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diff --git a/DOCS/xml/en/encoding-guide.xml b/DOCS/xml/en/encoding-guide.xml index 9309df9df7..d458f31b1c 100644 --- a/DOCS/xml/en/encoding-guide.xml +++ b/DOCS/xml/en/encoding-guide.xml @@ -3,5550 +3,7 @@ <chapter id="encoding-guide"> <title>Encoding with <application>MEncoder</application></title> -<sect1 id="menc-feat-dvd-mpeg4"> -<title>Making a high quality MPEG-4 ("DivX") - rip of a DVD movie</title> - -<para> -One frequently asked question is "How do I make the highest quality rip -for a given size?". Another question is "How do I make the highest -quality DVD rip possible? I do not care about file size, I just want the best -quality." -</para> - -<para> -The latter question is perhaps at least somewhat wrongly posed. After all, if -you do not care about file size, why not simply copy the entire MPEG-2 video -stream from the the DVD? Sure, your AVI will end up being 5GB, give -or take, but if you want the best quality and do not care about size, -this is certainly your best option. -</para> - -<para> -In fact, the reason you want to transcode a DVD into MPEG-4 is -specifically because you <emphasis role="bold">do</emphasis> care about -file size. -</para> - -<para> -It is difficult to offer a cookbook recipe on how to create a very high -quality DVD rip. There are several factors to consider, and you should -understand these details or else you are likely to end up disappointed -with your results. Below we will investigate some of these issues, and -then have a look at an example. We assume you are using -<systemitem class="library">libavcodec</systemitem> to encode the video, -although the theory applies to other codecs as well. -</para> - -<para> -If this seems to be too much for you, you should probably use one of the -many fine frontends that are listed in the -<ulink url="http://www.mplayerhq.hu/design7/projects.html#mencoder_frontends">MEncoder section</ulink> -of our related projects page. -That way, you should be able to achieve high quality rips without too much -thinking, because most of those tools are designed to take clever decisions -for you. -</para> - -<!-- ********** --> - -<sect2 id="menc-feat-dvd-mpeg4-preparing-encode"> -<title>Preparing to encode: Identifying source material and framerate</title> - -<para> -Before you even think about encoding a movie, you need to take -several preliminary steps. -</para> - -<para> -The first and most important step before you encode should be -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, 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. -Experience shows that NTSC material is a lot more difficult to encode, -because there more elements to identify in the source. -In order to produce a suitable encode, you need to know the original -format. -Failure to take this into account will result in various flaws in your -encode, including ugly combing (interlacing) artifacts and duplicated -or even lost frames. -Besides being ugly, the artifacts also harm coding efficiency: -You will get worse quality per unit bitrate. -</para> - - -<sect3 id="menc-feat-dvd-mpeg4-preparing-encode-fps"> -<title>Identifying source framerate</title> - -<para> -Here is a list of common types of source material, where you are -likely to find them, and their properties: -</para> - -<itemizedlist> -<listitem><para> - <emphasis role="bold">Standard Film</emphasis>: Produced for - theatrical display at 24fps. -</para></listitem> -<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 odd- or even-numbered lines of a - frame. - Television was designed to refresh these in alternation as a - cheap form of analog compression. - The human eye supposedly compensates for this, but once you - understand interlacing you will learn to see it on TV too and - never enjoy TV again. - Two fields do <emphasis role="bold">not</emphasis> make a - complete frame, because they are captured 1/50 of a second apart - in time, and thus they do not line up unless there is no motion. -</para></listitem> -<listitem><para> - <emphasis role="bold">NTSC Video</emphasis>: Recorded with an - NTSC video camera at 60000/1001 fields per second, or 60 fields per - second in the pre-color era. - Otherwise similar to PAL. -</para></listitem> -<listitem><para> - <emphasis role="bold">Animation</emphasis>: Usually drawn at - 24fps, but also comes in mixed-framerate