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Questions and Answers

Please read these before reporting a bug, complaining about missing features or misfeatures, sending patches etc. Some of the points below are here to state the developer's concepts about what this software is and what it is not. Some other issues are also covered.


Can I play CD's, or listen to streaming media (HTTP, *cast)?

Not with this program. Aqualung is designed solely to play audio files within the reach of your local computer filesystem. Note: you can have a computer that stores your music and listen to it from all other machines on the same LAN by mounting it via NFS. (I have actually verified that such setup works flawlessly.) If you have CD's, you should grab them onboard and encode them with FLAC (that's what I do) or Ogg Vorbis (if you don't mind the lossy compression). Then add the music to your Music Store, and you should never need to touch that CD again. It will serve well as an archive copy. If you really want to directly play a CD, you need (guess what) a CD player program.

Please note that while Aqualung already provides a lot of features in its present form, it is still under development. These features are considered useful, and will likely be implemented sometime. They just need more investigation (and the developer's time is limited).


Do I really have to type in all the track titles by hand? Haven't you heard about freedb.org?

I have, but it's not as trivial as it may seem. (Let me not go into details about it now. Before you ask, it has very little to do with my personal skills; I can handle UNIX network programming.) For now, there is no freedb or other such support in the program. I am strongly considering this functionality to be added, and it is likely to happen sometime. Don't hold back your breath, though. If you want to help, I am open to discussions and happy to receive patches.


The program uses large amounts of CPU. Why?

If you use Sample Rate Conversion on a not too fast machine, problems may arise when choosing a high quality converter. (That means choppy playback, as the computer can't do the processing in real time.) High quality resampling with bandlimited sinc interpolation is just very CPU intensive. If you have a slower machine, try running the "Fastest Sinc Interpolator". Not as CPU-hungry as the higher quality ones, but still not too bad to listen to. Also, if you have many LADSPA plugins running, you may run out of CPU power. There is really no need to run so much plugins. As a side note, some LADSPA plugins (those that have feedback loops in themselves, such as echoes and recursive filters) may have so-called denormal floating point bugs that cause exponential increasing of the CPU usage until all of it is used up. It usually occurs when the signal level gets very low at song endings and such places. If this happens to you, try to track it down to a single plugin, and contact the author of that plugin.


I did hear very short dropouts when changing tracks! You lied!

I did indeed. But you were listening to MP3's, weren't you? If not, send me a bug report. If yes, read on. MP3 (MPEG 1 Layer III audio compression) is an old format now completely obsoleted by better ones (notably Ogg Vorbis). One of the shortcomings of MP3 (and MPEG Audio in general) is that you cannot encode audio streams of arbitrary lengths. To encode, the stream has to be padded so its length will be an integer multiple of the MPEG frame length (so as to encode it into an integer number of frames). So encoders pad the ends of tracks, and when they are played back, the silence is also decoded since there is no way to tell where in the last frame audio stops and padding begins. The MPEG decoder library returns the decoded stream with the silence at the end; the silence is not inserted by Aqualung. This is a shortcoming of MPEG Audio, and you won't experience it with Ogg Vorbis or FLAC.


Seeking in MP3 files is a bit fuzzy. Sometimes when I release the seek slider, it jumps to another position and plays from there.

Another MP3 issue. MPEG Audio has no built-in support for seeking; a decoder would have to read through the whole stream before actually playing anything and build a seeking table internally that contains the legal positions where seeking is possible. At present, Aqualung just seeks the bitstream and hopes that the MPEG decoder will be able to recover not too far from the desired position. This mostly works for properly encoded files, but may fail badly on others. Please understand that I included MP3 support solely to deal with legacy issues; you should never encode newly ripped music into MP3 (use Ogg Vorbis instead). Therefore I'm not willing to spend much time on improving the MPEG playback interface; after all, you can playback the files without seeking (and seeking also works on most files, most of the time). However, if you have a patch, I will be happy to accept it.


The program was playing a track when I cleared the playlist. The playlist got empty, but the program is still playing. What the heck?

This is consciously chosen behaviour. The other possibility would be to stop playback every time the currently playing track is removed from the playlist. Instead of that, playback proceeds (which is natural, since once playback started, the engine can proceed with it regardless of the contents of the playlist). Playback will stop only when the track ends and playback would move to the next track. This gives you the possibility to change playlists without ever needing to stop playback.


Where is the spectrum analyzer? Where are the visualization plugins?

Dude, if you feel like gaining information about the spectral content of the music that's playing, you simply got to listen to it. No 20-bar "spectrum analyzer" will give you information of that density and accuracy. The human ear is one of the most sensitive instruments ever made, outperforming any ordinary measurement technology. Besides that, the author believes that music is for listening, not for viewing. If you want idiotic flashing lights that have no real connection to the sound but perhaps look nice to some people (that being the only acceptable excuse for their existance), go find some other program. Note that I will not accept patches that would add such (mis)features to the program.