Ecasound User's Guide
Contents
1. Ecasound will fail if the currrent values for these parameters do not match the ones used by the JACK server In other words you have to correctly set the buffersize with b xxx and sampling rate with f bits channels srate and possibly using the resample audio object This is the first thing to check if communication with JACK does not work Future versions of Ecasound will hopefully solve this problem This issue is covered by Ecasound development item edi 31 Support for dynamic sampling rate and buffersize changes 7 6 6 Deprecated JACK input output syntax Ecasound 2 5 and older supported jack_alsa jack_auto and jack_generic object types but these are now replaced by a more generic jack interface The old variants this work but are now considered deprecated they work but may be removed in a future Ecasound release 24 Chapter 8 Miscellaneous 8 1 Security Considerations When given the r option raise priority Ecasound tries to raise its scheduling priority to so called SCHED_FIFO realtime scheduling and to avoid swapping locks all its memory To do this root privileges are required So either Ecasound has to be run as root logged in as root or using the sudo program it has to be installed with the suid root bit set or otherwise be granted necessary privileges to turn on real time schedule see below Now is this a safe thing to do Although there are no known v2. Updated the Current position section Chapter 3 Introduction 3 1 What is Ecasound Ecasound is a software package designed for multitrack audio processing It can be used for simple tasks like audio playback recording and format conversions as well as for multitrack effect processing mixing recording and signal recycling Ecasound supports a wide range of audio inputs outputs and effect algorithms Effects and audio objects can be combined in various ways and their parameters can be controlled by operator objects like oscillators and MIDI CCs A versatile console mode user interface is included in the package Chapter 4 Ecasound concepts 4 1 Audio object udio objects are used to transfer audio from and to Ecasound Usually au dio objects are either files like wav mp3 or ogg or devices soundcard in put output There are also some special audio object types for transferring data between applications 4 2 Chain Chain is the central signal flow abstraction In many ways chains are similar to audio cables You have one input and one output to which you can connect audio producers and consumers like guitar and amplifier for instance But there are some differences First it s possible to attach chain operators usually effects to chains This is somewhat like replacing one cable with two and putting an effect box between them but with chains it s just easier A second important difference is that chains can tr
3. case the gate is opened when the RMS volume goes over the 11 2 threshold and closed when RMS volume falls below 5 In the sec ond case both entry and close thresholds are 5 peak volume 7 5 LADSPA plugins Ecasound supports LADSPA effect plugins Linux Audio Developer s Simple Plugin APT See ecasound 1 man page and the LADSPA web site at www ladspa org for more information 7 5 1 Ecasound is not able to find any LADSPA plugins I have installed Just installing the LADSPA SDK www ladspa org should be enough The plugins themselves are stored in shared library files so They are usually stored in usr local lib ladspa To test whether Ecasound finds the plugins issue echo ladspa register ecasound c You should get a list of all installed LADSPA plugins If this doesn t work you need to make sure Ecasound is compiled with LADSPA enabled ie ladspa h header was present when Ecasound was compiled The precompiled rpm binaries have this but if you ve compiled Ecasound yourself you should recompile after installing the LADSPA SDK Also check Dave Phillips great article on Oreillynet http www oreillynet com pub a 1linux 2001 02 7 6 JACK Audio Server JACK is system for handling real time low latency audio It allows multiple independent applications to access the system audio hardware and also to route audio between applications JACK is different from other audio ser
4. e source audio object name string read write e offset insert audio object at offset time read write e start position start offset inside audio object time read e length how much of audio object data is used time read e looping whether to loop sample data true or false read All time values are interpreted as seconds need not be an integer but can be given as a decimal number e g 1 05 However if the value is an integer number and has a postfix of sa e g 44100sa it is interpreted as time expressed as samples in case of a multichannel stream time in sample frames 7 2 3 Example of ewf use Let s look at a simple example ewf file test ewf source test wav offset 5 0 start position 2 0 length 3 0 looping true c t 17 Now what happens when you issue ecasound i test ewf o alsa Because of the offset definition the first 5 seconds will be silent After that ecasound will start to read data from test wav But as start position is not zero ecasound will skip the first 2 seconds After 8 seconds has passed offset length ecasound will loop back to start position This looping will continue until the user interrupts the operation 7 3 Effect presets 7 3 1 General Ecasound has a powerful effect preset system that allows you to create new effects by combining basic effects and controllers Presets can be stored
