Often the need to resize movie images' size emerges. Its reasons can be many, examples are decreasing output file size, encoding SVCDs to DivX. Ripped DVDs are mostly rescaled, for example a 4:3 DVD should be 640x480, especially when you want it to fit to 1 CD, and have good quality at the same time. SVCDs have 480x480 size, and their header contains the aspect ratio the player should use (Ex.: 480x480 + 4:3 = 640x480). However when encoding to AVI (DivX) files, you have be aware that AVI headers don't store this value. Thus, the only solution is rescaling.

MEncoder can scale input images if they come in YV12 format (for example: ffdivx, odivx drivers, or mpeg1/2). The output size is specified with the -x, and -y options. Furthermore, there are some rescaling filters in MEncoder, see the manpage for them ! They can be specified with the -sws option. If not specified, MEncoder will use 0 : fast bilinear.

Rescaling is very simple :
    mencoder sample-svcd.mpg -divx4opts br=1300 -x 640 -y 480 -sws 2 -o output.avi

MEncoder can handle input streams in two ways : encode or copy them. This section is about copying.

• Video stream (option -ovc copy) : nice stuff can be done :)
  Like, putting (not converting!) FLI or VIVO or MPEG1 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 -oac copy) : straightforward. It is possible to take an external audio file (MP3, AC3, Vorbis) and mux it into the output stream. Use the -audiofile <filename> option for this.

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 -ni option won't be needed for them anymore.

Command : mencoder input.avi -ovc copy -oac copy -o output.avi

MEncoder is capable of creating movies from one or more JPEG or PNG files. With simple framecopy it can create MJPEG (Motion JPEG) or MPNG (Motion PNG) files.

Explanation of the process

MEncoder decodes the input image(s) with an available MJPEG video codec (when decoding PNGs, it will use libpng). By default it uses ffmjpeg, so you have to compile with libavcodec support (which is recommended anyways). Its disadvantage is that it can't handle some JPEG types (green image will be encoded for these). Use some external utility to convert those images into edible format.
You can freely choose any other MJPEG decoder, like mcmjpg32.dll (MainConcept Motion JPEG) if installed, and after checking codecs.conf and checking the videocodec line which refers to this file, you'll learn you have to use the -vc mjpeg option for it.

MEncoder then feeds the decoded image to the chosen video compressor (DivX4, Xvid, ffmpeg msmpeg4, etc...). Watch for the PNG decoder, as currently it can output only to RGB formats, thus can't be used with codecs that require YUV as input, like DivX4 or ffmpeg's msmpeg4.

Examples

  mencoder [options] [input file] [options] ...