Simple yet powerful wrapper around the ffmpeg command for reading metadata and transcoding movies.
(sudo) gem install streamio-ffmpeg
This version is tested against ffmpeg 0.8. So no guarantees with earlier (or much later) versions. Output and input standards have inconveniently changed rather a lot between versions of ffmpeg. My goal is to keep this library in sync with new versions of ffmpeg as they come along.
require 'rubygems' require 'streamio-ffmpeg'
movie = FFMPEG::Movie.new("path/to/movie.mov") movie.duration # 7.5 (duration of the movie in seconds) movie.bitrate # 481 (bitrate in kb/s) movie.size # 455546 (filesize in bytes) movie.video_stream # "h264, yuv420p, 640x480 [PAR 1:1 DAR 4:3], 371 kb/s, 16.75 fps, 15 tbr, 600 tbn, 1200 tbc" (raw video stream info) movie.video_codec # "h264" movie.colorspace # "yuv420p" movie.resolution # "640x480" movie.width # 640 (width of the movie in pixels) movie.height # 480 (height of the movie in pixels) movie.frame_rate # 16.72 (frames per second) movie.audio_stream # "aac, 44100 Hz, stereo, s16, 75 kb/s" (raw audio stream info) movie.audio_codec # "aac" movie.audio_sample_rate # 44100 movie.audio_channels # 2 movie.valid? # true (would be false if ffmpeg fails to read the movie)
First argument is the output file path.
movie.transcode("tmp/movie.mp4") # Default ffmpeg settings for mp4 format
Keep track of progress with an optional block.
movie.transcode(movie.mp4") { |progress| puts progress } # 0.2 ... 0.5 ... 1.0
Give custom command line options with a string.
movie.transcode("movie.mp4", "-ac aac -vc libx264 -ac 2 ...")
Use the EncodingOptions parser for humanly readable transcoding options. Below you’ll find most of the supported options. Note that the :custom key will be used as is without modification so use it for any tricky business you might need.
options = {:video_codec => "libx264", :frame_rate => 10, :resolution => "320x240", :video_bitrate => 300, :video_bitrate_tolerance => 100, :croptop => 60, :cropbottom => 60, :cropleft => 10, :cropright => 10, :aspect => 1.333333, :audio_codec => "libfaac", :audio_bitrate => 32, :audio_sample_rate => 22050, :audio_channels => 1, :threads => 2, :custom => "-flags +loop -cmp +chroma -partitions +parti4x4+partp8x8 -flags2 +mixed_refs -me_method umh -subq 6 -refs 6 -rc_eq 'blurCplx^(1-qComp)' -coder 0 -me_range 16 -g 250 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -qcomp 0.6 -qmin 10 -qmax 51 -qdiff 4 -level 21"} movie.transcode("movie.mp4", options)
The transcode function returns a Movie object for the encoded file.
transcoded_movie = movie.transcode("tmp/movie.flv") transcoded_movie.video_codec # "flv" transcoded_movie.audio_codec # "mp3"
Aspect ratio is added to encoding options automatically if none is specified.
options = {:resolution => 320x180} # Will add -aspect 1.77777777777778 to ffmpeg
Preserve aspect ratio on width or height by using the preserve_aspect_ratio transcoder option.
widescreen_movie = FFMPEG::Movie.new("path/to/widescreen_movie.mov")
options = {:resolution => 320x240}
transcoder_options = {:preserve_aspect_ratio => :width}
widescreen_movie.transcode("movie.mp4", options, transcoder_options) # Output resolution will be 320x180
transcoder_options = {:preserve_aspect_ratio => :height}
widescreen_movie.transcode("movie.mp4", options, transcoder_options) # Output resolution will be 426x240
For constant bitrate encoding use video_min_bitrate and video_max_bitrate with buffer_size.
options = {:video_min_bitrate => 600, :video_max_bitrate => 600, :buffer_size => 2000} movie.transcode("movie.flv", options)
Use ffpreset files to avoid headaches when encoding with libx264 (www.ffmpeg.org/ffmpeg-doc.html#SEC13).
options = {:video_codec => "libx264", :video_preset => "medium"} # audio_preset and file_preset also availible movie.transcode("movie.mp4", options) # encodes video using libx264-medium.ffpreset
Copyright © 2010 Streamio Networks AB. See LICENSE for details.