5. erc 1 2 epp 0 a 2 i monofile2 wav erc 1 2 epp 50 a 3 i monofile3 wav erc 1 2 epp 100 a all f 16 2 44100 o alsa The actual signal chain is something like monofilel wav 1 erc epp A monofile2 wav 2 erc epp alsa m monofile3 wav 3 erc epp N gt mono channel The critical points to notice are 12 e ecasound automatically notices that the three input files are mono files so chains are initialized with one mono input e chains contain mono signal until erc operator which transforms the chain into a stereo chain by copying the data from chl to ch2 e now epp works as expected sets the stereo balance for one input e chains are mixed to the soundcard device channel wise If you leave out the erc operators chains will still be converted to stereo as epp is a stereo operator but on each chain only the first channel left will contain any audio from the input files 5 5 4 Filenames with commas not handled correctly There are some pitfalls in how commas in filenames are handled by ecasound If you have a filename foo bar ogg the following will not work ecasound i foo bar ogg o alsa The only way around this is to escape all the commas with backslashes ecasound i foo bar ogg o alsa The backslash has to be a double backslash as the shell strips one of the back
6. into separate files or they can be stored into a global database Either way the preset format is the same also see man page the same file format and syntax is used preset name effects controllers effects controllers Effects and controllers are specified using the EOS syntax the same syntax that is used for parsing command line options ea 100 k1 1 0 100 5 etc The pipe character is used to separate parallel chains Just like in shell scripts the character can be used to spread definitions across multiple lines 7 3 2 Example of preset use Ecasound effect presets are in fact small Ecasound engines that behave just like native effects Here s an example of a multi chain effect preset cut file bassbooster ecp let s put the low freqs into one chain and high freqs in another bassbooster ef1 2000 ea 200 efh 2000 ea 50 note the sign separates parallel chains cut Once defined you can use the preset in the following way Cut ecasound a 1 i some mp3 pf bassbooster ecp a 2 i another mp3 pf bassbooster ecp a 1 2 o alsa cut 18 When separate files are used the pf name option Ecasound always loads the first preset it finds If the file contains more presets additional key value pairs they are ignored An alternative way to define presets is to put the definition in the global preset list usually in usr local share ec
7. Ecasound User s Guide Kai Vehmanen 19042009 Contents 3 2 Document history 3 1 What is Ecasound 2 2 m m nn nn ee E a 2 Sok Ch one ene ee 4 6 Ecasound Control Interface EC 4 7 Ecasound Interactive Mode EIA 4 8 Ecasound Option Syntax EOS A aoa o o 00 00 ON NNN 5 1 Where to start s s soe ses sa saca aedade kn a odai 10 A ee A ore 11 See eee eee ee ere 5 5 2 Can I use multiple soundcards 5 5 3 Problems with panning mono filey 12 5 5 4 Filenames with commas not handled correctly 13 6__User interfaces and Application 14 be ae ee An ea A es eg eB ee 14 6 2 Ecasig nalvie TES de a te wey ds Sue La oan er A QU Berea A ad 14 bese a GER E ty es Ags Sa ee een ee cos 14 6 2 2 Further Reading 00000000 0G 15 6 3 Beat old ses mm ede an Sa RA EH A a we eee 15 16 bk gen Pek he a ee Oe 16 711 Example of usq a a a a en 16 7 2 Ecasound Wave Files the EWF ewf format 17 T21 General aa he ete ok ea A De ae 17 7 22 File formal ua 2 a0 0 ann E AR ww raa 17 7 2 3 Example ofewfusd 2 00004 17 713 Effect presetg 2 2 2 2 18 7 3 1 General de dr da ne re A A Re a 18 7 3 2 Example of preset use 7 3 3 Preset parameters 222 2 ee a 19 7 3 4 Parameter descriptors 2 22 2 a 2 nn 19 74 Gate Opera
