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mirror of https://github.com/mpv-player/mpv synced 2025-03-25 04:38:01 +00:00

Nits and corrections suggested by The Wanderer

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@15468 b3059339-0415-0410-9bf9-f77b7e298cf2
This commit is contained in:
gpoirier 2005-05-14 15:44:52 +00:00
parent bc06bb6c1d
commit edee61232e

View File

@ -531,8 +531,8 @@ vcodec=mpeg2video:intra_matrix=8,9,12,22,26,27,29,34,9,10,14,26,27,29,34,37,
determining what type of content you are dealing with.
If your source material comes from DVD or broadcast/cable/satellite
TV, it will be stored in one of two formats: NTSC for North
America and Japan, and PAL for Europe, etc.
But it is important to realize that this is just the formatting for
America and Japan, PAL for Europe, etc.
It is important to realize, however, that this is just the formatting for
presentation on a television, and often does
<emphasis role="bold">not</emphasis> correspond to the
original format of the movie.
@ -558,7 +558,7 @@ vcodec=mpeg2video:intra_matrix=8,9,12,22,26,27,29,34,9,10,14,26,27,29,34,37,
<listitem><para>
<emphasis role="bold">PAL video</emphasis>: Recorded with a PAL
video camera at 50 fields per second.
A field consists of just the even or odd numbered lines of a
A field consists of just the odd- or even-numbered lines of a
frame.
Television was designed to refresh these in alternation as a
cheap form of analog compression.
@ -577,12 +577,13 @@ vcodec=mpeg2video:intra_matrix=8,9,12,22,26,27,29,34,9,10,14,26,27,29,34,37,
</para></listitem>
<listitem><para>
<emphasis role="bold">Animation</emphasis>: Usually drawn at
24fps, but animation also comes in mixed-framerate varieties.
24fps, but also comes in mixed-framerate varieties.
</para></listitem>
<listitem><para>
<emphasis role="bold">Computer Graphics (CG)</emphasis>: Can be
any framerate, but 24 and 30 fps are the most frequently
encountered in NTSC regions, and 25 fps in PAL regions.
any framerate, but some are more common than others; 23 and
30 frames per second are typical for NTSC, and 25fps is typical
for PAL.
</para></listitem>
<listitem><para>
<emphasis role="bold">Old Film</emphasis>: Various lower
@ -596,7 +597,7 @@ vcodec=mpeg2video:intra_matrix=8,9,12,22,26,27,29,34,9,10,14,26,27,29,34,37,
<para>
Movies consisting of frames are referred to as progressive,
while those consisting of independent fields are called
interlaced, or sometimes video, although this latter term is
either interlaced or video - though this latter term is
ambiguous.
</para>
<para>
@ -623,14 +624,14 @@ vcodec=mpeg2video:intra_matrix=8,9,12,22,26,27,29,34,9,10,14,26,27,29,34,37,
<listitem><para>
<emphasis role="bold">PAL 2:2 pulldown</emphasis>: The nicest of
them all.
Each frame is shown for two fields duration, by extracting the
Each frame is shown for the duration of two fields, by extracting the
even and odd lines and showing them in alternation.
If the original material is 24fps, this process speeds up the
movie by 4%.
</para></listitem>
<listitem><para>
<emphasis role="bold">PAL 2:2:2:2:2:2:2:2:2:2:2:3 pulldown</emphasis>:
Every 12th frame is shown for three fields duration, instead of
Every 12th frame is shown for the duration of three fields, instead of
just two.
This avoids the 4% speedup issue, but makes the process much
more difficult to reverse.
@ -639,8 +640,8 @@ vcodec=mpeg2video:intra_matrix=8,9,12,22,26,27,29,34,9,10,14,26,27,29,34,37,
</para></listitem>
<listitem><para>
<emphasis role="bold">NTSC 3:2 telecine</emphasis>: Frames are
shown alternatively for 3 fields or 2 fields duration.
This gives a fieldrate 5/2 times the original framerate.
shown alternately for the duration of 3 fields or 2 fields.
This gives a fieldrate 2.5 times the original framerate.
The result is also slowed down very slightly from 60 fields per
second to 59.94 fields per second to maintain NTSC fieldrate.
</para></listitem>
@ -652,30 +653,31 @@ vcodec=mpeg2video:intra_matrix=8,9,12,22,26,27,29,34,9,10,14,26,27,29,34,37,
</itemizedlist>
<para>
There are also methods for converting between NTSC and PAL video.
Such topics are beyond the scope of this guide.
There are also methods for converting between NTSC and PAL video,
but such topics are beyond the scope of this guide.
If you encounter such a movie and want to encode it, your best
