[Ffmpeg-devel] Ambisonic decoder
Sat Feb 24 02:55:03 CET 2007
About one month ago I started a research on how to encode a full
surround sound track of a movie into 128 kbps. Currently, soundtracks
of this bitrate are encoded in stereo using either mp3 or ac3 or aac.
There were then two issues here: a better sound compressor and channel
coupling. Finally I have chosen Ogg Vorbis and Ambisonics, and they
show such a well compressed, surround sound track can be done and then
played back with mplayer (-af pan). The encoder is already done and
can be taken from http://www.ambisonicbootlegs.net/Members/qduaty.
Unfortunately, MPlayer does not distinguish between 5.1 and 3
channels, applying the same filters for both, and Ambisonics itself
can have 3-16 or even more channels, depending on source and its
soundfield's precision. There are many existing music recordings that
are stored this way; as the results are much better than with stereo
or even 5.1, it can be clearly stated that this technology has future
and will grow in strength.
My current goal is to add a basic Ambisonic decoder (with or without
shelf filters) to lavc so it could affect both mplayer and ffdshow.
This way we will give people an opportunity to encode movie sound
tracks in a proper way :P, i.e. using open technologies.
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