Encoding with <application>MEncoder</application>

Encoding with <application>MEncoder</application> For the complete list of available MEncoder options and examples, please see the man page. For a series of hands-on examples and detailed guides on using several encoding parameters, read the encoding-tips that were collected from several mailing list threads on mplayer-users. Search the archives for a wealth of discussions about all aspects of and problems related to encoding with MEncoder. Encoding 2-pass MPEG-4 ("DivX") The name comes from the fact that this method encodes the file twice. The first encoding (dubbed pass) creates some temporary files (*.log) with a size of few megabytes, do not delete them yet (you can delete the AVI). In the second pass, the 2-pass output file is created, using the bitrate data from the temporary files. The resulting file will have much better image quality. If this is the first time you heard about this, you should consult some guides available on the net. copy audio track 2-pass encode of a DVD to an MPEG-4 ("DivX") AVI while copying the audio track. mencoder dvd://2 -ovc lavc -lavcopts vcodec=mpeg4:vpass=1 -oac copy -o movie.avi mencoder dvd://2 -ovc lavc -lavcopts vcodec=mpeg4:vpass=2 -oac copy -o movie.avi encode audio track 2-pass encode of a DVD to an MPEG-4 ("DivX") AVI while encoding the audio track to MP3. mencoder dvd://2 -ovc lavc -lavcopts vcodec=mpeg4:vpass=1 -oac mp3lame -lameopts vbr=3 -o movie.avi mencoder dvd://2 -ovc lavc -lavcopts vcodec=mpeg4:vpass=2 -oac mp3lame -lameopts vbr=3 -o movie.avi Encoding to MPEG format MEncoder can create MPEG (MPEG-PS) format output files. It's probably useful only with libavcodec's mpeg1video codec, because players - except MPlayer - expect MPEG-1 video, and MPEG-1 layer 2 (MP2) audio streams in MPEG files. This feature is not very useful right now, aside that it probably has many bugs, but the more importantly because MEncoder currently cannot encode MPEG-1 layer 2 (MP2) audio, which all other players expect in MPEG files. To change MEncoder's output file format, use the option. Example: mencoder -of mpeg -ovc lavc -lavcopts vcodec=mpeg1video -oac copy other_options media.avi -o output.mpg Rescaling movies Often the need to resize movie images' size emerges. Its reasons can be many: decreasing file size, network bandwidth,etc. Most people even do rescaling when converting DVDs or SVCDs to DivX AVI. If you wish to rescale, read the Preserving aspect ratio section. The scaling process is handled by the scale video filter: . Its quality can be set with the option. If it's not specified, MEncoder will use 0: fast bilinear. Usage: mencoder input.mpg -ovc lavc -lavcopts vcodec=mpeg4 -vf scale=640:480 -o output.avi Stream copying MEncoder can handle input streams in two ways: encode or copy them. This section is about copying. Video stream (option ): nice stuff can be done :) Like, putting (not converting!) FLI or VIVO or MPEG-1 video into an AVI file! Of course only MPlayer can play such files :) And it probably has no real life value at all. Rationally: video stream copying can be useful for example when only the audio stream has to be encoded (like, uncompressed PCM to MP3). Audio stream (option ): straightforward. It is possible to take an external audio file (MP3, WAV) and mux it into the output stream. Use the option for this. Fixing AVIs with broken index or interleaving Easiest thing. We simply copy the video and audio streams, and MEncoder generates the index. Of course this cannot fix possible bugs in the video and/or audio streams. It also fixes files with broken interleaving, thus the option won't be needed for them anymore. Command: mencoder -idx input.avi -ovc copy -oac copy -o output.avi Appending multiple AVI files As a side-effect, the broken AVI fixer function enables MEncoder to append 2 (or more) AVI files: Command: cat 1.avi 2.avi > 3.avi mencoder -noidx -ovc copy -oac copy -o output.avi 3.avi This expects 1.avi and 2.avi to use the same codecs, resolution, stream rate etc, and at least 1.avi must not be broken. You may need to fix your input AVI files first, as described above. Encoding with the <systemitem class="library">libavcodec</systemitem> codec family libavcodec provides simple encoding to a lot of interesting video and audio formats. You can encode to the following codecs (more or less up to date): Codec nameDescription mjpeg Motion JPEG ljpeg Lossless JPEG h263 H.263 h263p H.263+ mpeg4 ISO standard MPEG-4 (DivX 5, XVID compatible) msmpeg4 pre-standard MPEG-4 variant by MS, v3 (AKA DivX3) msmpeg4v2 pre-standard MPEG-4 by MS, v2 (used in old asf files) wmv1 Windows Media Video, version 1 (AKA WMV7) wmv2 Windows Media Video, version 2 (AKA WMV8) rv10 an old RealVideo codec mpeg1video MPEG-1 video mpeg2video MPEG-2 video huffyuv lossless compression asv1 ASUS Video v1 asv2 ASUS Video v2 ffv1 FFmpeg's lossless video codec The first column contains the codec names that should be passed after the vcodec