8. ansport multiple channels of audio It s possible to attach mono stereo or 24ch or bigger audio feeds to one chain Also all chain operators can handle these multichannel streams In addition to chain operators chains also have separate mute and bypass functions 4 3 Chain operators and controllers Chain operators are used to process and analyze sample data They can be divided into gates converters signal analyzers and to traditional effects like reverbs delays and filters It s also possible to attach special controller objects to chains These con trollers are used to control chain operator parameters The typical examples are various oscillators and MIDI continous controllers knobs sliders etc found on MIDI devices Both types of objects are attached to chains The term chain object refers to all objects that can be attached to chains ie operators and controllers 4 4 Chainsetup Chainsetup is the central data object All other objects inputs outputs chains etc are connected to some chainsetup Many chainsetups can exist at the same time during one session but only one of them can be in use In Ecasound documentation the term connected is used to describe a chainsetup that is in use Another important chainsetup concept is that of a selected chainsetup All editing operations are done on the currently selected chainsetup It is possible to have one chainsetup connected currently processing audio wh
9. asound effect presets Once you ve added a line defining bassbooster you can use it like cut ecasound a 1 i some mp3 pn bassbooster a 2 i another mp3 pn bassbooster a 1 2 o alsa cut 7 3 3 Preset parameters Parameters of operators belonging to a preset can be exposed as preset paramters Example cut preset definition f_res_lowpass ef3 41 1 5 0 7 cut In the above example the lowpass filter cutoff is exposed as a parameter of the f_res_lowpass preset The preset can be used just like any other Ecasound operator The following two commands will results in identical output cut ecasound i foo mp3 o alsa pn f res lowpass 800 ecasound i foo mp3 o alsa ef3 800 1 5 0 7 cut 7 3 4 Parameter descriptors Ecasound preset parameters can be described using the following set of descrip tors pd name_of_preset preset description ppn parl parN parameter names public params ppd vali valN default param values ppl vali valN lower bounds for param values ppu vali valN upper bounds for param values ppt flagsi flagsN special flags for param N i integer 1 logarithmic o output t toggle The option can only be used inside preset definitions in effect_presets files or individual ecp files An example preset parameter definition 19 cut f_two_filters ef1 800 ea 1 efh 800 ea 2 pd Paralle
10. cting the chainsetup when issuing commands such as cs connect or start 5 3 Chain operators and controllers The best place to start is to read through the lecasound 1 man page which contains documentation for all native Ecasound chain objects 5 4 Configuration User preferences are stored in ecasound ecasoundrc See the ecasoundrc 5 manual page for details By default files for effect presets and oscillator presets are in usr share ecasound 5 5 Common problems 5 5 1 I get occasional audio dropouts during operation How to get rid of them Check http www oreillynet com pub a linux 2000 11 17 low_latency html where you ll find a very good article written by Dave Phillips on Linux low latency issues If you are in a hurry or desperate here s a quick list of things to try e Tune your disks see the article e Enable ecasound s double buffering system by using the z db option note this is only necessary with Ecasound 2 0 x and older e Tf you re still having problems run ecasound as root or with SUID bit set and use ecasound s r option This will raise ecasound s scheduling priority to realtime SCHED_FIFO with ecasound 2 1 and newer just run ecasound as root and it will take care of tuning the settings e Try increasing ecasound s buffersize with the b sample_frames option Something like b 4096 should do the trick e Tf all else fails try the various low latency kernel patches a
11. detailed information the available commands see ecasound iam 1 man page 4 8 Ecasound Option Syntax EOS One very notable feature of the console mode ecasound program is its command line option syntax You can do pretty much everything from the command line But it doesn t end with the console mode ecasound In fact interpreting these options is located in the main libecasound library and is very closely tied to the interactive mode As a result the same syntax tokens that look like prefix arg1 arg2 argN is used in various parts of libecasound Note that if any of the arguments con tain commas those arguments need to be enclosed in double quotes for example prefix ar gl arg2 Following is a partial list of the places where EOS syntax has been used e parsing command line options e the interactive mode as arguments to the cs option command 2 1dev4 and newer e saved chainsetup files ecs format e effect preset definitions see for example usr share ecasound effect_presets e generic oscillator definitions see for example usr share ecasound generic_oscillators Chapter 5 Using 5 1 Where to start There s no one single right way to use Ecasound You can use it as a simple glue component for doing tasks that aren t handled by other applications you are using or because Ecasound does these tasks more easily or better even But Ecasound can also serve as the centr
