yuvscaler(1)

💖 yuvscaler(1) — the MJPEG tools manual, but make it make sense 💖

okay bestie, so this is the page for yuvscaler, part of the MJPEG tools manual, and honestly? she's a main character. Let's get into it. 🦋

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✨ NAME ✨

yuvscaler — UPscales or DOWNscales a YUV4MPEG2 stream to a specified format

so basically she takes your stream and resizes it. up. down. whatever you need. iconic behavior honestly. 💅

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🌸 SYNOPSIS 🌸

yuvscaler [-I input_keyword] [-M mode_keyword] [-O output_keyword]
[-n p|s|n] [-v 0-2] [-h]

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🎀 DESCRIPTION 🎀

yuvscaler is a general (UP or DOWN) scaling utility that is provided to allow conversion between different video formats. she reads in a YUV4MPEG2 format stream from stdin (like, the kind of thing lav2yuv hands you) and outputs that same kind of stream to stdout — so like, for example, something else can eat it, like mpeg2enc. 🍓

ngl the most common glow-up people use yuvscaler for is making input that's suitable for MPEG encoding to VCD or SVCD formats using mpeg2enc(1). that's the whole vibe.

and she's smart about it, fr fr — yuvscaler will automatically take into account PAL/SECAM and NTSC format, plus widescreen (16:9) format and interlacing. Use of yuvscaler was designed to be straightforward. no cap. 🫶

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🔥 EXAMPLES 🔥

VCD encoding:

lav2yuv my-file.avi | yuvscaler -O VCD | mpeg2enc -f 1 -o vcd.%d.m1v

SVCD encoding:

lav2yuv my-file.qt | yuvscaler -O SVCD | mpeg2enc -f 4 -o svcd.%d.m2v

Encoding anamorphic 16:9 as letterboxed VCD:

lav2yuv my-ana16-9.eli | yuvscaler -M WIDE2VCD | mpeg2enc -f 1 -o
letterbox_vcd.%d.m1v

Encoding anamorphic 16:9 as letterboxed SVCD:

lav2yuv my-ana16-9.eli | yuvscaler -M WIDE2STD -O SVCD | mpeg2enc -f 4
-o letterbox_svcd.%d.m2v

Encoding anamorphic 16:9 as letterboxed DVD:

lav2yuv my-ana16-9.eli | yuvscaler -M WIDE2STD -O DVD | mpeg2enc -f 8 -o
letterbox_dvd.%d.m2v