config, like: An example, with MJPEG compression: mencoder dvd://2 -o title2.avi -ovc lavc -lavcopts vcodec=mjpeg -oac copy Encoding from multiple input image files (JPEG, PNG, TGA, SGI) MEncoder is capable of creating movies from one or more JPEG, PNG or TGA files. With simple framecopy it can create MJPEG (Motion JPEG), MPNG (Motion PNG) or MTGA (Motion TGA) files. Explanation of the process: MEncoder decodes the input image(s) with libjpeg (when decoding PNGs, it will use libpng). MEncoder then feeds the decoded image to the chosen video compressor (DivX4, XviD, FFmpeg msmpeg4, etc.). Examples The explanation of the option is in the man page. Creating an MPEG-4 file from all the JPEG files in the current directory: mencoder mf://*.jpg -mf w=800:h=600:fps=25:type=jpg -ovc lavc -lavcopts vcodec=mpeg4 -oac copy -o output.avi Creating an MPEG-4 file from some JPEG files in the current directory: mencoder mf://frame001.jpg,frame002.jpg -mf w=800:h=600:fps=25:type=jpg -ovc lavc -lavcopts vcodec=mpeg4 -oac copy -o output.avi Creating a Motion JPEG (MJPEG) file from all the JPEG files in the current directory: mencoder mf://*.jpg -mf w=800:h=600:fps=25:type=jpg -ovc copy -oac copy -o output.avi Creating an uncompressed file from all the PNG files in the current directory: mencoder mf:// -mf w=800:h=600:fps=25:type=png -ovc raw -oac copy -o output.avi Width must be integer multiple of 4, it's a limitation of the RAW RGB AVI format. Creating a Motion PNG (MPNG) file from all the PNG files in the current directory: mencoder mf://*.png -mf w=800:h=600:fps=25:type=png -ovc copy -oac copy -o output.avi Creating a Motion TGA (MTGA) file from all the TGA files in the current directory: mencoder mf://*.tga -mf w=800:h=600:fps=25:type=tga -ovc copy -oac copy -o output.avi Extracting DVD subtitles to VOBsub file MEncoder is capable of extracting subtitles from a DVD into VOBsub formatted files. They consist of a pair of files ending in .idx and .sub and are usually packaged in a single .rar archive. MPlayer can play these with the and options. You specify the basename (i.e without the .idx or .sub extension) of the output files with and the index for this subtitle in the resulting files with . If the input is not from a DVD you should use to indicate the .ifo file needed to construct the resulting .idx file. If the input is not from a DVD and you do not have the .ifo file you will need to use the option to let it know what language id to put in the .idx file. Each run will append the running subtitle if the .idx and .sub files already exist. So you should remove any before starting. Copying two subtitles from a DVD while doing 2-pass encoding rm subtitles.idx subtitles.sub mencoder dvd://1 -oac copy -ovc lavc -lavcopts vcodec=mpeg4:vpass=1 -vobsubout subtitles -vobsuboutindex 0 -sid 2 mencoder dvd://1 -oac copy -ovc lavc -lavcopts vcodec=mpeg4:vpass=2 -vobsubout subtitles -vobsuboutindex 1 -sid 5 Copying a french subtitle from an MPEG file rm subtitles.idx subtitles.sub mencoder movie.mpg -ifo movie.ifo -vobsubout subtitles -vobsuboutindex 0 -vobsuboutid fr -sid 1 Preserving aspect ratio DVDs and SVCDs (i.e. MPEG-1/2) files contain an aspect ratio value, which describes how the player should scale the video stream, so humans won't have egg heads (ex.: 480x480 + 4:3 = 640x480). However when encoding to AVI (DivX) files, you have be aware that AVI headers don't store this value. Rescaling the movie is disgusting and time consuming, there has to be a better way! There is MPEG-4 has an unique feature: the video stream can contain its needed aspect ratio. Yes, just like MPEG-1/2 (DVD, SVCD) and H.263 files. Regretfully, there are no video players outside which support this attribute of MPEG-4, except MPlayer. This feature can be used only with libavcodec's mpeg4 codec. Keep in mind: although MPlayer will correctly play the created file, other players will use the wrong aspect ratio. You seriously should crop the black bands over and below the movie image. See the man page for the usage of the cropdetect and crop filters. Usage mencoder sample-svcd.mpg -ovc lavc -lavcopts vcodec=mpeg4:autoaspect -vf crop=714:548:0:14 -oac copy -o output.avi Custom inter/intra matrices With this feature of libavcodec you are able to set custom inter (I-frames/keyframes) and intra (P-frames/predicted frames) matrices. It is supported by many of the codecs: mpeg1video and mpeg2video are reported as working. A typical usage of this feature is to set the matrices preferred by the KVCD specifications. The KVCD "Notch" Quantization Matrix: Intra: 8 9 12 22 26 27 29 34 9 10 14 26 27 29 34 37 12 14 18 27 29 34 37 38 22 26 27 31 36 37 38 40 26 27 29 36 39 38 40 48 27 29 34 37 38 40 48 58 29 34 37 38 40 48 58 69 34 37 38 40 48 58 69 79 Inter: 16 18 20 22 24 26 28 30 18 20 22 24 26 28 30 32 20 22 24 26 28 30 32 34 22 24 26 30 32 32 34 36 24 26 28 32 34 34 36 38 26 28 30 32 34 36 38 40 28 30 32 34 36 38 42 42 30 32 34 36 38 40 42 44 Usage: $ mencoder input.avi -o