varieties. -</para></listitem> -<listitem><para> - <emphasis role="bold">Computer Graphics (CG)</emphasis>: Can be - any framerate, but some are more common than others; 24 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 - framerates. -</para></listitem> -</itemizedlist> -</sect3> - - -<sect3 id="menc-feat-dvd-mpeg4-preparing-encode-material"> -<title>Identifying source material</title> - -<para> -Movies consisting of frames are referred to as progressive, -while those consisting of independent fields are called -either interlaced or video - though this latter term is -ambiguous. -</para> - -<para> -To further complicate matters, some movies will be a mix of -several of the above. -</para> - -<para> -The most important distinction to make between all of these -formats is that some are frame-based, while others are -field-based. -<emphasis role="bold">Whenever</emphasis> a movie is prepared -for display on television (including DVD), it is converted to a -field-based format. -The various methods by which this can be done are collectively -referred to as "telecine", of which the infamous NTSC -"3:2 pulldown" is one variety. -Unless the original material was also field-based (and the same -fieldrate), you are getting the movie in a format other than the -original. -</para> - -<itemizedlist> -<title>There are several common types of pulldown:</title> -<listitem><para> - <emphasis role="bold">PAL 2:2 pulldown</emphasis>: The nicest of - them all. - 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 the duration of three fields, instead of - just two. - This avoids the 4% speedup issue, but makes the process much - more difficult to reverse. - It is usually seen in musical productions where adjusting the - speed by 4% would seriously damage the musical score. -</para></listitem> -<listitem><para> - <emphasis role="bold">NTSC 3:2 telecine</emphasis>: Frames are - 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 60000/1001 fields per second to maintain NTSC fieldrate. -</para></listitem> -<listitem><para> - <emphasis role="bold">NTSC 2:2 pulldown</emphasis>: Used for - showing 30fps material on NTSC. - Nice, just like 2:2 PAL pulldown. -</para></listitem> -</itemizedlist> - -<para> -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. -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 both to encode the original progressive frames and to store -the number of fields for which a frame should be shown in the -header of that frame. -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 but instead produce movies with -"hard telecine", where fields are actually duplicated in the -encoded MPEG-2. -</para> - -<para> -The procedures for dealing with these cases will be covered -<link linkend="menc-feat-telecine">later in this guide</link>. -For now, we leave you with some guides to identifying which type -of material you are dealing with: -</para> - -<itemizedlist> -<title>NTSC regions:</title> -<listitem><para> - If <application>MPlayer</application> prints that the framerate - has changed to 24000/1001 when watching your movie, and never changes - back, it is almost certainly progressive content that has been - "soft telecined". -</para></listitem> -<listitem><para> - If <application>MPlayer</application> shows the framerate - switching back and forth between 24000/1001 and 30000/1001, and you see - "combing" at times, then there are several possibilities. - The 24000/1001 fps segments are almost certainly progressive - content, "soft telecined", but the 30000/1001 fps parts could be - either hard-telecined 24000/1001 fps content or 60000/1001 fields per second - NTSC video. - Use the same guidelines as the following two cases to determine which. -</para></listitem> -<listitem><para> - If <application>MPlayer</application> never shows the framerate - changing, and every single frame with motion appears combed, your - movie is NTSC video at 60000/1001 fields per second. -</para></listitem> -<listitem><para> - If <application>MPlayer</application> never shows the framerate - changing, and two frames out of every five appear combed, your - movie is "hard telecined" 24000/1001fps content. -</para></listitem> -</itemizedlist> - -<itemizedlist> -<title>PAL regions:</title> -<listitem><para> - If you never see any combing, your movie is 2:2 pulldown. -</para></listitem> -<listitem><para> - If you see combing alternating in and out every half second, - then your movie is 2:2:2:2:2:2:2:2:2:2:2:3 pulldown. -</para></listitem> -<listitem><para> - If you always see combing during motion, then your movie is PAL - video at 50 fields per second. -</para></listitem> -</itemizedlist> - -<note><title>Hint:</title> -<para> - <application>MPlayer</application> can slow down movie playback - with the -speed option or play it frame-by-frame. - Try using <option>-speed</option> 0.2 to watch the movie very - slowly or press the "<keycap>.