</i>.
<p>
<table>
<tr>
<td align=left valign="top" bgcolor="#ccffcc">
transcode</td>
<td align=left valign="top" bgcolor="#ccffcc">
-i movie128.avi</td>
</tr>
<tr><td></td>
<td align=left valign="top" bgcolor="#ccffcc">
-P 1 -b 96 -s 2.0</td>
</tr>
<td></td><td align=left valign="top" bgcolor="#ccffcc">
-o movie96.avi -y raw</td></tr>
</table>
<br>
This is reasonable fast since video is only passed through
and the audio quality is still ok.
After you are done, use avisplit to split the file
into 2 chunks.
<a name=pass_4><h3>fixing truncated AVI files</h3></a>
The AVI file header is updated (written to disk), whenever video/audio
parameter are set. If transcode or hardware crashes, the truncated file
is in most cases playable for advanced players.
Repairing the AVI-file index is also possible via pass-through option "-P3".
<p>
<table>
<tr>
<td align=left valign=center bgcolor="#ccffcc">
transcode -i crashed.avi -o new.avi -P3 -u X</td>
</td>
</table>
<br>Option "-u X" with X>>10 enhances pass-through speed.
</table>
</table>
<a name=audio></a>
<table cellspacing="10" cellpadding="0" border="0" width="100%">
<tr>
<td align=left valign="top" width=30% bgcolor="#a0a0a0">
<table border="0" cellpadding="10" cellspacing="3" font size=+2 bgcolor="#ffffff" width=100%>
<td align="left" bgcolor="#e9e9e9">
<font>audio only conversion</font>
</tr>
<tr>
<td>
Audio only conversion is also possible with
<i>transcode</i>.
Certainly, there are tons of tools out there, doing the
same job, so I will concentrate on useful examples, mainly
DVD ripping and encoding on the fly, using options "-p"
for input and "-m" for output.
<a name=aud_1><h3>audio track -> MP3</h3></a>
Some DVDs have a separate AC3 (Dobly Digital) film soundtrack, which
you might want to convert to MP3. Music DVDs have
tracks with uncompressed audio
which is LPCM format (linear PCM), you want to archive. In this
particular case, you might need to add "-d" for audio byte swapping.
You need to check with tcprobe which audio track is the
right one.
We do it in 1 step for
track 2 and write to the file "track.mp3":
<p>
<table>
<tr>
<td align=left valign="top" bgcolor="#ccffcc">
transcode</td>
<td align=left valign="top" bgcolor="#ccffcc">
-p /dev/dvd/ -T 1,-1 -a 2 </td>
</tr>
<td></td><td align=left valign="top" bgcolor="#ccffcc">
-y raw -m track.mp3 </td></tr>
</table>
<p>
<a name=aud_2><h3>audio track -> PCM</h3></a>
If you prefer uncompressed PCM data for further processing, add
"-N 0x1" in the command above:
<p>
<table>
<tr>
<td align=left valign="top" bgcolor="#ccffcc">
transcode</td>
<td align=left valign="top" bgcolor="#ccffcc">
-p /dev/dvd/ -T 1,-1 -a 2</td>
</tr>
<td></td><td align=left valign="top" bgcolor="#ccffcc">
-y raw -m track.pcm -N 0x1</td></tr>
</table>
<p>
<a name=aud_3><h3>ASF audio -> MP3</h3></a>
I had this ASF (advanced stream format) Genesis audio file
lying around and tried the <i>avifile</i> import module. Since
no auto-probing is available for ASF streams in the current
version, you must play around with the sample rate. CD quality
is 44100 Hz samplerate:
<p>
<table>
<tr>
<td align=left valign="top" bgcolor="#ccffcc">
transcode</td>
<td align=left valign="top" bgcolor="#ccffcc">
-p carpet_crawler_1999.asf -x null,af6</td>
</tr>
<tr><td></td>
<td align=left valign="top" bgcolor="#ccffcc">
-e 44100 -E 44100 -b 112</td>
</tr>
<td></td><td align=left valign="top" bgcolor="#ccffcc">
-y null,raw -m carpet_crawler_1999.mp3</td></tr>
</table>
<p>
</table>
</table>
<a name=maudio></a>
<table cellspacing="10" cellpadding="0" border="0" width="100%">
<tr>
<td align=left valign="top" width=30% bgcolor="#a0a0a0">
<table border="0" cellpadding="10" cellspacing="3" font size=+2 bgcolor="#ffffff" width=100%>
<td align="left" bgcolor="#e9e9e9">
<font>AVI-files with multiple audio tracks</font>
</tr>
<tr>
<td>
<a name=xvcd><h3>HowTo:</h3></a>
Before you start, try to find the best bitrate for video
encoding
with multiple audio tracks by using <i>tcprobe</i> with
option "-b n*128", for example, if you want n MP3 audio
tracks with 128kbps bitrate each.<br>
A first session produces the file movie.avi with a single audio
track "-a 0". Now, we use a similar command to extract a second
audio
track from the source. Suppose, we used the example modules
"vmod,amod"
for video and audio extraction.<p>
The second session goes as follows. This session will be much
faster, since no video is de/encoded.<p>
<Ul>
<li>
(1) transcode the second audio track "-a 1" into an AVI
container file named add-on.avi This looks like:
<table>
<tr>
<td align=left valign="top" bgcolor="#ccffcc">
transcode -i (...) -x null,amod -g 0x0 -y raw -a 1
-o add-on.avi -u 50 </tr>
</table>
<p>
The resulting file is only a temporary file but enables
proper processing with <i>avimerge</i>. The export
module "-y raw" is fine, since it writes proper (0 bytes)
video frames.
Set video import module to "null". If all goes well,
both files should be identical with respect to the number
of frames. Choose the proper audio track with "-a". Try also to
increase the internal buffers "-u" for speedup.<p>
<li>(2) merge this track into movie.avi
<table>
<tr>
<td align=left valign="top" bgcolor="#ccffcc">
avimerge -i movie.avi -o dualaudiomovie.avi -p add-on.avi
</tr>
</table>
<p>
<li> (3) Repeat steps (1-2) for even more audio tracks, if you
wish.
For best results, I recommend doing this procedure with a single
AVI movie file. All <i>avi*</i> post-processing tools now support
multiple audio tracks.<p>
--- <br>
Note: <i>transcode</i> supports reading from multiple-audio tracks
but only writes (exports) to single audio/video AVI-files.
</table>
</table>
<!-- hhmts start -->
Last modified: Thu May 16 12:59:16 CEST 2002
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