output.avi -oac copy -ovc lavc -lavcopts inter_matrix=...:intra_matrix=... $ mencoder input.avi -ovc lavc -lavcopts vcodec=mpeg2video:intra_matrix=8,9,12,22,26,27,29,34,9,10,14,26,27,29,34,37, 12,14,18,27,29,34,37,38,22,26,27,31,36,37,38,40,26,27,29,36,39,38,40,48,27, 29,34,37,38,40,48,58,29,34,37,38,40,48,58,69,34,37,38,40,48,58,69,79 :inter_matrix=16,18,20,22,24,26,28,30,18,20,22,24,26,28,30,32,20,22,24,26, 28,30,32,34,22,24,26,30,32,32,34,36,24,26,28,32,34,34,36,38,26,28,30,32,34, 36,38,40,28,30,32,34,36,38,42,42,30,32,34,36,38,40,42,44 -oac copy -o svcd.mpg Making a high quality MPEG-4 ("DivX") rip of a DVD movie One frequently asked question is "How do I make the highest quality DVD rip possible? I don't care about file size, I just want the best quality." This question is perhaps at least somewhat wrongly posed. After all, if you don't care about file size, why not simply copy the MPEG-2 video stream from the DVD whole? Sure, your AVI will end up being 5GB, give or take, but if you want the best quality and don't care about size, this is certainly your best option. In fact, the reason you want to transcode a DVD into MPEG-4 is specifically because you do care about file size. It's 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're likely to end up disappointed with your results. Below we'll investigate some of these issues, and then have a look at an example. We assume you're using libavcodec to encode the video, although the theory applies to other codecs as well. The main assumption of this guide is that you have no specific file size constraints and have no problem giving up bits in exchange for quality. While much of the information presented here is useful in any case, some of it may work against you if you have a file size goal, such as fitting a video on a CD. Constant Quantizer vs. 2-pass There are three approaches to encoding the video: constant bitrate (CBR), constant quantizer, and two-pass (ABR, or average bitrate). In each of these modes, libavcodec 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 libavcodec 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.) When you specify a constant bitrate, libavcodec 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 don't 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 libavcodec will use the lowest possible quantizer for each macroblock (as specified by , which is 2 by default). As soon as you specify a low enough bitrate that libavcodec is forced to use a higher quantizer, then you're almost certainly ruining the quality of your video. In general, you should avoid CBR altogether if you care about quality. With constant quantizer, libavcodec uses the same quantizer, as specified by the option, on every macroblock. If you want the highest quality rip possible, again ignoring bitrate, you can use . This will yield the same bitrate and PSNR (peak signal-to-noise ratio) as CBR with =infinity and the default of 2. 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's only so many bits on your hard disk. 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 low detail scenes, higher quantizers will likely be used, and during slow moving or high detail scenes, lower quantizers will be used. If you use , then you're wasting bits. If you use , then you're not getting the highest quality rip. Suppose you rip a DVD at , and the result is 1800Kbit. If you do a two-pass encode with , the resulting video will have higher quality for the same bitrate. Since you're now convinced that two-pass is the way to go, the real question now is what bitrate to use? The answer is that there's 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. 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's a good idea to experiment with scenes at different bitrates to get a feel. Cropping and Scaling Native DVD resolution is 720x480 for NTSC, and 720x576 for PAL, but there's an aspect flag that specifies whether it's 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. MPlayer provides a crop detection filter that will determine the crop rectangle (). Because MPEG-4 uses 16x16 macroblocks, you'll want to make sure that each dimension of the video you're encoding is a multiple of 16 or else you will be degrading quality, especially at lower bitrates. You can do this by rounding the width and height of the crop rectangle down to the nearest multiple of 16. When cropping, you'll want to increase the y-offset by half the difference of the old and the new height so that the resulting video is taken from the center of the frame. And because of the way DVD video is sampled, make sure the offset is an even number. (In fact, as a rule, never use odd values for any parameter when you're cropping and scaling video.) If you're not comfortable throwing a few extra pixels away, you might prefer instead to scale the video instead. We'll look at this in our example below. Also, be careful about "half black" pixels at the edges. Make sure you crop these out too, or else