</keycap>" key repeatedly to play one frame at - a time and identify the pattern, if you cannot see it at full speed. -</para> -</note> -</sect3> -</sect2> - -<!-- ********** --> - -<sect2 id="menc-feat-dvd-mpeg4-2pass"> -<title>Constant quantizer vs. multipass</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. -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 multipass (ABR, or average bitrate). -</para> - -<para> -The complexity of the frames of a movie, and thus the number of bits -required to compress them, can vary greatly from one scene to another. -Modern video encoders can adjust to these needs as they go and vary -the bitrate. -In simple modes such as CBR, however, the encoders do not know the -bitrate needs of future scenes and so cannot exceed the requested -average bitrate for long stretches of time. -More advanced modes, such as multipass encode, can take into account -the statistics from previous passes; this fixes the problem mentioned -above. -</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>, -<systemitem class="library">Xvid</systemitem> -and <systemitem class="library">libavcodec</systemitem> support -multipass, which slightly improves quality at each pass, -yet this improvement is no longer measurable nor noticeable after the -4th or so pass. -Therefore, in this section, two pass and multipass will be used -interchangeably. -</para> -</note> - -<para> -In each of these modes, the video codec (such as -<systemitem class="library">libavcodec</systemitem>) -breaks the video frame into 16x16 pixel macroblocks and then applies a -quantizer to each macroblock. The lower the quantizer, the better the -quality and higher the bitrate. -The method the movie encoder uses to determine -which quantizer to use for a given macroblock varies and is highly -tunable. (This is an extreme over-simplification of the actual -process, but the basic concept is useful to understand.) -</para> - -<para> -When you specify a constant bitrate, the video codec will encode the video, -discarding -detail as much as necessary and as little as possible in order to remain -lower than the given bitrate. If you truly do not care about file size, -you could as well use CBR and specify a bitrate of infinity. (In -practice, this means a value high enough so that it poses no limit, like -10000Kbit.) With no real restriction on bitrate, the result is that -the codec will use the lowest -possible quantizer for each macroblock (as specified by -<option>vqmin</option> for -<systemitem class="library">libavcodec</systemitem>, which is 2 by default). -As soon as you specify a -low enough bitrate that the codec -is forced to use a higher quantizer, then you are almost certainly ruining -the quality of your video. -In order to avoid that, you should probably downscale your video, according -to the method described later on in this guide. -In general, you should avoid CBR altogether if you care about quality. -</para> - -<para> -With constant quantizer, the codec uses the same quantizer, as -specified by the <option>vqscale</option> option (for -<systemitem class="library">libavcodec</systemitem>), on every macroblock. -If you want the highest quality rip possible, again ignoring bitrate, -you can use <option>vqscale=2</option>. -This will yield the same bitrate and PSNR (peak signal-to-noise ratio) -as CBR with -<option>vbitrate</option>=infinity and the default <option>vqmin</option> -of 2. -</para> - -<para> -The problem with constant quantizing is that it uses the given quantizer -whether the macroblock needs it or not. That is, it might be possible -to use a higher quantizer on a macroblock without sacrificing visual -quality. Why waste the bits on an unnecessarily low quantizer? Your -CPU has as many cycles as there is time, but there is only so many bits -on your hard disk. -</para> - -<para> -With a two pass encode, the first pass