Interlaced

Index: DOCS/xml/en/mencoder.xml =================================================================== RCS file: /cvsroot/mplayer/main/DOCS/xml/en/mencoder.xml,v retrieving revision 1.36 diff -u -r1.36 mencoder.xml --- DOCS/xml/en/mencoder.xml 7 Jan 2005 22:38:11 -0000 1.36 +++ DOCS/xml/en/mencoder.xml 19 Feb 2005 05:22:08 -0000 @@ -1036,7 +1036,7 @@ 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 + 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 @@ -1054,8 +1054,9 @@ - Sometimes progressive video is referred to as "soft-telecine" - because it is intended to be telecined by the DVD player. + Sometimes progressive video on DVDs is referred to as + "soft-telecine" because it is intended to be telecined by + the DVD player. @@ -1077,36 +1078,41 @@ You can look closely at this by - mplayer dvd://1 -speed 0.1 + mplayer dvd://1 Seek to a part with motion. + Use the "." key to step forward one frame at a time. + + 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. + may have been telecined using some non-standard method; + MEncoder cannot losslessly convert + non-standard telecine 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". + Sometimes telecined video on DVDs is referred to as + "hard-telecine". Since hard-telecine is already 59.94 fields + per second, the DVD player plays the video without any manipulation. 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. + and stored on the DVD as 29.97 frames per second. The interlacing effect + (often called "combing") is a result of combining pairs of + fields into frames. Each field is supposed to be 1/59.94 seconds apart, + and when they are displayed simultaneously the difference is apparent. @@ -1115,8 +1121,8 @@ - When you view an interlaced video closely with , - you will see that every single frame is interlaced. + When you view an interlaced video closely by frame-stepping with the + "." key, you will see that every single frame is interlaced. @@ -1176,6 +1182,15 @@ mencoder dvd://1 -nosound -ovc lavc -ofps 23.976 + + + It is often the case, however, that a video that looks progressive + actually has very short parts of telecine mixed in. Unless you are sure, + it is safest to treat the video as + mixed progressive and + telecine. The performance loss is small + [3]. + @@ -1183,20 +1198,10 @@ 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 + MPlayer contains several filters to + accomplish this; the best filter, , is described + in the mixed + progressive and telecine section. @@ -1266,7 +1271,7 @@ 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 + If you plan on downscaling dramatically, you can extract 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 @@ -1285,59 +1290,45 @@ 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). + inverse-telecined. There are three ways to accomplish this, + described below. Note that you should + always inverse-telecine before any + rescaling; unless you really know what you're doing, + inverse-telecine before cropping, too + [1]. + is needed here because the output video + will be 23.976 frames per second. - Currently the most reliable method to deal with this type of video + is designed to inverse-telecine + telecined material while leaving progressive data alone. In order to + work properly, must + be followed by the filter or + else MEncoder will crash. is, however, the cleanest and most accurate method + available for encoding both telecine and "mixed progressive and + telecine". + + mencoder dvd://1 -nosound -vf pullup,softskip -ovc lavc -ofps 23.976 + + + + + + An older method 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. + progressive. 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 @@ -1478,6 +1469,21 @@ + + About the performance of pullup: + + It is safe to use (along with ) on progressive video, and is usually a good idea unless + the source has been definitively verified to be entirely progressive. + The performace loss is small for most cases. On a bare-minimum encode, + causes MEncoder to + be 50% slower. Adding sound processing and advanced overshadows that difference, bringing the performance of + decrease of using down to 2%. + + + +