mirror of https://github.com/mpv-player/mpv
Moves the "audio" section just before the "muxing" section. + fixes suggested by Jeff
git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@16087 b3059339-0415-0410-9bf9-f77b7e298cf2
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@ -972,7 +972,7 @@
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change the bitrate as well!.
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</para>
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<para>
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Bitrate does <emphasis role="bold">not</emphasis> scale proportional
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Bitrate does <emphasis role="bold">not</emphasis> scale proportionally
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to resolution.
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That is to say, a 320x240 file at 200 kbit/sec will not be the same
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quality as the same movie at 640x480 and 800 kbit/sec!
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@ -1010,7 +1010,7 @@
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rigor.
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Further, given that movies vary greatly with regard to noise, detail,
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degree of motion, etc., it's futile to make general recommendations
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for bits per length-of-diagonal (the analogue of bits per pixel,
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for bits per length-of-diagonal (the analog of bits per pixel,
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using the square root).
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</para>
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<para>
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@ -1082,70 +1082,39 @@
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</sect2>
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<sect2 id="menc-feat-dvd-mpeg4-audio">
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<title>Audio</title>
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<sect2 id="menc-feat-dvd-mpeg4-filtering">
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<title>Filtering</title>
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<para>
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Audio is a much simpler problem to solve: if you care about quality, just
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leave it as is.
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Even AC3 5.1 streams are at most 448Kbit/s, and they are worth every bit.
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You might be tempted to transcode the audio to high quality Vorbis, but
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just because you do not have an A/V receiver for AC3 pass-through today
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does not mean you will not have one tomorrow. Future-proof your DVD rips by
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preserving the AC3 stream.
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You can keep the AC3 stream either by copying it directly into the video
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stream <link linkend="menc-feat-mpeg4">during the encoding</link>.
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You can also extract the AC3 stream in order to mux it into containers such
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as NUT or Matroska.
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<screen>mplayer <replaceable>source_file.vob</replaceable> -aid 129 -dumpaudio -dumpfile <replaceable>sound.ac3</replaceable></screen>
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will dump into the file <replaceable>sound.ac3</replaceable> the
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audio track number 129 from the file
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<replaceable>source_file.vob</replaceable> (NB: DVD VOB files
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usually use a different audio numbering,
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which means that the VOB audio track 129 is the 2nd audio track of the file).
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In general, you want to do as little filtering as possible to the movie
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in order to remain close to the original DVD source. Cropping is often
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necessary (as described above), but avoid to scale the video. Although
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scaling down is sometimes preferred to using higher quantizers, we want
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to avoid both these things: remember that we decided from the start to
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trade bits for quality.
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</para>
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<para>
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But sometimes you truly have no choice but to further compress the
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sound so that more bits can be spent on the video.
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Most people choose to compress audio with either MP3 or Vorbis audio
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codecs.
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While the latter is a very space-efficient codec, MP3 is better supported
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by hardware players, although this trend is changing.
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Also, do not adjust gamma, contrast, brightness, etc. What looks good
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on your display may not look good on others. These adjustments should
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be done on playback only.
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</para>
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<para>
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First of all, you will have to convert the DVD sound into a WAV file that the
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audio codec can use as input.
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For example:
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<screen>mplayer <replaceable>source_file.vob</replaceable> -ao pcm:file=<replaceable>destination_sound.wav</replaceable> -vc dummy -aid 1 -vo null</screen>
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will dump the second audio track from the file
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<replaceable>source_file.vob</replaceable> into the file
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<replaceable>destination_sound.wav</replaceable>.
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You may want to normalize the sound before encoding, as DVD audio tracks
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are commonly recorded at low volumes.
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You can use the tool <application>normalize</application> for instance,
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which is available in most distributions.
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If you are using Windows, a tool such as <application>BeSweet</application>
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can do the same job.
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You will compress in either Vorbis or MP3.
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For example:
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<screen>oggenc -q1 <replaceable>destination_sound.wav</replaceable></screen>
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will encode <replaceable>destination_sound.wav</replaceable> with
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the encoding quality 1, which is roughly equivalent to 80Kb/s, and
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is the minimum quality at which you should encode if you care about
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quality.
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Please note that MEncoder currently cannot mux Vorbis audio tracks
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into the output file because it only supports AVI and MPEG
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containers as an output, each of which may lead to audio/video
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playback synchronization problems with some players when the AVI file
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contain VBR audio streams such as Vorbis.
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Do not worry, this document will show you how you can do that with third
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party programs.
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One thing you might want to do, however, is pass the video through a
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very light denoise filter, such as <option>-vf hqdn3d=2:1:2</option>.
