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