Posts Tagged ffmpeg

Audio and Video improvements

April 14, 2009 at 4:18 pm · Filed under audio, movies ·Tagged , , , ,

Hi Patrons,

Yesterday we made live a large update to the way we create the audio and video displayed on our site.  Most folks might not notice the changes, so here’s a rundown:

For Audio:

  • We can now read and make mp3s from 24-bit Flac files.  This has been requested for many years and we are thrilled to get it working.
  • The Ogg audio files that we create from audio files will now be using an updated “libvorbis” library.  (The library we were using before today was from 2001! 8-) )
  • We are no longer making 64kb MP3s (or zips or m3u playlists of those files).  This was a judgement call — given how poor the sound quality is for these files and the fact that most people are getting more and more bandwidth to their devices and computers.
  • Simplified back-end system, relying more and more on “ffmpeg” for format conversion.
  • We will now (try to) make derivatives from “.aac” (Advanced Audio Coding) files and “.ra”/”.rm” (Real Audio) files.
  • General ability to read more kinds of audio files more reliably.

For Movies:

  • The Ogg Video files that we create from movies files will now be using an updated “libvorbis” library for their audio.  (Previously we were using the “non reference” library ogg encoder.  Now we are using the much asked for and newer “libvorbis” library).
  • Updated ffmpeg to v0.5.   This allows for a much wider range of source audio/video containers and codecs.  We will be able to derive HD-quality video formats like DV-50 and DV-100.   (For those interested in ffmpeg, changelog).
  • Better detection of widescreen movies (so less of our movies on our site will incorrectly appear “squooshed”).
  • General ability to read more kinds of video files more reliably.
  • Noting the prior point, we were able to get streaming videos for about 170 TV archive items that we could not process previously.

Enjoy!

–Tracey Jaquith

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Fast and reliable way to encode Theora Ogg videos using ffmpeg, libtheora, and liboggz

November 25, 2008 at 3:31 pm · Filed under movies ·Tagged , , , , ,


archive.org has started to make theora derivatives for movie files, where we create an Ogg Theora video format output for each movie file. after trying a bunch of tools over a good corpus of wide-ranging videos, i found a neat way to make the Archive derivatives.

High Level:

  • use ffmpeg to turn any video to “rawvideo”.
  • pipe its output to *another* ffmpeg to turn the video to “yuv4mpegpipe”.
  • pipe its output to the libtheora tool.
  • for videos with audio, ffmpeg create a vorbis audio .ogg file.
  • add tasty metadata (with liboggz utils).
  • combine the video and audio ogg files to an .ogv output!

Detailed example:

  • ffmpeg -an -deinterlace -s 400×300 -r 20.00 -i CapeCodMarsh.avi -vcodec rawvideo -pix_fmt yuv420p -f rawvideo – |  ffmpeg -an -f rawvideo -s 400×300 -r 20.00 -i – -f yuv4mpegpipe – |  libtheora-1.0/lt-encoder_example –video-rate-target 512k – -o tmp.ogv
  • ffmpeg -y -i CapeCodMarsh.avi -vn -acodec libvorbis -ac 2 -ab 128k -ar 44100 audio.ogg
  • oggz-comment audio.ogg -o audio2.ogg TITLE=”Cape Cod Marsh” ARTIST=”Tracey Jaquith” LICENSE=”http://creativecommons.org/licenses/publicdomain/” DATE=”2004″ ORGANIZATION=”Dumb Bunny Productions” LOCATION=http://www.archive.org/details/CapeCodMarsh
  • oggzmerge tmp.ogv audio2.ogg -o CapeCodMarsh.ogv

WTFs:

  • Why the double pipe above? Some videos could not go directly to yuv4mpegpipe format such that libtheora (or ffmpeg2theora) would work all the time.
  • We do the vorbis audio outside of libtheora (or ffmpeg2theora) to avoid any issues with Audio/Video sync.
  • We convert to yuv420p in the rawvideo step because ffmpeg2theora has (i think) some known issues of not handling all yuv422 video inputs (i found at least a few videos that did this).
  • We add the metadata to the audio vorbis ogg because adding it to the video ogv file wound up making the first video frame not a keyframe (!)

So this will end up working in Firefox 3.1 and greater — the new HTML “video” tag:

<video controls=”true” autoplay=”true” src=”http://www.archive.org/download/commute/commute.ogv”> for firefox betans </video>

This technique above worked nicely across a wide range of source and “trashy” 46 videos that I use for QA before making live a new way to derive our videos at archive.org.

-tracey jaquith

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