bet is to find a copy in the original format.
NTSC/PAL conversion is highly destructive and cannot be reversed
cleanly, so your encode will greatly suffer if it is made from a
converted source.
Conversion between these two formats is highly destructive and
cannot be reversed cleanly, so your encode will greatly suffer
if it is made from a converted source.
</para>
<para>
When video is stored on DVD, consecutive pairs of fields are
grouped as a frame, even though they are not intended to be shown
at the same moment in time.
The MPEG-2 standard used on DVD and digital TV provides a way to
encode the original progressive frames, and store the number of
fields for which each should be shown in the frame headers.
If this method has been used, the term "soft telecine" will often
be used to describe the movie, since the process only directs the
The MPEG-2 standard used on DVD and digital TV provides both a
way to encode the original progressive frames, and to store in
the header of each frame the number of fields for which it should
be shown.
If this method has been used, the movie will often be described
as "soft-telecined", since the process only directs the
DVD player to apply pulldown to the movie rather than altering
the movie itself.
This case is highly preferable since it can easily be reversed
(actually ignored) by the encoder, and since it preserves maximal
quality.
However, many DVD and broadcast production studios do not use
proper encoding techniques, and instead produce movies with
proper encoding techniques but instead produce movies with
"hard telecine", where fields are actually duplicated in the
encoded MPEG-2.
</para>
@ -706,14 +708,13 @@ vcodec=mpeg2video:intra_matrix=8,9,12,22,26,27,29,34,9,10,14,26,27,29,34,37,
</para></listitem>
<listitem><para>
If <application>MPlayer</application> never shows the framerate
change, and every single frame with motion appears combed, your
changing, and every single frame with motion appears combed, your
movie is NTSC video at 59.94 fields per second.
</para></listitem>
<listitem><para>
If <application>MPlayer</application> never shows the framerate
change, and two frames out of every five appear combed, your
movie is "hard telecined"
24fps content.
movie is "hard telecined" 24fps content.
</para></listitem>
</itemizedlist>
@ -744,22 +745,34 @@ vcodec=mpeg2video:intra_matrix=8,9,12,22,26,27,29,34,9,10,14,26,27,29,34,37,
</sect2>
<sect2 id="menc-feat-dvd-mpeg4-2pass">
<title>Constant Quantizer vs. two pass</title>
<title>Constant quantizer vs. multi-pass</title>
<para>
It is possible to encode your movie at a wide range of qualities.
With modern video encoders and a bit of pre-codec compression
(downscaling and denoising), it is possible to achieve very good
quality at 700 MB, for a 90-110 minute widescreen movie.
And all but the longest movies can be encoded with near-perfect
Furthermore, all but the longest movies can be encoded with near-perfect
quality at 1400 MB.
</para>
<para>
There are three approaches to encoding the video: constant bitrate
(CBR), constant quantizer, and two pass (ABR, or average bitrate).
(CBR), constant quantizer, and multi-pass (ABR, or average bitrate).
</para>
<note><title>Note:</title>
<para>
Most codecs which support ABR encode only support two pass encode
while some others such as <systemitem class="library">x264</systemitem>
and <systemitem class="library">libavcodec</systemitem> support
multi-pass, which slightly improves quality at each pass,
yet this improvement is no longer noticeable after the 6th or so pass.
Therefore, in this section, two pass and multi-pass will be used
interchangeably.
</para>
</note>
<para>
In each of these modes, <systemitem class="library">libavcodec</systemitem>
breaks the video frame into 16x16 pixel macroblocks and then applies a
@ -1596,8 +1609,8 @@ vcodec=mpeg2video:intra_matrix=8,9,12,22,26,27,29,34,9,10,14,26,27,29,34,37,
deinterlace or not.
While deinterlacing will make your movie usable on progressive
scan displays such a computer monitors and projectors, it comes
at a cost: The field rate of 50 or 59.94 fields per second
is halved to 25 or 29.97 frames per second, and roughly half
at a cost: The fieldrate of 50 or 59.94 fields per second
is halved to 25 or 29.97 frames per second, and roughly half of
the information in your movie will be lost during scenes with
significant motion.
</para>