you'll be wasting bits there that are better spent elsewhere. After all is said and done, you'll probably end up with video whose pixels aren't quite 1.85:1 or 2.35:1, but rather something close to that. You could calculate the new aspect ratio manually, but MEncoder offers an option for libavcodec called that will do this for you. Absolutely do not scale this video in order to square the pixels unless you like to waste your hard disk space. Scaling should be done on playback, and the player will use the aspect stored in the AVI to determine the correct resolution. Audio Audio is a much simpler problem to solve: just leave it as is. Even AC3 5.1 streams are at most 448Kbit/s, and they're worth every bit. You might be tempted to transcode the audio to high quality Ogg Vorbis, but just because you don't have an A/V receiver for AC3 pass-through today doesn't mean you won't have one tomorrow. Future-proof your DVD rips by preserving the AC3 stream. Interlacing and Telecine Almost all movies are shot at 24 fps. Because NTSC is 29.97 fps, some processing must be done to this 24 fps video to make it run at the correct NTSC framerate. The process is called 3:2 pulldown, commonly referred to as telecine (because pulldown is often applied during the telecine process), and, naively described, it works by slowing the film down to 23.976 fps, and repeating every fourth frame. No special processing, however, is done to the video for PAL DVDs, which run at 25 fps. (Technically, PAL can be telecined, called 2:2 pulldown, but this doesn't become an issue in practice.) The 24 fps film is simply played back at 25 fps. The result is that the movie runs slightly faster, but unless you're an alien, you probably won't notice the difference. Most PAL DVDs have pitch-corrected audio, so when they're played back at 25 fps things will sound right, even though the audio track (and hence the whole movie) has a running time that's 4% less than NTSC DVDs. Because the video in a PAL DVD hasn't been altered, you needn't worry much about frame rate. The source is 25 fps, and your rip will be 25 fps. However, if you're ripping an NTSC DVD movie, you may need to apply inverse telecine. For movies shot at 24 fps, the video on the NTSC DVD is either telecined 29.97 fps, or else it is progressive 24 fps and intended to be telecined on-the-fly by a DVD player. On the other hand, TV series are usually only interlaced, not telecined. This is not a hard rule: some TV series are interlaced (such as Buffy the Vampire Slayer) whereas some are a mixture of progressive and interlaced (such as Angel, or 24). It's highly recommended that you read the section on How to deal with telecine and interlacing in NTSC DVDs to learn how to handle the different possibilities. However, if you're mostly just ripping movies, likely you're either dealing with 24 fps progressive or telecined video, in which case you can use the filter . Filtering In general, you want to do as little filtering as possible to the movie in order to remain close to the original DVD source. Cropping is often necessary (as described above), but do not scale the video. Although scaling down is sometimes preferred to using higher quantizers, we want to avoid both these things: remember that we decided from the start to trade bits for quality. Also, do not adjust gamma, contrast, brightness, etc. What looks good on your display may not look good on others. These adjustments should be done on playback only. One thing you might want to do, however, is pass the video through a very light denoise filter, such as . Again, it's a matter of putting those bits to better use: why waste them encoding noise when you can just add that noise back in during playback? Increasing the parameters for will further improve compressibility, but if you increase the values too much, you risk degrading the image visibily. The suggested values above () are quite conservative; you should feel free to experiment with higher values and observe the results for yourself. Example So, you've just bought your shiny new copy of Harry Potter and the Chamber of Secrets (widescreen edition, of course), and you want to rip this DVD so that you can add it to your Home Theatre PC. This is a region 1 DVD, so it's NTSC. The example below will still apply to PAL, except you'll omit (because the output framerate is the same as the input framerate), and of course the crop dimensions will be different. After running , we follow the process detailed in the section How to deal with telecine and interlacing in NTSC DVDs and discover that it's 24 fps progressive video, which means that we needn't use an inverse telecine filter, such as or . Next, we want to determine the appropriate crop rectangle, so we use the cropdetect filter: mplayer dvd://1 -vf cropdetect Make sure you seek to a fully filled frame (such as a bright scene), and you'll see in MPlayer's console output: crop area: X: 0..719 Y: 57..419 (-vf crop=720:362:0:58) We then play the movie