will rip the movie as though it -were CBR, but it will keep a log of properties for each frame. This -data is then used during the second pass in order to make intelligent -decisions about which quantizers to use. During fast action or high -detail scenes, higher quantizers will likely be used, and during -slow moving or low detail scenes, lower quantizers will be used. -Normally, the amount of motion is much more important than the -amount of detail. -</para> - -<para> -If you use <option>vqscale=2</option>, then you are wasting bits. If you -use <option>vqscale=3</option>, then you are not getting the highest -quality rip. Suppose you rip a DVD at <option>vqscale=3</option>, and -the result is 1800Kbit. If you do a two pass encode with -<option>vbitrate=1800</option>, the resulting video will have -<emphasis role="bold">higher quality</emphasis> for the -<emphasis role="bold">same bitrate</emphasis>. -</para> - -<para> -Since you are now convinced that two pass is the way to go, the real -question now is what bitrate to use? The answer is that there is no -single answer. Ideally you want to choose a bitrate that yields the -best balance between quality and file size. This is going to vary -depending on the source video. -</para> - -<para> -If size does not matter, a good starting point for a very high quality -rip is about 2000Kbit plus or minus 200Kbit. -For fast action or high detail source video, or if you just have a very -critical eye, you might decide on 2400 or 2600. -For some DVDs, you might not notice a difference at 1400Kbit. It is a -good idea to experiment with scenes at different bitrates to get a feel. -</para> - -<para> -If you aim at a certain size, you will have to somehow calculate the bitrate. -But before that, you need to know how much space you should reserve for the -audio track(s), so you should -<link linkend="menc-feat-dvd-mpeg4-audio">rip those</link> first. -You can compute the bitrate with the following equation: -<systemitem>bitrate = (target_size_in_Mbytes - sound_size_in_Mbytes) * -1024 * 1024 / length_in_secs * 8 / 1000</systemitem> -For instance, to squeeze a two-hour movie onto a 702MB CD, with 60MB -of audio track, the video bitrate will have to be: -<systemitem>(702 - 60) * 1024 * 1024 / (120*60) * 8 / 1000 -= 740kbps</systemitem> -</para> -</sect2> - -<!-- ********** --> - -<sect2 id="menc-feat-dvd-mpeg4-constraints"> -<title>Constraints for efficient encoding</title> - -<para> -Due to the nature of MPEG-type compression, there are various -constraints you should follow for maximal quality. -MPEG splits the video up into 16x16 squares called macroblocks, -each composed of 4 8x8 blocks of luma (intensity) information and two -half-resolution 8x8 chroma (color) blocks (one for red-cyan axis and -the other for the blue-yellow axis). -Even if your movie width and height are not multiples of 16, the -encoder will use enough 16x16 macroblocks to cover the whole picture -area, and the extra space will go to waste. -So in the interests of maximizing quality at a fixed file size, it is -a bad idea to use dimensions that are not multiples of 16. -</para> - -<para> -Most DVDs also have some degree of black borders at the edges. Leaving -these in place will hurt quality <emphasis role="bold">a lot</emphasis> -in several ways. -</para> - -<orderedlist> -<listitem> - <para> - MPEG-type compression is highly dependent on frequency domain - transformations, in particular the Discrete Cosine Transform (DCT), - which is similar to the Fourier transform. This sort of encoding is - efficient for representing patterns and smooth transitions, but it - has a hard time with sharp edges. In order to encode them it must - use many more bits, or else an artifact known as ringing will - appear. - </para> - - <para> - The frequency transform (DCT) takes place separately on each - macroblock (actually each block), so this problem only applies when - the sharp edge is inside a block. If your black borders begin - exactly at multiple-of-16 pixel boundaries, this is not a problem. - However, the black borders on DVDs rarely come nicely aligned, so - in practice you will always need to crop to avoid this penalty. - </para> -</listitem> -</orderedlist> - -<para> -In addition to frequency domain transforms, MPEG-type compression uses -motion vectors to represent the change from one frame to the next. -Motion vectors naturally