Phil's Blog

Yesterday, I did few tests between ogg vorbis and faac audio codec at low bitrates. So, the main thing to remember is :

1. ogg vorbis CBR encoding is really slow !

2. ogg vorbis VBR encoding is twice faster than the CBR methode

3. faac encoding is twice faster than vorbis VBR methode

4. under 80kb/s, audio is not really good. So, for low bitrates movies, you should use audio at 80kb/ at least.

5. faac add some strange audio artefact, which are away from ogg vorbis. So, you should wait for best result with FAAC codec and use OGG VORBIS today for your low rates movies.




About the container, the only one which works with a X264 video track and a VORBIS audio track is matroska container (MKV). It is pretty long to do such files. The main opertions are (under linux) :

1. ffmpeg -i movie_source.avi -acodec pcm_s16le -vn audio.wav # -vn means no video, and use pcm_s24le if your audio source is 48kHZ

2. ffmpeg -i movie_source.avi -an -vcodec copy video.avi # -an means no audio

3. compress the audio track with oggenc (ogmtools package)

oggenc \

--resample 44100 \ #optionnal

-q2 \ #around 80kb/s, 10min for 40min audio track on a 1GHz CPU

-o audioq2.ogg

audio_src.wav

4. compress the video track with avidemux

4.1 x264 codec

4.2 2 pass

4.3 450kb/s average

4.4 minq=25 / maxQ=51

4.5 resolution mplayer filter/ width=480/ lanczos #this resolution is a good compromise

4.6 MP4 container

5. mkvmerge -o movie_out.mkv -A video.mp4 audioq2.ogg #mkvtoolnix package, you can add other audio tracks too.



Finally, for a 40min TV show :

1. the audio filesize : ~26Mo,

2. the video filesize : ~66Mo,

3. the final movie filesize : ~92Mo.



Enjoy ;)