12. dora 20 741 Example of use A 7 5 LADSPA plugins eda a fete et QE aan NR ee 121 7 6 6 Deprecated JACK input output syntax 8 Miscellaneous 25 8 1 Security Considerationd ooo e En nn 25 Chapter 1 Preface This document describes Ecasound from the user s point of view In addition to the actual user client programs all essential Ecasound library concepts and features are also discussed To avoid duplicating documentation I ve used ref erences to other sources whenever suitable For instance Ecasound s man pages are a very good and up to date source of information They are also available in HTML format If not otherwise specified all documentation refers to the latest Ecasound version Chapter 2 Document history 19 04 2009 Removed duplicate Ecasound history section and added more web URLs pointing to other sources of documentation 31 01 2009 Lots of minor improvements in preparation for 2 6 0 release 29 01 2009 Updated JACK Audio Server section to match the changes in 2 6 0 release 05 08 2008 Fixed a bug in example of loop device usage 09 03 2008 Updated the EWF file section Replace uses of dev dsp with alsa in many examples 06 12 2006 Added notes concerning quoting EOS arguments containing commas 04 06 2006 Some minor improvements to the text Updated the descrip tions of realtime lsm and rlimits rtprio mechanis
13. dule is a loadable extension for Linux 2 6 kernels It selectively grants realtime permissions to specific user groups or applications Unfortunately Re altime LSM does not yet come with the standard Linux kernel so you need to install it separately A more recent approach and one that might be adopted by popular GNU Linux distributions is the rtprio extension to Linux resource limits See for a good overview of this approach and how it compared to the LSM mechanism described above 26
14. e f bits channels srate to set how many channels to record from the sound device using JACK As described in the ecasound 1 man page the parameters to f may be overridden by the audio objects In case of JACK the server always sets the sampling rate and also the sample format is fixed to 32bit floats Because of this the above two examples achieve the same result but you may find the latter command more readable It is possible to add another f before o foo wav if you want to write the file in a different format For example to convert the sample format to 16bit fixed ecasound f f32 2 i jack system f s16 2 o foo wav 7 6 2 More Advanced Port Creation Ecasound also offers the following alternative ways to create input and output ports ecasound i foo wav o jack ecasound i foo wav o jack remote client ecasound i foo wav o jack remote client local portprefix ecasound i foo wav o jack local portprefix ecasound i foo wav o jack multi remote client port 1 system port 2 ecasound i jack o foo wav ecasound i jack remote_client o foo wav ecasound i jack local_portprefix o foo wav 22 See ecasound 1 manual page for descriptions of the jack multi audio object and the variants of jack usage 7 6 3 Transport Control u Transport controls are functions like start stop seek etc that are com monly available in audio applications that maintain some ki
15. e of your studio setup doing everything from effects processing to multitrack recording and mixing This flexibility doesn t come for free It s difficult to describe Ecasound s fea tures in a few phrases Because of this new users are encouraged to start from the Examples page at http nosignal fi ecasound Docunentation examples htsl It isn t a perfect introduction and definitely shows only one way to use the soft ware but it does give an overall view of what can be done and more importantly it shows that many tasks are actually quite simple to do 5 2 Rules for creating and modifying chainse tups Here are a few rules that help writing valid chainsetups Whether you are editing chainsetup files ecs some graphical frontend just using command line options etc these rules always apply e Every chain has exactly _one_ input and _one_ output e All inputs and outputs must be connected to some chain e For every input output there is one and only one definition example i file wav e All routing from and to chains is based on selecting a set of chains and then specifying an input or output example a 1 2 i file ext 10 e All audio copying and mixing is done channel wise If you attach a 4 channel input and a two channel output to a chain that chain will have 4 channels of audio but only the first two channels will be written to the output file Note that these rules are checked only when conne
