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2 Producing Sound

Many users have written to ask why they are unable to get Rosegarden to make any noise. It is the most common question asked on the rosegarden-user mailing list by far, and is especially troublesome for those newly migrating to Linux from Windows. Before we start Rosegarden for the first time, I want to explain what is necessary to pave the way, and have a good first experience. Some of you already know all this, and those of you who do are invited to jump ahead to the next chapter, where the interesting part begins.

The topic of sound covers two distinct areas that may or may not be codependent, depending on the hardware and software you have available. One the one hand, there are several requirements that must be met in order to play MIDI with Rosegarden, and on the other, it's necessary to get the JACK server up and running reliably in order to make use of Rosegarden's audio features. A working JACK server is also required to play MIDI with synth plugins, or to play more than one ALSA software synth at a time. Getting Rosegarden to make noise can be a complicated business, but hopefully I can help you deal with whatever set of circumstances you have before you. I cannot, however, cover every detail of getting every card working with every distribution. I'm afraid I have to leave some questions unanswered, lest this chapter become a book unto itself.

Here is a roadmap showing all the possible ways to produce sound with Rosegarden at a glance. It's quite daunting, I know, but I hope I can help you make sense of it:

2.1 Playing MIDI

MIDI under Linux is quite a complicated subject. The available hardware falls into three broad categories, each with its own special considerations. External MIDI hardware, internal hardware with ALSA support, and internal hardware without ALSA support. The latter category splits into ALSA soft synths and synth plugins, which are similar, but slightly different.

2.1.1 What's in My Computer?

If you have no idea what you have inside your box, and you have no idea how to configure any of this stuff, one good place to start is to have a look and see how far your distro has gotten you for free. Most modern distros should load ALSA in preference to OSS (the old sound system), and they should detect and configure a wide variety of soundcards for you automatically. KDE has a useful information center that can display information about your sound configuration. It will typically be found on the KDE menu under System -> Info Center, or you can run it manually by typing "kinfocenter" into an alt+ F2 run command box.

Here is a sample of its output, with explanations superimposed on the screenshot:

Different soundcards will have different features. Most of them, for example, will list nothing for "Synth devices."

2.1.2 External MIDI Interfaces

By far the least complicated, and most expensive way to play MIDI under Linux is to use real MIDI equipment. This can include keyboards, sound modules, and perhaps even MIDI guitars. A wide range of equipment is available for this purpose, ranging from comparatively inexpensive consumer keyboards to professional quality gear. The cost ranges from hundreds to thousands of dollars however, and this is not the way to go unless you are serious about MIDI.

If you're fortunate enough to have such equipment, then you probably already have some idea how to hook it up to your computer. If the equipment has the ability to produce sound on its own, as some MIDI keyboards do, then you may wish to use those speakers for MIDI playback. If your MIDI equipment has no speakers, or if you intend to record the audio output from this equipment, you may wish to connect the audio output from your keyboard or sound module to an audio input jack on your soundcard. This will allow you to route everything through the soundcard's mixer. There are several choices for external MIDI interfaces.

2.1.2.1 Joystick Port MIDI Adapters

The simplest, least expensive route is the joystick port MIDI adapter. These are found on many common, low-end soundcards, such as the Sound Blaster PCI 128 (snd-ens1371). It can be somewhat difficult to obtain a suitable Y-cable or MIDI box to connect to these, and you will probably have to procure one online. With the right adapter in hand, all that remains is to connect your equipment to the box or cable using standard 5-pin DIN MIDI cables. With the snd-ens1371 driver, and those for many similar cards, it's only a matter of making sure the snd-seq-midi and snd-rawmidi modules are loaded (using whatever mechanism your particular distribution provides for that function.)

2.1.2.2 USB MIDI

USB is supplanting traditional MIDI cabling, and several manufacturers are producing keyboards that plug directly into your computer using standard USB cables. There are also devices available which provide multi-port MIDI interfaces. These interfaces attach to your computer using a USB cable, and they provide several traditional 5-pin MIDI sockets.