back with this filter to test its correctness: mplayer dvd://1 -vf crop=720:362:0:58 And we see that it looks perfectly fine. Next, we ensure the width and height are a multiple of 16. The width is fine, however the height is not. Since we didn't fail 7th grade math, we know that the nearest multiple of 16 lower than 362 is 352. We could just use , but it'd be nice to take a little off the top and a little off the bottom so that we retain the center. We've shrunk the height by 10 pixels, but we don't want to increase the y-offset by 5-pixels since that's an odd number and will adversely affect quality. Instead, we'll increase the y-offset by 4 pixels: mplayer dvd://1 -vf crop=720:352:0:62 Another reason to shave pixels from both the top and the bottom is that we ensure we've eliminated any half-black pixels if they exist. Note that if your video is telecined, make sure the filter (or whichever inverse telecine filter you decide to use) appears in the filter chain before you crop. If it is interlaced, deinterlace before cropping. (If you choose to preserve the interlaced video, then make sure your vertical crop offset is a multiple of 4.) If you're really concerned about losing those 10 pixels, you might prefer instead to scale the dimensions down to the nearest multiple of 16. The filter chain would look like: -vf crop=720:362:0:58,scale=720:352 Scaling the video down like this will mean that some small amount of detail is lost, though it probably won't be perceptible. Scaling up will result in lower quality (unless you increase the bitrate). Cropping discards those pixels altogether. It's a tradeoff that you'll want to consider for each circumstance. For example, if the DVD video was made for television, you might want to avoid vertical scaling, since the line sampling corresponds to the way the content was originally recorded. On inspection, we see that our movie has a fair bit of action and high amounts of detail, so we pick 2400Kbit for our bitrate. We're now ready to do the 2-pass encode. Pass 1: mencoder dvd://1 -ofps 23.976 -oac copy -vf crop=720:352:0:62,hqdn3d=2:1:2 -ovc lavc \ -lavcopts vcodec=mpeg4:vbitrate=2400:v4mv:mbd=2:trell:cmp=3:subcmp=3:mbcmp=3:autoaspect:vpass=1 \ -o Harry_Potter_2.avi And pass 2 is the same, except that we specify : mencoder dvd://1 -ofps 23.976 -oac copy -vf crop=720:352:0:62,hqdn3d=2:1:2 -ovc lavc \ -lavcopts vcodec=mpeg4:vbitrate=2400:v4mv:mbd=2:trell:cmp=3:subcmp=3:mbcmp=3:autoaspect:vpass=2 \ -o Harry_Potter_2.avi The options will greatly increase the quality at the expense of encoding time. There's little reason to leave these options out when the primary goal is quality. The options select a comparison function that yields higher quality than the defaults. You might try experimenting with this parameter (refer to the man page for the possible values) as different functions can have a large impact on quality depending on the source material. For example, if you find libavcodec produces too much blocky artifacting, you could try selecting the experimental NSSE as comparison function via . For this movie, the resulting AVI will be 138 minutes long and nearly 3GB. And because you said that file size doesn't matter, this is a perfectly acceptable size. However, if you had wanted it smaller, you could try a lower bitrate. Increasing bitrates have diminishing returns, so while we might clearly see an improvement from 1800Kbit to 2000Kbit, it might not be so noticeable above 2000Kbit. Feel free to experiment until you're happy. Because we passed the source video through a denoise filter, you may want to add some of it back during playback. This, along with the post-processing filter, drastically improves the perception of quality and helps eliminate blocky artifacts in the video. With MPlayer's option, you can vary the amount of post-processing done by the spp filter depending on available CPU. Also, at this point, you may want to apply gamma and/or color correction to best suit your display. For example: mplayer Harry_Potter_2.avi -vf spp,noise=9ah:5ah,eq2=1.2 -autoq 3 How to deal with telecine and interlacing within NTSC DVDs Introduction I suggest you visit this page if you don't understand much of what is written in this document: http://www.divx.com/support/guides/guide.php?gid=10 This URL links to an understandable and reasonably comprehensive description of what telecine is. For technical reasons pertaining to the limitations of early television hardware, all video intended to be displayed on an NTSC television set must be 59.94 fields per second. Made-for-TV movies and shows are often filmed directly at 59.94 fields per second, but the majority of cinema is filmed at 24 or 23.976 frames per second. When cinematic movie DVDs are mastered, the video is then converted for television using a process called telecine. On a DVD, the video is never actually stored as 59.94 fields per second. For video that was originally 59.94, each pair of fields is combined to form a