work much less efficiently for new content -coming in from the edges of the picture, because it is not present in -the previous frame. As long as the picture extends all the way to the -edge of the encoded region, motion vectors have no problem with -content moving out the edges of the picture. However, in the presence -of black borders, there can be trouble: -</para> - -<orderedlist continuation="continues"> -<listitem> - <para> - For each macroblock, MPEG-type compression stores a vector - identifying which part of the previous frame should be copied into - this macroblock as a base for predicting the next frame. Only the - remaining differences need to be encoded. If a macroblock spans the - edge of the picture and contains part of the black border, then - motion vectors from other parts of the picture will overwrite the - black border. This means that lots of bits must be spent either - re-blackening the border that was overwritten, or (more likely) a - motion vector will not be used at all and all the changes in this - macroblock will have to be coded explicitly. Either way, encoding - efficiency is greatly reduced. - </para> - - <para> - Again, this problem only applies if black borders do not line up on - multiple-of-16 boundaries. - </para> -</listitem> - -<listitem> - <para> - Finally, suppose we have a macroblock in the interior of the - picture, and an object is moving into this block from near the edge - of the image. MPEG-type coding cannot say "copy the part that is - inside the picture but not the black border." So the black border - will get copied inside too, and lots of bits will have to be spent - encoding the part of the picture that is supposed to be there. - </para> - - <para> - If the picture runs all the way to the edge of the encoded area, - MPEG has special optimizations to repeatedly copy the pixels at the - edge of the picture when a motion vector comes from outside the - encoded area. This feature becomes useless when the movie has black - borders. Unlike problems 1 and 2, aligning the borders at multiples - of 16 does not help here. - </para> -</listitem> - -<listitem><para> - Despite the borders being entirely black and never changing, there - is at least a minimal amount of overhead involved in having more - macroblocks. -</para></listitem> -</orderedlist> - -<para> -For all of these reasons, it is recommended to fully crop black -borders. Further, if there is an area of noise/distortion at the edge -of the picture, cropping this will improve encoding efficiency as -well. Videophile purists who want to preserve the original as close as -possible may object to this cropping, but unless you plan to encode at -constant quantizer, the quality you gain from cropping will -considerably exceed the amount of information lost at the edges. -</para> -</sect2> - -<!-- ********** --> - -<sect2 id="menc-feat-dvd-mpeg4-crop"> -<title>Cropping and Scaling</title> - -<para> -Recall from the previous section that the final picture size you -encode should be a multiple of 16 (in both width and height). -This can be achieved by cropping, scaling, or a combination of both. -</para> - -<para> -When cropping, there are a few guidelines that must be followed to -avoid damaging your movie. -The normal YUV format, 4:2:0, stores chroma (color) information -subsampled, i.e. chroma is only sampled half as often in each -direction as luma (intensity) information. -Observe this diagram, where L indicates luma sampling points and C -chroma. -</para> - -<informaltable> -<?dbhtml table-width="40%" ?> -<?dbfo table-width="40%" ?> -<tgroup cols="8" align="center"> -<colspec colnum="1" colname="col1"/> -<colspec colnum="2" colname="col2"/> -<colspec colnum="3" colname="col3"/> -<colspec colnum="4" colname="col4"/> -<colspec colnum="5" colname="col5"/> -<colspec colnum="6" colname="col6"/> -<colspec colnum="7" colname="col7"/> -<colspec colnum="8" colname="col8"/> -<spanspec spanname="spa1-2" namest="col1" nameend="col2"/> -<spanspec spanname="spa3-4" namest="col3" nameend="col4"/> -<spanspec spanname="spa5-6" namest="col5" nameend="col6"/> -<spanspec spanname="spa7-8" namest="col7" nameend="col8"/> - <tbody> - <row> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - </row> - <row> - <entry spanname="spa1-2">C</entry> - <entry spanname="spa3-4">C</entry> - <entry spanname="spa5-6">C</entry> - <entry