16. erstand how Ecasound and JACK states relate to each other When an Ecasound chainsetup is connected EIAM command cs connect a connection is established with the JACK server and all the JACK ports in that chainsetup are registered to it Once Ecasound s engine is launched with EIAM command engine launch connections if any are specified are made to the ports of other JACK clients In this state Ecasound is ready to process incoming transport state and position changes When Ecasound processing is started either with start or by an incoming transport event Ecasound s engine runs as a node in the JACK system When 23 processing is stopped either with stop or by a transport event Ecasound s engine is not run Any connections initiated by Ecasound to other clients are disconnected once engine halt is issued and engine operation is stopped Connection to the remote JACK server as well as unregistering any ports is performed when chainsetup is disconnected cs disconnect Note Normally you don t need to go through all the steps one by one Instead issuing start will automatically connect the chainsetup and launch the engine Similarly cs disconnect will stop processing and halt the engine if needed 7 6 5 Troubleshooting Ecasound v2 2 and earlier don t have the capability to change the engine buffer size and sampling rate dynamically during processing As a consequence run ning
17. gain check the article 11 There has been a lot of discussion about tuning your system for better per formance on linux audio dev and linux audio user mailing lists You can browse the list archives at http www linuxdj com audio lad archive php Here are links to selected messages from the ecasound list archives e Tuning parameters for reliable recording http nosignal fi ecasound list 2005 04 0038 html e Smart Buffering http nosignal fi ecasound 1ist 2001 10 0020 htm1 e Ecasound for Recording http nosignal fi ecasound 1ist 2001 06 0016 html 5 5 2 Can I use multiple soundcards This is possible but there are some issues you should be aware of If you try us ing multiple cheap soundcards to get more simultaneous inputs for recording it s likely that the resulting streams will not be in sync This problem is explained in detail in the Linux Audio Quality HOWTO section Notes on Full Duplex Recording and Other Realtime Issues http karmak org archive 2003 02 audio_quality_HOWTO htm The original page at http www linuxdj com audio quality is no longer available 5 5 3 Problems with panning mono files In situations where you need to convert mono audio objects to multichannel objects Ecasound can behave in a somewhat unexpected manner For instance the correct way to set panning for three individual mono input files and mix the resulting stereo output to soundcard is ecasound a 1 i monofilel wav
18. ile editing another chainsetup that is selected for editing Loading and saving chainsetups is the primary mechanism for storing and restoring state information When saving to files the ecs file format is used The file syntax uses the same notation as Ecasound s console and command line interface This makes it easy to edit the chainsetup files outside Ecasound either manually or using external utils See ecasound 1 man page for details 4 5 Current position Information about current position is only stored for audio objects and chain setups When you change chainsetup position all audio objects are affected On the other hand positions of different audio objects can be changed indepen dently 4 6 Ecasound Control Interface ECI Ecasound Control Interface is an API for application developers who want to take advantage of libecasound in their own apps See Ecasound Control Inter face Guide and Ecasound Programmer s Guide for more information 4 7 Ecasound Interactive Mode EIAM Most of Ecasound s functionality is located in one central library libecasound One thing that this library provides is a simple interpreter which can be used for controlling Ecasound This mode of operation is better known as Ecasound s Interactive Mode EIAM The most common frontend for the Interactive Mode is the console mode Ecasound program You can enter its Enteractive Mode by issuing ecasound c For more
19. l_highpass_and_lowpass_filters ppl 0 0 ppu 1000 ppd 100 100 ppn lowgain highgain cut The above preset ftwo_filters has two parameters which are described using the pd descriptor Recommended lower and upper bounds for the pa rameters are defined with ppl and ppu descriptors Default values for the parameters are specified with ppd 7 4 Gate operators Gates are just like any other chain operators They are assigned to a chain and process passing audio data buffers One special feature of gates is the ability to crop sections of audio files for instance to achieve automatic volume based cutting of audio streams 7 4 1 Example of use The following sequence cuts the section 60 00 sec gt 61 00 sec from guitar wav into gate test wav cut IN 1s la guitar wav rw rw r 1 kaiv kaiv 15790124 Sep 30 23 27 guitar wav IN ecasound i guitar wav o gate test wav gc 60 1 IN ls la gate test wav rw rw r 1 kaiv kaiv 180268 Dec 12 22 13 gate test wav cut The threshold gate is used similarly cut IN ecasound i gate test wav o gate test rms wav ge 11 2 5 1 ecasound i gate test wav o gate test peak wav ge 5 5 0 IN ls la gate wav rw rw r 1 kaiv kaiv 163884 Dec 12 22 18 gate test peak wav rw rw r 1 kaiv kaiv 143404 Dec 12 22 17 gate test rms wav rw rw r 1 kaiv kaiv 180268 Dec 12 22 13 gate test wav cut 20 In the first