frame, resulting in 29.97 frames per second. Hardware DVD players then read a flag embedded in the video stream to determine whether the odd- or even-numbered lines should form the first field. Usually, 23.976 frames per second content stays as it is when encoded for a DVD, and the DVD player must perform telecining on-the-fly. Sometimes, however, the video is telecined before being stored on the DVD; even though it was originally 23.976 frames per second, it becomes 59.94 fields per second, and is stored on the disk as 29.97 frames per second. When looking at individual frames formed from 59.94 fields per second video, telecined or otherwise, interlacing is clearly visible wherever there is any motion, because one field (say, the even-numbered lines) represents a moment in time 1/59.94th of a second later than the other. Playing interlaced video on a computer looks ugly both because the monitor is higher resolution and because the video is shown frame-after-frame instead of field-after-field. Notes: This section only applies to NTSC DVDs, and not PAL. The example MEncoder lines throughout the document are not intended for actual use. They are simply the bare minimum required to encode the pertaining video category. How to make good DVD rips or fine-tune libavcodec for maximum quality is not within the scope of this document. There are a couple footnotes specific to this guide, linked like this: [1] How to tell what type of video you have Progressive Progressive video was originally filmed at 23.976 fps, and stored on the DVD without alteration. When you play a progressive DVD in MPlayer, MPlayer will print the following line as soon as the movie begins to play: demux_mpg: 24fps progressive NTSC content detected, switching framerate. From this point forward, demux_mpg should never say it finds "30fps NTSC content." When you watch progressive video, you should never see any interlacing. Beware, however, because sometimes there is a tiny bit of telecine mixed in, where you wouldn't expect. I've encountered TV show DVDs that have one second of telecine at every scene change, or at seemingly random places. I once watched a DVD that had a progressive first half, and the second half was telecined. If you want to be really thorough, you can scan the entire movie: mplayer dvd://1 -nosound -vo null -benchmark Using makes MPlayer play the movie as quickly as it possibly can; still, depending on your hardware, it can take a while. Every time demux_mpg reports a framerate change, the line immediately above will show you the time at which the change occurred. Sometimes progressive video is referred to as "soft-telecine" because it is intended to be telecined by the DVD player. Telecined Telecined video was originally filmed at 23.976, but was telecined before it was written to the DVD. MPlayer does not (ever) report any framerate changes when it plays telecined video. Watching a telecined video, you will see interlacing artifacts that seem to "blink": they repeatedly appear and disappear. You can look closely at this by mplayer dvd://1 -speed 0.1 Seek to a part with motion. Look at the pattern of interlaced-looking and progressive-looking frames. If the pattern you see is PPPII,PPPII,PPPII,... then the video is telecined. If you see some other pattern, then the video may have been telecined using some non-standard method and MEncoder cannot losslessly convert it to progressive. If you don't see any pattern at all, then it is most likely interlaced. Sometimes telecined video is referred to as "hard-telecine". Interlaced Interlaced video was originally filmed at 59.94 fields per second, and stored on the DVD as 29.97 frames per second. The interlacing is a result of combining pairs of fields into frames, because within each frame, each field is 1/59.94 seconds apart. As with telecined video, MPlayer should not ever report any framerate changes when playing interlaced content. When you view an interlaced video closely with , you will see that every single frame is interlaced. Mixed progressive and telecine All of a "mixed progressive and telecine" video was originally 23.976 frames per second, but some parts of it ended up being telecined. When MPlayer plays this category, it will (often repeatedly) switch back and forth between "30fps NTSC" and "24fps progressive NTSC". Watch the bottom of MPlayer's output to see these messages. You should check the "30fps NTSC" sections to make sure they are actually telecine, and not just interlaced. Mixed progressive and interlaced In "mixed progressive and interlaced" content, progressive and interlaced video have been spliced together. This category looks just like "mixed progressive and telecine", until you examine the 30fps sections and see that they don't have the telecine pattern. How to encode each category As I mentioned in the beginning, example MEncoder lines below are not meant to actually be used; they only demonstrate the minimum parameters to properly encode each category. Progressive