spanname="spa7-8">C</entry> - </row> - <row> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - </row> - <row> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - </row> - <row> - <entry spanname="spa1-2">C</entry> - <entry spanname="spa3-4">C</entry> - <entry spanname="spa5-6">C</entry> - <entry spanname="spa7-8">C</entry> - </row> - <row> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - </row> - </tbody> -</tgroup> -</informaltable> - -<para> -As you can see, rows and columns of the image naturally come in pairs. -Thus your crop offsets and dimensions <emphasis>must</emphasis> be -even numbers. -If they are not, the chroma will no longer line up correctly with the -luma. -In theory, it is possible to crop with odd offsets, but it requires -resampling the chroma which is potentially a lossy operation and not -supported by the crop filter. -</para> - -<para> -Further, interlaced video is sampled as follows: -</para> - -<informaltable> -<?dbhtml table-width="80%" ?> -<?dbfo table-width="80%" ?> -<tgroup cols="16" align="center"> -<colspec colnum="1" colname="col1"/> -<colspec colnum="2" colname="col2"/> -<colspec colnum="3" colname="col3"/> -<colspec colnum="4" colname="col4"/> -<colspec colnum="5" colname="col5"/> -<colspec colnum="6" colname="col6"/> -<colspec colnum="7" colname="col7"/> -<colspec colnum="8" colname="col8"/> -<colspec colnum="9" colname="col9"/> -<colspec colnum="10" colname="col10"/> -<colspec colnum="11" colname="col11"/> -<colspec colnum="12" colname="col12"/> -<colspec colnum="13" colname="col13"/> -<colspec colnum="14" colname="col14"/> -<colspec colnum="15" colname="col15"/> -<colspec colnum="16" colname="col16"/> -<spanspec spanname="spa1-2" namest="col1" nameend="col2"/> -<spanspec spanname="spa3-4" namest="col3" nameend="col4"/> -<spanspec spanname="spa5-6" namest="col5" nameend="col6"/> -<spanspec spanname="spa7-8" namest="col7" nameend="col8"/> -<spanspec spanname="spa9-10" namest="col9" nameend="col10"/> -<spanspec spanname="spa11-12" namest="col11" nameend="col12"/> -<spanspec spanname="spa13-14" namest="col13" nameend="col14"/> -<spanspec spanname="spa15-16" namest="col15" nameend="col16"/> - <tbody> - <row> - <entry namest="col1" nameend="col8">Top field</entry> - <entry namest="col9" nameend="col16">Bottom field</entry> - </row> - <row> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - </row> - <row> - <entry spanname="spa1-2">C</entry> - <entry spanname="spa3-4">C</entry> - <entry spanname="spa5-6">C</entry> - <entry spanname="spa7-8">C</entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - </row> - <row> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - </row> - <row> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - </row> - <row> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry spanname="spa9-10">C</entry> - <entry spanname="spa11-12">C</entry> - <entry spanname="spa13-14">C</entry> - <entry spanname="spa15-16">C</entry> - </row> - <row> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - </row> - <row> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - </row> - <row> - <entry spanname="spa1-2">C</entry> - <entry spanname="spa3-4">C</entry> - <entry spanname="spa5-6">C</entry> - <entry spanname="spa7-8">C</entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - </row> - <row> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - </row> - <row> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - </row> - <row> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry spanname="spa9-10">C</entry> - <entry spanname="spa11-12">C</entry> - <entry spanname="spa13-14">C</entry> - <entry spanname="spa15-16">C</entry> - </row> - <row> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry></entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - <entry>L</entry> - </row> - </tbody> -</tgroup> -</informaltable> - -<para> -As you can see, the pattern does not repeat until after 4 lines. -So for interlaced video, your y-offset and height for cropping must -be multiples of 4. -</para> - -<para> -Native DVD resolution is 720x480 for NTSC, and 720x576 for PAL, but -there is an aspect flag that specifies whether it is full-screen (4:3) or -wide-screen (16:9). Many (if not most) widescreen DVDs are not strictly -16:9, and will be either 1.85:1 or 2.35:1 (cinescope). This means that -there will be black bands in the video that will need to be cropped out. -</para> - -<para> -<applicat |