20. ms 25 04 2005 From now on only major changes are logged to this changelog section For detailed change history refer to CVS history 23 04 2005 Started using the hevea style package and converted all links to use the hevea macros resulting in real hyperlinks in the HTML output Renamed the section Security considerations when running with root privileges to shorter Security Considerations added info about Realtime LSM module 01 04 2005 Updated Ecasignalview documentation 30 03 2005 Added sections on Preset parameters and Parameter de scriptors 11 12 2004 Added section Filenames with commas not handled cor rectly 18 12 2003 Many typo fixes and other corrections from Eric Rzewnicki 18 11 2003 Typo fixes 20 08 2003 Capitalize Ecasound in all cases where talking about the software package not the console mode user interface Updated JACK documentation with a description of JACK and Ecasound states 13 08 2003 Updated documentation concerning JACK transport func tions 31 10 2002 Few section layout bugs fixed 30 10 2002 Added JACK documentation minor layout changes 17 10 2002 Updated Ecasound overview 17 07 2002 Added documentation for ecasignalview 18 05 2002 Fixed a few typos 21 10 2001 Added material from the Ecasound FAQ 21 10 2001 Added this history section Document was restructured and all major chapters reviewed 01 02 2001
21. nd of current posi tion JACK s transport control interface allows controlling the transport state of all the apps connected to one JACK server from a single application Ecasound can support this functionality in four different modes notransport send recv and sendrecv By default Ecasound will both send and reveive transport events position and state to other JACK clients mode sendrecv ecasound c i null o jack To use transport control in Ecasound you have to have at least one published input or output JACK port Here we publish one null output port After giving the initial engine launch command in Ecasound interactive mode you are now able to use further EIAM commands to control all other JACK apps connected to the same server Commands like stop setpos 20 rw 10 fw 10 and so should affect other apps By default Ecasound doesn t react to outside transport control To enable this ecasound c i foo wav o jack system G jack eca_slave recv After giving an initial engine launch to Ecasound you should now be able to use other JACK apps to control Ecasound s playback of foo wav To combine external control with the ability to control the transport from ecasound s user interface ecasound c i foo wav o jack system G jack eca_slave sendrecv 7 6 4 JACK and Ecasound states To have a good understanding of the overall system it s important to und
22. o associate loop inputs with correct loop outputs ecasound a 1 i some mp3 a 2 i another mp3 a 1 2 o loop 1 a 3 ea 200 i loop 1 o alsa cut Both inputs are eventually routed to chain 3 where a ea 200 is applied to the signal This does have one downside loop device adds latency b x gt latency of x frames 16 7 2 Ecasound Wave Files the EWF ewf for mat 7 2 1 General Ecasound Wave File ewf is a simple wrapper format for controlling other audio objects Ewf files are useful for offsetting or time shifting audio files for instance play a short audio clip in the middle of a long multitrack mix for minimizing diskspace usage during multitrack recording output offsetting and looping Starting from Ecasound version 2 5 0 similar functionality is provided by special purpose audio object types audioloop audioselect and others You may choose between EWF and these audio object types based on your specific needs See ecasound 1 man page and the Examples web page at http nosignal fi ecasound Documentat for many examples of using these Writing to EWF file is nowadays considered to be a deprecated feature and it may be removed in a future release 7 2 2 File format Ewf files are stored in ascii format The syntax is based on key value pairs The same syntax is used with Ecasound resource files See lecasoundrc 5 man page for detailed info Currently recognized ewf keywords are