Progressive video requires no special filtering to encode. The only parameter you need to be sure to use is . Otherwise, MEncoder will try to encode at 29.97 fps and duplicate frames. mencoder dvd://1 -nosound -ovc lavc -ofps 23.976 Telecined Telecine can be reversed to retrieve the original 23.976 content, using a process called inverse-telecine. MPlayer contains two filters to accomplish this: and . You can read the manual page to see their differences, but for DVDs I've never had a problem with . Note that you should always inverse-telecine before any rescaling; unless you really know what you're doing, inverse-telecine before cropping, too [1]. Again, is needed, too. mencoder dvd://1 -nosound -vf ivtc=1 -ovc lavc -ofps 23.976 Interlaced For most practical cases it is not possible to retrieve a complete progressive video from interlaced content. The only way to do so without losing half of the vertical resolution is to double the framerate and try to "guess" what ought to make up the corresponding lines for each field (this has drawbacks - see method 3). Encode the video in interlaced form. Normally, interlacing wreaks havoc with the encoder's ability to compress well, but libavcodec has two parameters specifically for dealing with storing interlaced video a bit better: and . Also, using is strongly recommended [2] because it will encode macroblocks as non-interlaced in places where there is no motion. Note that is NOT needed here. mencoder dvd://1 -nosound -ovc lavc -lavcopts ildct:ilme:mbd=2 Use a deinterlacing filter before encoding. There are several of these filters available to choose from, each with its own advantages and disadvantages. Consult to see what's available (grep for "deint"), and search the MPlayer mailing lists to find many discussions about the various filters. Again, the framerate is not changing, so no . Also, deinterlacing should be done after cropping [1] and before scaling. mencoder dvd://1 -nosound -vf pp=lb -ovc lavc Unfortunately, this option is buggy with MEncoder; it ought to work well with MEncoder G2, but that isn't here yet. You might experience crahes. Anyway, the purpose of is to create a full frame out of each field, which makes the framerate 59.94. The advantage of this approach is that no data is ever lost; however, since each frame comes from only one field, the missing lines have to be interpolated somehow. There are no very good methods of generating the missing data, and so the result will look a bit similar to when using some deinterlacing filters. Generating the missing lines creates other issues, as well, simply because the amount of data doubles. So, higher encoding bitrates are required to maintain quality, and more CPU power is used for both encoding and decoding. tfields has several different options for how to create the missing lines of each frame. If you use this method, then Reference the manual, and chose whichever option looks best for your material. Note that when using you have to specify both and to be twice the framerate of your original source. mencoder dvd://1 -nosound -vf tfields=2 -ovc lavc -fps 59.94 -ofps 59.94 If you plan on downscaling dramatically, you can excise and encode only one of the two fields. Of course, you'll lose half the vertical resolution, but if you plan on downscaling to at most 1/2 of the original, the loss won't matter much. The result will be a progressive 29.97 frames per second file. The procedure is to use , then crop [1] and scale appropriately. Remember that you'll have to adjust the scale to compensate for the vertical resolution being halved. mencoder dvd://1 -nosound -vf field=0 -ovc lavc Mixed progressive and telecine In order to turn mixed progressive and telecine video into entirely progressive video, the telecined parts have to be inverse-telecined. There are two filters that accomplish this natively, but a better solution most of the time is to use two filters in conjunction (read onward for more detail). Currently the most reliable method to deal with this type of video is to, rather than inverse-telecine the telecined parts, telecine the non-telecined parts and then inverse-telecine the whole video. Sound confusing? softpulldown is a filter that goes through a video and makes the entire file telecined. If we follow softpulldown with either or , the final result will be entirely progressive. Cropping and scaling should be done after the inverse-telecine operations, and is needed. mencoder dvd://1 -nosound -vf softpulldown,ivtc=1 -ovc lavc -ofps 23.976 is designed to inverse-telecine telecined material while leaving progressive data alone. Pullup doesn't really work well with the current MEncoder, though, and is really intended for use with MEncoder G2 (whenever it's ready). It works fine without , but is needed to prevent choppy output. With , it sometimes fails. The problems arise from MEncoder's behavior of dropping frames to maintain synchronization between the audio and video: it drops frames before sending them through the filter chain, rather than after. As a result, is sometimes deprived of the data it needs. If MEncoder drops too many frames in a row, it starves 's buffers and causes it to crash. Even if MEncoder only drops one frame, still doesn't get to see it, and will end up operating on an incorrect sequence of frames. Even though this doesn't cause a crash, won't be able to make correct decisions on how to reassemble progressive frames, and will either match fields together incorrectly or drop several fields to compensate. I haven't used myself, but here's what D Richard Felker III has to say:

