Release: libfishsound 0.9.0

Now libfishsound 0.9.0 supports FLAC, the Free Lossless Audio Codec. The patches were originally contributed by Tobias Gehrig in 2004. There hasn't been much use of Ogg FLAC, whereas FLAC in its native encoding is very popular. However, the point of the Ogg mapping is to allow FLAC to be used in parallel with other codecs, in particular as the audio codec for video files. The combination of Theora video and FLAC audio can be very useful for music videos, where you might not care too much if the image has lost some quality but you want the sound to be as good as possible.

However, creating such a file isn't so easy. Let's say you have a source video, like GrooveTV #204 - Jacob Fred Jazz Odyssey. I took the MPEG-1 file as recommended; for clarity, let's call it source.mpg. To make a video to test on, I did:

ffmpeg2theora source.mpg
to encode the video into an Ogg file containing Theora video and Vorbis audio. This produces source.ogv.

oggzrip -c theora source.ogv -o video-theora.ogv
to extract only the Theora video track, into video-theora.ogv.

mpg123 -w source.wav source.mpg
to extract the audio to a wav file, source.wav. Here the audio in the source material was encoded as MPEG I layer II; obviously if you were producing a music video, you'd skip this step and encode FLAC from the original recording. I didn't have that here, and I just wanted a file I could test on.

However, at the least this step means that no further artifacts are introduced into the audio, other than those which were present in the MPEG encoding. If the only source material you have is already encoded, you don't want to degrade it further by re-encoding it with a different codec.

flac --ogg source.wav -o audio-flac.oga
to encode the audio. This produces an Ogg FLAC file called audio-flac.oga.

oggzmerge video-theora.ogv audio-flac.oga -o final.ogv
to merge the video and audio tracks into the final Ogg video file, final.ogv.

Note that we're using the recently recommended file extensions for Ogg video and audio.

If you know an easier way to create Ogg Theora+FLAC files, please leave a note in the comments :-)