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Again, it is a matter of putting those bits to better use: why waste them
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encoding noise when you can just add that noise back in during playback?
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Increasing the parameters for <option>hqdn3d</option> will further
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improve compressibility, but if you increase the values too much, you
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risk degrading the image visibily. The suggested values above
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(<option>2:1:2</option>) are quite conservative; you should feel free to
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experiment with higher values and observe the results for yourself.
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</para>
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</sect2>
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<sect2 id="menc-feat-dvd-mpeg4-interlacing">
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<title>Interlacing and Telecine</title>
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@ -1254,34 +1223,67 @@ Note the <option>ilmv</option> and <option>ildct</option> options.
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</para>
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</sect2>
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<sect2 id="menc-feat-dvd-mpeg4-filtering">
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<title>Filtering</title>
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<sect2 id="menc-feat-dvd-mpeg4-audio">
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<title>Audio</title>
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<para>
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In general, you want to do as little filtering as possible to the movie
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in order to remain close to the original DVD source. Cropping is often
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necessary (as described above), but do not scale the video. Although
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scaling down is sometimes preferred to using higher quantizers, we want
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to avoid both these things: remember that we decided from the start to
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trade bits for quality.
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Audio is a much simpler problem to solve: if you care about quality, just
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leave it as is.
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Even AC3 5.1 streams are at most 448Kbit/s, and they are worth every bit.
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You might be tempted to transcode the audio to high quality Vorbis, but
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just because you do not have an A/V receiver for AC3 pass-through today
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does not mean you will not have one tomorrow. Future-proof your DVD rips by
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preserving the AC3 stream.
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You can keep the AC3 stream either by copying it directly into the video
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stream <link linkend="menc-feat-mpeg4">during the encoding</link>.
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You can also extract the AC3 stream in order to mux it into containers such
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as NUT or Matroska.
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<screen>mplayer <replaceable>source_file.vob</replaceable> -aid 129 -dumpaudio -dumpfile <replaceable>sound.ac3</replaceable></screen>
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will dump into the file <replaceable>sound.ac3</replaceable> the
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audio track number 129 from the file
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<replaceable>source_file.vob</replaceable> (NB: DVD VOB files
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usually use a different audio numbering,
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which means that the VOB audio track 129 is the 2nd audio track of the file).
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</para>
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<para>
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Also, do not adjust gamma, contrast, brightness, etc. What looks good
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on your display may not look good on others. These adjustments should
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be done on playback only.
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But sometimes you truly have no choice but to further compress the
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sound so that more bits can be spent on the video.
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Most people choose to compress audio with either MP3 or Vorbis audio
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codecs.
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While the latter is a very space-efficient codec, MP3 is better supported
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by hardware players, although this trend is changing.
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</para>
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<para>
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One thing you might want to do, however, is pass the video through a
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very light denoise filter, such as <option>-vf hqdn3d=2:1:2</option>.
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Again, it is a matter of putting those bits to better use: why waste them
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encoding noise when you can just add that noise back in during playback?
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Increasing the parameters for <option>hqdn3d</option> will further
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improve compressibility, but if you increase the values too much, you
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risk degrading the image visibily. The suggested values above
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(<option>2:1:2</option>) are quite conservative; you should feel free to
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experiment with higher values and observe the results for yourself.
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First of all, you will have to convert the DVD sound into a WAV file that the
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audio codec can use as input.
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For example:
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<screen>mplayer <replaceable>source_file.vob</replaceable> -ao pcm:file=<replaceable>destination_sound.wav</replaceable> -vc dummy -aid 1 -vo null</screen>
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will dump the second audio track from the file
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<replaceable>source_file.vob</replaceable> into the file
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<replaceable>destination_sound.wav</replaceable>.
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You may want to normalize the sound before encoding, as DVD audio tracks
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are commonly recorded at low volumes.
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You can use the tool <application>normalize</application> for instance,
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which is available in most distributions.
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If you are using Windows, a tool such as <application>BeSweet</application>
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can do the same job.
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You will compress in either Vorbis or MP3.
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For example:
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<screen>oggenc -q1 <replaceable>destination_sound.wav</replaceable></screen>
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will encode <replaceable>destination_sound.wav</replaceable> with
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the encoding quality 1, which is roughly equivalent to 80Kb/s, and
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is the minimum quality at which you should encode if you care about
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quality.
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Please note that MEncoder currently cannot mux Vorbis audio tracks
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into the output file because it only supports AVI and MPEG
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containers as an output, each of which may lead to audio/video
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playback synchronization problems with some players when the AVI file
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contain VBR audio streams such as Vorbis.
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Do not worry, this document will show you how you can do that with third
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party programs.
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</para>
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</sect2>
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|
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