[FFmpeg-user] [FFmpeg-devel] Codec Routing

[Timothy Gu]

Hi,

This question belongs in ffmpeg-user at ffmpeg.org mailing list. I have
CC'd this mail to that mailing list, and please don't reply to
ffmpeg-devel anymore.

On Thu, Aug 21, 2014 at 4:55 PM, Chuck Burfoot <chuck at burfoots.com> wrote:

> I build with --enable-libvpx. I was keenly interested in the ability of
> libvpx to create/encode "webm" with alpha.

So you only want encoding with libvpx? The questions below are all
about decoding.

[...]

>
> So I dumped --codecs and low and behold
>
> DEV.L. vp8                  On2 VP8 (decoders: vp8 libvpx ) (encoders:
> libvpx )
>
> DEV.L. vp9                  Google VP9 (decoders: vp9 libvpx-vp9 )
> (encoders: libvpx-vp9 )
>
> There's 2 DECODERS for vp8 and vp9 and the 'internal' one is used first !
>
> Isn't that a build bug?

No. The internal decoder is much faster than libvpx (See
http://x264dev.multimedia.cx/archives/499), and not many people use
alpha in VP8. That's why we made it default. If you really want to use
libvpx to decode vp8, use something like:

ffmpeg -c:v libvpx -i INPUT ...

> Do I need to do a --disable-vp8, etc?

If you want to force libvpx decoding at all times and disable the
internal VP8 decoder, do --disable-decoder=vp8.

Timothy