]> The &krec; Handbook Arnold Krille
arnold@arnoldarts.de
 2002 2003 2004 Arnold Krille &FDLNotice; 2004-03-01 0.5.1 &krec; is a recording application for &arts;. It can be used to record any sound coming into or out of the computer. Some effects for dynamics are implemented as well as the possibility to play out what is recorded. KDE kdemultimedia KRec aRts recording frontend Introduction Why I wrote &krec; After working with &arts; for some time I realized that there is no recording application for it except the command line tool artsrec. I had to record a radio play some friends of mine wanted me to mix and master and I wanted to use &Linux; for the recording. So I started writing &krec;. What &krec; does &krec;'s function is quite simple. It connects to the &arts; server and records what is routed to it into files. These files are in a special &krec; format but it is possible to export to wave, ogg and mp3 files. But &krec; has much more functionality. You can do multiple recordings in one file even with overlaying functionality. Getting more info &reporting.bugs; &updating.documentation; A first glance at &krec; Here's a screenshot of &krec; Here is a screenshot of &krec; right after it started. The &krec;-mainwindow in detail At the top there is the menubar and two toolbars. The first toolbar contains some usefull items from the Files-menu, the second toolbar is shipped with important functions from the Play-menu. The middle has the important parts: On the left is the VU-Meter displaying the volume of the audiosignal currently recorded/played combined with a volumecontrol to adjust the level. The main part shows the file and consists of four parts. First at the top is the name of the file, the second shows the parts recorded in their chronological order and scaled length. It also allows to disable or delete parts via contextmenu. Below is the time line where you can see the current position and (by clicking) move to the position you want. The bottom of this block are two widgets showing the current position and the length in the timeformat you want. At the overall bottom there is another toolbar containing a compressor to edit the dynamics of your recording and a statusbar showing all kinds of messages. See for more info. Howto record This chapter contains some step-by-step tutorials which show you the way to go for some good recordings with &krec;. Recording from internal music The first thing to do is a recording from our favourite &kde; audioplayer. So start &noatun;, &juk; or &kaboodle;. We could use other players but they have to use &arts; for their output, otherwise recording is a bit more complex and beyond the scope of this section. So please jump over your shadow and select a song to play in one of this three players (all are shipped with kdemultimedia where you got &krec; from). In &krec; select the Audio Manager from the Tools-menu. There you will see at least a line for &krec;::In and a line for &krec;::Out. The second column says what type the item is, either play or record. The last column says where the sound for this item comes from or goes to. Currently the &krec;::In item is (should be?) connected to in_soundcard which is the input channel of your soundcard but as we currently want to record from the player and the player plays to out_soundcard, we click on the &krec;::In item to switch it to another source. Select out_soundcard from the upcoming window and click Ok. To learn more about the audio manager see . Now the VU-Meter in &krec; should flicker up and down in a way corresponding to the music your hear (if you don't hear sound you shouldn't expect the VU to show something). Now open a new file either by clicking on the first item in the toolbar or by selecting New from the Files-menu. Accept the quality settings for now or see for more info. Select Record from the Play-menu or press the R-key. After you are finished select Stop from the same menu or use the S-key. Saving works the standard way, if you are interested in exporting see . Thats it! Now you can hear your recording or export it (don`t forget to go back to the beginning). Recording from Line-In or Mic-In Recording outside-sources is a bit more complicated as it involves a lot of different applications and hardware devices. I am assuming your hardware is installed correctly, the drivers are working as they should and you are able to control the hardware volumes via &kmix;. In &kmix; you can also select channels for recording which basicly means that their signal is sent to the analog-digital-converter (short ADC) and can be read by the driver and applications. This works differently on almost all soundcards and drivers so you have to try a bit before you can be sure... Second important thing is that &arts; has to run in full-duplex mode. That means that &arts; is reading from the soundcard and writing to it at the same time. You have to start &kcontrol; and edit the soundsystem settings (or press Alt+F2 and enter kcmshell arts). On the second tab-page you have to make sure the checkbox for full-duplex is selected, clicking Apply restarts &arts; which means that you have to restart &krec; too. After these preparations the VU-Meter (see for more info) of &krec; should flicker according to the audio-signal you want to record and which you have selected for recording in &kmix;. Adjusting the volume to the right values is very important for usable recordings. If the amplification inside the soundcard is to high you get digital crackles because the ADC can only create values between a minimum and a maximum and if the signal is to loud it gets digitally clipped which ruins the recording. On the other hand if the volume is to silent you get the noise and hiss from the audio-hardware to loud into your