literally pipe it in, pipe it out, slay. ✨

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👑 OPTIONS 👑

• -I input_keyword — specifies input processing options. Input options may be combined by using multiple -I flags. Possible input_keywords are:
  • USE_WidthxHeight+WidthOffset+HeightOffset — to select a useful area of the input frame (all multiple of 2, Height and HeightOffset multiple of 4 if interlaced), the rest of the image being discarded. like, bye to the extra bits. 💀
  • ACTIVE_WidthxHeight+WidthOffset+HeightOffset — to select an active area of the input frame (all multiple of 2, Height and HeightOffset multiple of 4 if interlaced), the rest of the image being made black. not discarded — just dressed in black. 🖤
• -M mode_keyword — sets the scaling mode options. Scaling mode options can be combined by giving several -M flags. Possible are:
  • BICUBIC — to use the (Mitchell-Netravalli) high-quality bicubic upsacling and/or downscaling algorithm. fancy algorithm, fancy results. 💅
  • RESAMPLE — to use a classical resampling algorithm -only for downscaling- that goes much faster than bicubic. For coherence reason, yuvscaler will use RESAMPLE if only downscaling is necessary, BICUBIC if not. she picks for you, that's the service. 🫶
  • WIDE2STD — convert widescreen anamorphic (16:9) input video into letterboxed (4:3), generating necessary black lines. Note that for MPEG applications if your player can properly decode anamorphic video you may wish to leave the video unscaled and simply specify the approprate format during MPEG encoding (see mpeg2enc(1)).
  • RATIO_WidthIn_WidthOut_HeightIn_HeightOut — to specified scaling ratios of WidthIn/WidthOut for width and HeightIN/HeightOut for height to be applied to the useful area. The output frames that result from scaling can have a different format than the output format specified using -O options(s). In this case, yuvscaler automatically generate necessary black lines and columns and/or skips necessary lines and columns to center the scaled image in the output frame.
  • WIDE2VCD — to scale anamorphic widescreen (16:9) frames into letterboxed VCD format (equivalent to -M WIDE2STD -O VCD).
  • FASTVCD — to transcode full sized frames to VCD (equivalent to -M RATIO_2_1_2_1 -O VCD, see below).
  • FAST_WIDE2VCD — to transcode full-sized anamorphic (16:9) frames to letter-boxed VCD (equivalent to -M WIDE2STD -M RATIO_2_1_2_1 -O VCD, see below).
  • NO_HEADER — to suppress stream header generation on output.
  • MMX — to use MMX functions for BICUBIC scaling (experimental feature!!). ⚠️ experimental, bestie, you've been warned.
• -O output_keyword — sets the output frame format options. Output format options can be combined by giving several -O flags. By default, output frames size will be the same as input frame sizes, as well as output frames interlacing if coherent with output keyword specification which prevails, top_first if not.
  • MONOCHROME — to generate monochrome frames on output. Chrominance information for the scaled pixels is set neutral (white). MPEG encoding of black and white video will be both inefficient and show annonying chrominance artifacts unless this is done. so like, do it. 🙈
  • VCD — to generate VCD compliant frames on output (taking care of PAL and NTSC standards). Non-interlaced output.
  • SVCD — to generate SVCD compliant frames on output (taking care of PAL and NTSC standards). Top-field-first interlaced frames.
  • DVD — to generate DVD compliant frames on output (taking care of PAL and NTSC standards). Top-field-first interlaced frames.
  • SIZE_WidthxHeight — to generate frames of size WidthxHeight on output (multiple of 4).

If VCD, SVCD or DVD keywords are not used, output interlacing is taken of the same type as input. By default, output frames size will be the same as input frame size.

• -n p|s|n — (usually not necessary) if norm could not be determined from data flux, specifies the OUTPUT norm for VCD/SVCD (p=pal,s=secam,n=ntsc).
• -v 0|1|2 — Specifies the degree of verbosity: 0=quiet, 1=normal, 2=verbose/debug.
• -h — Prints a summary of command line syntax.

Note: The most useful downscaling ratios are handled using dedicated optimised scaling routines. They are:

• RATIO_WidthIn_WidthOut_2_1 => Full-sized frame to VCD downscaling
• RATIO_3_2_1_1 => Full-sized frame to SVCD downscaling
• RATIO_1_1_4_3 => WIDE2STD downscaling mode
• RATIO_WidthIn_WidthOut_1_1 => downscaling only concerns width, not height
• RATIO_1_1_HeightIn_HeightOut => downscaling only concerns height, not width
• RATIO_2_1_2_1 => FASTVCD, slightly width distorted (real ratio 45 to 22) but faster full-sized frame to VCD downscaling (-M RATIO_2_1_2_1 -O VCD)
• RATIO_WidthIn_WidthOut_8_3 => specific to WIDE2VCD downscaling (-M WIDE2STD -O VCD)
• RATIO_2_1_8_3 => specific to (slighly distorted) FAST_WIDE2VCD downscaling (-M WIDE2STD -M RATIO_2_1_2_1 -O VCD)
• RATIO_1_1_1_1 => copy useful input part of possible several files into output frames

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💜 AUTHOR 💜

This man page was written by Xavier Biquard et al. 🫶

If you have questions, remarks, problems or you just want to contact the developers, the main mailing list for the MJPEG-tools is:

mjpeg-users@lists.sourceforge.net

For more info, see our website at

http://mjpeg.sourceforge.net/

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🌈 SEE ALSO 🌈

mjpegtools(1), lavpipe(1), lav2yuv(1) mpeg2enc(1)

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and that's the whole page bestie, we ate and left no crumbs. 💅✨ MJPEG Tools Team wrote this one, dated 26 Septembre 2001, for yuvscaler(1) — the version vibes are immaculate, the date is giving retro, and you're officially informed. mwah. 🎀🦋