VP9 inside Ogg

Mapping of WebM codec inside Ogg container has been specified since the introduction of the WebM ^archived that refer to a document describing "Ogg container format mapping for WebM", and implementations of VP8 inside Ogg is already implemented by ffmpeg, development version of liboogz and some other softwares.

Some time later google release VP9, but no software that support VP9 inside Ogg yet. Firefox documentation claim that ^archived they can play VP8 and VP9 inside Ogg. Contrary to their documentation though, Firefox in fact can not play Ogg with VP8 codec (tested on Firefox version 104.0.1). On related note, Google Chrome and MS Edge do support VP8 inside Ogg. I can not test whether they can play VP9 inside Ogg because I can not even able to find any software that can put VP9 inside Ogg.

Because lack of OggVP9 implementation, for learning purpose, I am interested to implement it.

1. OggVP9 Mapping

Here is what I found while searching for the elusive document describing "Ogg container format mapping for WebM"

• The mapping document on the aftermentioned article ^archived is now inaccessible
• The Xiph Wiki also have no mention of it, which is understandable since they are not Xiph codecs
• A bit searching I found this PDF document which I believe is the same document linked on the article

From there I am implementing OggVP9 mostly using the same mapping as OggVP8 with VP9 specific changes

• The ID field is (obviously) set to VP90
• VP9 pts always increasing regardless visible or invisible frame, this also true for VP9 inside IVF format

More detail is written in this document.

However it should be noted that it is not offical OggVP9 mapping or anything. What I am doing is just taking existing OggVP8 specification, experimenting what is work for VP9 and documenting it.

2. Building code

My implementation is just a small patch for FFmpeg. All patches licensed under LGPL v2.1 or later, or the same license as FFmpeg this patch applied to. However the code is experimental and might contains serious bugs. Use it at your own risk.

2.1. Dependencies

To build from source you should install at least gcc, yasm, and development version of these libraries

• libvpx
• libopus
• libvorbis
• libtheora
• sdl2

2.2. Patch FFmpeg

This patch should work on FFmpeg 5.1, and may also work with more recent version of FFmpeg.

$ git clone https://github.com/aranugra/ogg-vp9.git
$ wget http://ffmpeg.org/releases/ffmpeg-5.1.tar.xz
$ tar -xf ffmpeg-5.1.tar.xz
$ patch -p1 -d ffmpeg-5.1 < ogg-vp9/ffmpeg/vp9-inside-ogg.patch

2.3. Configure, build and install

Configure and build FFmpeg

$ OGGVP9_PREFIX=/opt/ffmpeg-5.1-ogg-vp9
$ cd ffmpeg-5.1
$ ./configure --prefix=$OGGVP9_PREFIX --enable-libvpx --enable-libopus --enable-libtheora --enable-libvorbis --enable-shared
$ make -j3
$ make install

Then add $OGGVP9_PREFIX/bin to path if necessary.

2.4. Binary Packages

Compiled packages for Win64 are available on the release page.

3. Encoding & Playing OggVP9

3.1. Encoding

Encoding with constant rate factor

$ ffmpeg -i input.mp4 -f ogg -c:v libvpx-vp9 -crf 30 -b:v 0 -c:a libopus -b:a 160k output.ogv

Generally you can refer to VP9 encoding guide and just replace -f webm to -f ogg and replace output extension to .ogv.

3.2. Sample files

Here is some OggVP9 video samples.

3.3. Playing

To play OggVP9 video, you can use ffplay

$ ffplay output.ogv

For a real video player, you can build mpv linked against this version of FFmpeg. In turn you can use SMPlayer as mpv front-end.

4 Limitation

Known limitation on current implementation

• Does not support any features of VP9 that only supported by matroska container (alpha, WebTTV, etc, etc)
• No VP9 codec private information