recording. So you have to choose a middle-way so the signal is not to loud and gets clipped but not to silent to get lost in the noise of the hardware. Its almost always better to leave some headroom. Now you can adjust the level a second time in &krec; which then is a software amplification. Here it is best to use the compressor to equalize the differences between silent and loud parts a bit. More info on compressor usage can be found in . The remaining steps are the same as in from step four and following. So if you started with that section you should know it now. &krec; explained This chapter describes some parts and functions of &krec; in detail and gives some tips on usage. The items are sorted alphabeticly, not by importance. The Audio Manager The audio manager is used to connect the outputs from different applications to existing or new busses. A bus is some kind of a virtual signal distributor. Every play- or record-item can connect to exactly one bus but multiple items can connect to a bus. Example: The output of &noatun; can connect to the main out or any other bus. But multiple &noatun;s can all connect to the main out. The main window of the Audio Manager It contains three columns: The name of the item playing or recording sound. The type of the item either play or record. The bus the item is connected to. Click on an item and a dialog for choosing the wanted bus pops up. The Busdialog The main part shows all currently existing busses. Select one to send your audio to it or get your audio from it. Below you can create new busses to connect your item to. To record from an &arts;-aware-player and listening to what you actually record just create a new bus (test for example), connect your player to it (you wont hear anything now), connect &krec;::In to the new bus too and then turn on the Play Through. The Compressor If you are recording with a microphone you might notice that the level is sometimes almost clipped and sometimes very low especially singing or speeching voices. To correct this you can use the compressor. It simply reduces all sound that is over the given threshold by the factor given as ratio. Note that the threshold is logarithmic, a mid setting is already relativ low but thats very usable that way. Another note: ratio is at its highest turned to the left, the right end of the poti means no compression at all. As this reduces the loudness there is a output potentiometer to expand (or reduce) the sound. attack and release let you control the time after which the compressor reacts (the time going by after input first exceeds the threshold) and the time the compressor still reacts after sound is below the threshold. Test it while you are speaking into your microphone with Play Through enabled and you will hear the difference between the plain and a compressed version. Tips for compressor usage These are only tips. In the end the only thing that counts is how it sounds. So if it sounds as you want it, its probably the right setting. And don't hesitate to do some experiments. Normal speechMost times a single voice speaking for radio or television is very heavily compressed. Because the main problem of speech is that the level is perhaps the right way at the beginning of the sentence but probably not at the end. Additionaly the wordendings are less loud than the start. That makes it impossible to use spoken words without compressing it. Examplesettings: Short attack, mid-time release, low threshold, very high ratio. Mastering 1: Limiting the levelTo just limit peaks but not compress whole dynamics use a high threshold, a high ration, a short attack and a short-to-mid release. This protects your recording from some internal digital distortion and, with the treshold a bit lower, removes rare (and perhaps unwanted) peakes and gives more room for the actual recorded signal. Mastering 2: Doing real masteringDoing real Mastering of music is difficult and depends totally on your hearing and the music that is to be mastered. Normally you will use fast attacks sou you get the level reduced fast enough at the bass drum beat. On the other hand you don't want the music to be pumping up and down just because of the bass drum beats so you select a longer release. The compression factor shouldn't be much. Ideally you would plug a limiter after the compressor to be free of clicks and clippings. Single InstrumentsThese settings depend on the instrument. While recording it is wise to use a limitersetting. Final tipUse your ears and do some practicing. Anything is allowed if it sounds right! Configuration Two pages are available at the configuration. The first one is for general settings and explained in this section. The second is about the default quality settings and the same as described in . General settings Editing general &krec; settings. The first part are settings controlling the way time and positions are displayed. The style "Plain samples" just shows the number of samples, the next one has optionally hours, minutes, seconds and samples. The third style is the same as the second except that it shows frames instead of the samples. The fourth style shows the size in megabyte and kilobyte and usefull for controlling diskspace. On the right side of the styles you have the opportunity to select the number of frames forming one second. The checkbox below makes the timedisplays be more verbose and showing the unit within. If you want to restore the tip of the day at startup you can do so with the next checkbox. The button below it brings back all the messages where you did select "Don't show this message again", mostly messages fom the export functions. Exporting
An anonymous fan of &krec; Your app is very cool, I use it all my day but it really lacks exporting to wave/mp3/ogg!
