avconvの使い方

$avconv <options for input> -i input <options for output> output

avconv ... -vf crop=w:h:x:y ...

$avconv ... -vf "crop=800:450:0:200, scale=w1280:h=720" ...

$ avconv -filters
avconv version 12.2, Copyright (c) 2000-2017 the Libav developers
  built on Oct 21 2017 23:09:27 with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.5) 20160609
Filters:
aformat          Convert the input audio to one of the specified formats.
amix             Audio mixing.
anull            Pass the source unchanged to the output.
asetpts          Set PTS for the output audio frame.
asettb           Set timebase for the audio output link.
ashowinfo        Show textual information for each audio frame.
asplit           Pass on the audio input to N audio outputs.
asyncts          Sync audio data to timestamps
atrim            Pick one continuous section from the input, drop the rest.
channelmap       Remap audio channels.
channelsplit     Split audio into per-channel streams
compand          Compress or expand audio dynamic range.
join             Join multiple audio streams into multi-channel output
resample         Audio resampling and conversion.
volume           Change input volume.
anullsrc         Null audio source, never return audio frames.
anullsink        Do absolutely nothing with the input audio.
blackframe       Detect frames that are (almost) black.
boxblur          Blur the input.
copy             Copy the input video unchanged to the output.
crop             Crop the input video to width:height:x:y.
cropdetect       Auto-detect crop size.
delogo           Remove logo from input video.
drawbox          Draw a colored box on the input video.
fade             Fade in/out input video
fieldorder       Set the field order.
format           Convert the input video to one of the specified pixel formats.
fps              Force constant framerate
framepack        Generate a frame packed stereoscopic video.
gradfun          Debands video quickly using gradients.
hflip            Horizontally flip the input video.
hqdn3d           Apply a High Quality 3D Denoiser.
hwdownload       Download a hardware frame to a normal frame
hwupload         Upload a normal frame to a hardware frame
interlace        Convert progressive video into interlaced.
lut              Compute and apply a lookup table to the RGB/YUV input video.
lutrgb           Compute and apply a lookup table to the RGB input video.
lutyuv           Compute and apply a lookup table to the YUV input video.
negate           Negate input video.
noformat         Force libavfilter not to use any of the specified pixel formats for the input to the next filter.
null             Pass the source unchanged to the output.
overlay          Overlay a video source on top of the input.
pad              Pad input image to width:height[:x:y[:color]] (default x and y: 0, default color: black).
pixdesctest      Test pixel format definitions.
scale            Scale the input video to width:height size and/or convert the image format.
select           Select frames to pass in output.
setdar           Set the frame display aspect ratio.
setpts           Set PTS for the output video frame.
setsar           Set the pixel sample aspect ratio.
settb            Set timebase for the video output link.
showinfo         Show textual information for each video frame.
shuffleplanes    Shuffle video planes
split            Pass on the input to N video outputs.
transpose        Transpose input video.
trim             Pick one continuous section from the input, drop the rest.
unsharp          Sharpen or blur the input video.
vflip            Flip the input video vertically.
yadif            Deinterlace the input image
color            Provide an uniformly colored input, syntax is: [color[:size[:rate]]]
movie            Read from a movie source.
nullsrc          Null video source, never return images.
rgbtestsrc       Generate RGB test pattern.
testsrc          Generate test pattern.
nullsink         Do absolutely nothing with the input video.
abuffer          Buffer audio frames, and make them accessible to the filterchain.
buffer           Buffer video frames, and make them accessible to the filterchain.
abuffersink      Buffer audio frames, and make them available to the end of the filter graph.
buffersink       Buffer video frames, and make them available to the end of the filter graph.
afifo            Buffer input frames and send them when they are requested.
fifo             Buffer input images and send them when they are requested.

$ avconv --help
avconv version 12.2, Copyright (c) 2000-2017 the Libav developers
  built on Oct 21 2017 23:09:27 with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.5) 20160609
Hyper fast Audio and Video encoder
usage: avconv [options] [[infile options] -i infile]... {[outfile options] outfile}...

Getting help:
    -h      -- print basic options
    -h long -- print more options
    -h full -- print all options (including all format and codec specific options, very long)
    -h type=name -- print all options for the named decoder/encoder/demuxer/muxer/filter
    See man avconv for detailed description of the options.

Print help / information / capabilities:
-L                  show license
-h topic            show help
-? topic            show help
-help topic         show help
--help topic        show help
-version            show version
-formats            show available formats
-codecs             show available codecs
-decoders           show available decoders
-encoders           show available encoders
-bsfs               show available bit stream filters
-protocols          show available protocols
-filters            show available filters
-pix_fmts           show available pixel formats
-sample_fmts        show available audio sample formats
-hwaccels           show available HW acceleration methods

Global options (affect whole program instead of just one file:
-loglevel loglevel  set libav* logging level
-v loglevel         set libav* logging level
-y                  overwrite output files
-n                  never overwrite output files
-stats              print progress report during encoding
-vol volume         change audio volume (256=normal)

Per-file main options:
-f fmt              force format
-c codec            codec name
-codec codec        codec name
-pre preset         preset name
-map_metadata outfile[,metadata]:infile[,metadata]  set metadata information of outfile from infile
-t duration         record or transcode "duration" seconds of audio/video
-fs limit_size      set the limit file size in bytes
-ss time_off        set the start time offset
-metadata string=string  add metadata
-target type        specify target file type ("vcd", "svcd", "dvd", "dv", "dv50", "pal-vcd", "ntsc-svcd", ...)
-frames number      set the number of frames to record
-filter filter_list  set stream filterchain
-filter_script filename  read stream filtergraph description from a file

Video options:
-vframes number     set the number of video frames to record
-r rate             set frame rate (Hz value, fraction or abbreviation)
-s size             set frame size (WxH or abbreviation)
-aspect aspect      set aspect ratio (4:3, 16:9 or 1.3333, 1.7777)
-vn                 disable video
-vcodec codec       force video codec ('copy' to copy stream)
-pass n             select the pass number (1 or 2)
-vf filter list     video filters

Audio options:
-aframes number     set the number of audio frames to record
-aq quality         set audio quality (codec-specific)
-ar rate            set audio sampling rate (in Hz)
-ac channels        set number of audio channels
-an                 disable audio
-acodec codec       force audio codec ('copy' to copy stream)
-vol volume         change audio volume (256=normal)
-af filter list     audio filters

Subtitle options:
-sn                 disable subtitle
-scodec codec       force subtitle codec ('copy' to copy stream)
-stag fourcc/tag    force subtitle tag/fourcc