23. slashes away before passing the string to ecasound 13 Chapter 6 User interfaces and Applications For a complete list of user interfaces and applications built on top of Ecasound visit Ecasound s web site at http www eca cx 6 1 Ecasound The standalone program ecasound is the primary user interface for Ecasound See ecasound 1 man page and the Examples web page at http nosignal fi ecasound Documentation 6 2 Ecasignalview Ecasignalview is an utility program for monitoring signal amplitude and peak statistics It s primarily used when adjusting signal levels for recording 6 2 1 Basic use The basic use scenario is to record audio from a soundcard device visualize it with vu meters and write it to a null output OSS drivers or properly installed ALSA 0SS emulation ecasignalview dev dsp null native ALSA mode recording from the default device ecasignalview alsa default null It is possible to reset the max peak and clipped samples counters by sending a SIGHUP signal to the process i e from another console killall v HUP ecasignalview 14 To monitor the input signal you can either use the soundcard s analog or in some cases digital monitoring functions by enabling line mic in monitoring us ing alsamixer ALSA aumiz OSS or some other mixer application Another option is to use ecasignalview to do the monitoring In this case the correct command is OSS input and outpu
24. t ecasignalview dev dsp dev dsp corresponding ALSA command ecasignalview alsa default alsa default Ecasignalview command line options allow you to fine tune the way moni toring is done increased refresh rate 20Hz ecasignalview r 50 alsa null larger buffersize 1024 samples ecasignalview b 1024 alsa null recording in mode 32bit 10channels 96000Hz with interleaved channels ecasignalview f s32 10 96000 i alsa null It can also be used with files and real time devices like JACK inputs and outputs monitor audio recorded by JACK system input first 2ch ecasignalview f f32 2 jack system null monitor audio from JACK application foosynth ecasignalview f f32 2 jack foosynth null play and monitor a file input ecasignalview foo wav alsa 6 2 2 Further Reading See ecatools 1 man page for a detailed listing of available command line options 6 3 Ecatools See ecatools 1 man page 15 Chapter 7 Advanced features 7 1 Audio loop devices Just by using normal chain connections it s not possible to route audio from one Ecasound chain to another One way around this limitation is loop devices They were introduced in Ecasound 1 7 0 7 1 1 Example of use An example use case where we route audio from chains 1 and 2 to chain 3 which is amplified and send to a soundcard output alsa cut note the second loop parameter is the loop id number it is used t
25. ulnerabilities setting Ecasound suid root is not safe Whether this is a real problem depends on the particular setup whether connected to a network or not any untrusted users with shell access The basic problem is that Ecasound or at least 2 0 and earlier doesn t contain any code for altering privilege levels If it is run with root privileges it does everything as root including forking external programs such as mp3 and ogg utilities and editors But all in all this shouldn t be that big of an issue for many users For noncritical uses just don t set the suid bit but run as a normal user If you have an untrusted setup and you don t want to login as root but still need to run in raised priority mode the following can help to limit the risk of suid root use cd usr local bin chown root ecausers ecasound chmod 4750 ecasound In other words the ecasound binary is set as suid root so it is run with root privileges but only root and members of the ecausers group can start it You of course first have to create the ecausers group to your system 25 The ideal solution would be that ecasound would not need full root privileges but privileges for changing scheduling and locking memory On recent Linux systems there are couple ways to achieve this The Realtime Linux Security Module LSM is one practical solution see http sourceforge net projects realtine 1sn and kttp Lwn net Articles 106009 This mo
26. ver efforts in that it has been designed from the ground up to be suitable for professional audio work This means that it focuses on two key areas synchronous execution of all clients and low latency operation Note that Ecasound must be compiled with JACK support enabled the with jack configure option to take advantage of the functionality described in this section 7 6 1 Basic Input and Output Let s start with how to play a file using Ecasound and JACK ecasound i foo wav o jack system 21 This will create a separate JACK output port for each channel of foo wav and automatically connect these Ecasound ports to the JACK system PCM output ports Note that ecasound does not allow to mix objects with different sampling rates without explicitly inserting samplerate conversion objects That means that if sampling rate of foo wav does not match the current JACK system rate the above command wil fail The connections creadted are as follows ecasound out 1 gt system playback_1 ecasound out 2 gt system playback 2 If foo wav was a four channel file the same command would connect all channels ecasound out 1 gt system playback 1 ecasound out 2 gt system playback 2 ecasound out 3 gt system playback_3 ecasound out 4 gt system playback_4 To record a file you d issue ecasound f 2 i jack system o foo wav ecasound f f32 2 44100 i jack system o foo wav Here we us
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