Here it is: the definitiv export functionality for &krec;. The available export formats vary on the libraries found at compiletime, all currently available ones are described in the following sections. Selecting the wanted exportplugin is done via the filename: You select Export File... from the Files, choose the filename for the exported file and its extention and the plugin is determined from your extention. The list of extentions in the dialog also shows which exportplugins are available. For understanding the general usage of export: Technically exporting works like playing. That means that you have to go to the position where you want to start the exporting before doing it. It also means that you can see the progress of the exportation from the current position marker moving forward. And it means that in the future its possible to export every selection you like just like playing only a selection. Exporting to Wave (*.wav) The simpliest exportplugin. It exports your &krec; file to a wave file with the quality settings you made for the whole file. Exporting to MP3 (*.mp3) Maybe the most-wanted export possibility. This one exports your &krec;-file into a mp3-file. The qualitysettings you set up in &kcontrol; section Sound & Multimedia / Audio CDs are used in this version since &krec; also uses the same libraries as the audiocd:/-feature. Exporting to OGG (*.ogg) This one exports your &krec;-file into an ogg-file. The qualitysettings you set up in &kcontrol; section Sound & Multimedia / Audio CDs are used in this version since &krec; also uses the same libraries as the audiocd:/-feature. Play through For those who want to hear what they are recording there is the very useful Play-Through option in the menu Play. I advise using it as much as possible especially if you do things like using the compressor or other effects and want to control what actually is recorded. Be sure to not build a feedback loop while recording from out_soundcard and activating Play-Through. Such a loop is way to much for poor &arts; and it slows your system heavily down! You might kill &arts;... The reason is that &arts; calculates a network for audio for every sample (acually blocks of samples) and if on sample is build via a loop from itself &arts; has to calculate more than is possible. Quality settings The properties for new files This is the dialog for choosing the properties for new files. While creating a new &krec;-file this dialog is displayed and lets you choose some settings for the quality of the recordings. All of these settings have an impact on the size. The sampling rate is the rate which tells audiosystem how many samples to take during a second and is measure in Hertz (Hz) respectivly Kilohertz (kHz). The higher this rate the higher is the maximum recorded frequency. Since at least two samples are needed to rebuild a sinus-wave the maximum recording frequency is half of the sampling rate. The human ear is capable of hearing tones up to something between 10kHz and 20kHz depending on the age, little children are possibly nearer to 20kHz while normal adults have their maximum around 15kHz and elder people go down to 10kHz. But even without actually hearing the higher frequencies they still have an impact on what is heared and felt (corresponding keyword: psycho acoustics). The number of channels can be freely choosen depending on the task of the recording. If you are using a mono-microphone without applying a stereo effect you can safely choose Mono without the loss of data. The last part are the number of bits used for one sample, possible values are 8 and 16 bits. The more bits the more steps are available for the range from minimum and maximum signal. 8 bits are one byte so this can also be referred to as one byte or two byte samples. The space needed for the recording can be calculated in a very simple way: Its the sampling rate multiplied by the number of channels multiplied by the number of bytes per sample multiplied by the number of seconds wanted to record. Calculating the size of one minute CD quality For one minute (60 seconds) audio in CD quality (44100Hz, 16bits, stereo) the space needed is: 44100 * 2 * 2 * 60 = 1058400 Bytes = 10335.938 Kilobytes. That is around 10 MByte of data per minute. Always use the best needed quality! Reducing the quality later on is always possible, but enhancing the quality is not possible since then more data as available is needed. The last item above the button is a checkbox for using the entered values as defaults for every new file without showing this dialog again. As the same dialog is also available in the configuration to choose the standard settings, the "Use defaults..." checkbox is also accessible from there to get the dialog for every file back. VU-Meter As the compressor is probably not necessary for every task the vu-meter with its builtin volumecontrol is the most needed part of &krec; for recordings. It shows the actual level that is recorded to the file after the used effects and after the volume set with the control. If it is deep red most of the time the recording is probably clipped and doesn't sound nice. If it flickers around the bottom 2% its probably not much you will hear in your recording. For good recordings the level should be between -12dB and 0dB most of the time. Use the compressor for editing the dynamics of your recordings. See for more info. Credits and License &krec; Program copyright 2002-2003 Arnold Krillearnold@arnoldarts.de Documentation copyright 2002-2004 Arnold Krille arnold@arnoldarts.de &underFDL; &underGPL; Installation How to obtain &krec; &install.intro.documentation; Requirements In order to successfully use &krec; 0.5.1, you need &kde; 3.3. &krec; should be within your kdemultimedia package. As this package needs a running &kde; and &arts; too, everything should be fine. Compilation and Installation &install.compile.documentation; &documentation.index;