It's OK, but IMO it tries to deinterlace rather than doing inverse telecine too often (much like settop DVD players & progressive TVs) which gives ugly flickering and other artefacts. If you're going to use it, you at least need to spend some time tuning the options and watching the output first to make sure it's not messing up.

Mixed progressive and interlaced There are two options for dealing with this category, each of which is a compromise. You should decide based on the duration/location of each type. Treat it as progressive. The interlaced parts will look interlaced, and some of the interlaced fields will have to be dropped, resulting in a bit of uneven jumpiness. You can use a postprocessing filter if you want to, but it may slightly degrade the progressive parts. This option should definitely not be used if you want to eventually display the video on an interlaced device (with a TV card, for example). If you have interlaced frames in a 23.976 frames per second video, they will be telecined along with the progressive frames. Half of the interlaced "frames" will be displayed for three fields' duration (3/59.94 seconds), resulting in a flicking "jump back in time" effect that looks quite bad. If you even attempt this, you must use a deinterlacing filter like or . It may also be a bad idea for progressive display, too. It will drop pairs of consecutive interlaced fields, resulting in a discontinuity that can be more visible than with the second method, which shows some progressive frames twice. 29.97 frames per second interlaced video is already a bit choppy because it really should be shown at 59.94 fields per second, so the duplicate frames don't stand out as much. Either way, it's best to consider your content and how you intend to display it. If your video is 90% progressive and you never intend to show it on a TV, you should favor a progressive approach. If it's only half progressive, you probably want to encode it as if it's all interlaced. Treat it as interlaced. Some frames of the progressive parts will need to be duplicated, resulting in uneven jumpiness. Again, deinterlacing filters may slightly degrade the progressive parts. Footnotes About cropping: Video data on DVDs are stored in a format called YUV 4:2:0. In YUV video, luma ("brightness") and chroma ("color") are stored separately. Because the human eye is somewhat less sensitive to color than it is to brightness, in a YUV 4:2:0 picture there is only one chroma pixel for every four luma pixels. In a progressive picture, each square of four luma pixels (two on each side) has one common chroma pixel. You must crop progressive YUV 4:2:0 to even resolutions, and use even offsets. For example, is OK but is not. When you are dealing with interlaced YUV 4:2:0, the situation is a bit more complicated. Instead of every four luma pixels in the frame sharing a chroma pixel, every four luma pixels in each field share a chroma pixel. When fields are interlaced to form a frame, each scanline is one pixel high. Now, instead of all four luma pixels being in a square, there are two pixels side-by-side, and the other two pixels are side-by-side two scanlines down. The two luma pixels in the intermediate scanline are from the other field, and so share a different chroma pixel with two luma pixels two scanlines away. All this confusion makes it necessary to have vertical crop dimensions and offsets be multiples of four. Horizontal can stay even. For telecined video, I recommend that cropping take place after inverse telecining. Once the video is progressive you only need to crop by even numbers. If you really want to gain the slight speedup that cropping first may offer, you must crop vertically by multiples of four or else the inverse-telecine filter won't have proper data. For interlaced (not telecined) video, you must always crop vertically by multiples of four unless you use before cropping. About encoding parameters and quality: Just because I recommend here doesn't mean it shouldn't be used elsewhere. Along with , is one of the two libavcodec options that increases quality the most, and you should always use at least those two unless the drop in encoding speed is prohibitive (e.g. realtime encoding). There are many other options to libavcodec that increase encoding quality (and decrease encoding speed) but that is beyond the scope of this document.