HTML5: Up and Running by Pilgrim Mark

Author:Pilgrim, Mark [Mark Pilgrim]
Language: eng
Format: epub
Tags: COMPUTERS / Programming Languages / HTML
ISBN: 9781449399665
Publisher: O'Reilly Media, Inc.
Published: 2010-08-05T16:00:00+00:00

Instructions for Windows, which I have not personally tested.

The latest version of mkclean.

Ready? OK. On the command line, run ffmpeg with no parameters and verify that it was compiled with VP8 support:

you@localhost$ ffmpeg FFmpeg version SVN-r23197, Copyright (c) 2000-2010 the FFmpeg developers built on May 19 2010 22:32:20 with gcc 4.4.3 configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-pthreads --enable-libfaac --enable-libfaad --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libx264 --enable-libxvid --enable-x11grab --enable-libvpx-vp8

If you don’t see the magic words --enable-libvpx-vp8, you don’t have the right version of ffmpeg. (If you swear you just compiled it properly, check to see if you have two versions installed. That’s fine, they won’t conflict with each other—you’ll just need to use the full path of the VP8-enabled version of ffmpeg.)

I’m going to show you how to do a two-pass encode (see Encoding H.264 Video with HandBrake). The first pass just scans through the input video file (-i pr6.dv) and writes out some statistics to a logfile (which will be autonamed pr6.dv-0.log). You specify the video codec with the -vcodec parameter:

you@localhost$ ffmpeg -pass 1 -passlogfile pr6.dv -threads 16 -token_partitions 4 -altref 1 -lag 16 -keyint_min 0 -g 250 -mb_static_threshold 0 -skip_threshold 0 -qmin 1 -qmax 51 -i pr6.dv -vcodec libvpx_vp8 -an -f rawvideo -y NUL

Most of the ffmpeg command line has nothing to do with VP8 or WebM. libvp8 does support a number of VP8-specific options that you can pass to ffmpeg, but I don’t yet know how any of them work. Once I find a good explanation of these options, I’ll provide a link on this book’s website.

For the second pass, ffmpeg will read the statistics it wrote during the first pass and actually do the encoding of the video and the audio. It will write out an MKV file, which we will convert to a WebM file later. (Eventually ffmpeg will be able to write WebM files directly, but that functionality is currently broken in a subtle and pernicious way.) Here’s the command line for the second pass:

you@localhost$ ffmpeg -pass 2 -passlogfile pr6.dv -threads 16 -token_partitions 4 -altref 1 -lag 16 -keyint_min 0 -g 250 -mb_static_threshold 0 -skip_threshold 0 -qmin 1 -qmax 51 -i pr6.dv -vcodec libvpx_vp8 -b 614400 -s 320x240 -aspect 4:3 -acodec vorbis -y pr6.mkv

There are five important parameters here:

-vcodec libvpx_vp8

Specifies that we’re encoding with the VP8 video codec. WebM always uses VP8 video.

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