2.1.2.2.1 USB Keyboards

Evolution manufactures several models that are known to conform to the standard USB MIDI specification, which are therefore compatible with Linux. Chris Cannam, one of the core Rosegarden developers, uses an Evolution-2 keyboard, and reports that it works using the snd-usb-audio module, which should probably be loaded automatically by hotplug. He imagines that most other manufacturers' wares are similar.

2.1.2.2.2 USB MIDI Interfaces

The Edriol UM-2 and mAudio MidiSport 2x2 are known to work under Linux. I have no experience with such things myself, I'm afraid, so I can only provide second-hand information.

Pedro Lopez-Cabanillas, a contributing Rosegarden developer, reports that getting the Edriol UM-2 working is as simple as plugging in the USB cable and loading the snd-usb-audio module, which should probably be loaded automatically by hotplug.

Pedro's USB MIDI Interfaces...

Pedro and Chris both report that the mAudio MidiSport interfaces are more difficult to get working. Pedro reports that "some of them require a firmware program to be loaded into the device's RAM before you can use it. There are GPL firmwares (package ezusbmidi) for the 1-port and 2-port devices (up to Midisport2x2), they are provided as RPM packages for Red Hat by CCRMA, and for Mandrake by Thac . There are also ready to use packages from AGNULA/Debian and Gentoo. Or you can tweak and compile the firmware from its sources." Chris reports that users with 2.6-series kernels may have difficulty using these devices. Pedro suggests that you have a look at the zero config environment information available from CCRMA if you are running Red Hat or Fedora.

2.1.3 MIDI without External Hardware

For those without external hardware to use, there are two remaining categories. A few soundcards have built-in MIDI infrastructure that ALSA can use. Everyone else will have to use some kind of software synth.

2.1.3.1 Cards with Synth Support under ALSA

This is the next easiest way to get MIDI working. So far as I know, this category only applies to those with soundcards based on an Emu chipset, such as the Sound Blaster Live!/Audigy series (snd-emu10k1), and the AWE 32/64 (snd-emu8000). I have a Sound Blaster Live! Value Edition myself, and can report that it's easy to get working, and it sounds reasonably decent.

2.1.3.1.1 SB Live! Modules

First, you'll need to ensure you have the proper kernel modules loaded, and that you are using the ALSA modules, which have "snd" in the name. If your distro has a nice utility for this purpose, use it. I have been unable to locate a graphical module-reporting utility that's universally-available. The only alternative I can give you that's assured of working across all distros is to head for the dreaded command line to issue a command like:

lsmod | grep snd

I have the following modules loaded for my own SB Live!:

snd-seq-oss snd-seq-midi snd-emu10k1-synth snd-emux-synth

snd-seq-midi-emul snd-seq-virmidi snd-seq-midi-event snd-seq

snd-emu10k1 snd-pcm-oss snd-mixer-oss snd-pcm snd-timer

snd-hwdep snd-util-mem snd-page-alloc snd-ac97-codec

snd-rawmidi snd-seq-device snd soundcore

If you don't see "snd" you almost certainly have the wrong (OSS, the old sound system) modules loaded, or no sound modules at all. Addressing that is beyond the scope of this book, due to there being so many differences between distros. I fear I have to refer you to whatever help resources your distro provides in that event.

2.1.3.1.2 Set the Mixer Volume

Next, you'll need to check to make sure you've turned up your mixer volumes. I will cover this card's rather complicated mixer in detail when I talk about managing various inputs and outputs for the purpose of audio recording. For the moment, it should be sufficient to ensure the "Music" channel volume is turned up. My mixer of preference is KAmix. Unfortunately, it is not widely available outside of SuSE, and you may have to compile it yourself. (I had to go to quite a lot of trouble to compile it myself for Debian.) It isn't the prettiest mixer, but it's the only one I've found that lets me control my SB Live! consistently and efficiently to get the results I want.

2.1.3.1.3 Load a SoundFont

Finally, you'll need to load a soundfont into the card. These cards use .sf2 soundfonts that are readily available. I'm not aware of a soundfont free enough to be included with any distribution of Linux, so you will most likely have to obtain one from the web, or perhaps from the CDs that came with your soundcard. I have had good luck with soundfonts from the Personal Copy website, but I make no warranty expressed or implied about the suitability or legality of their soundfonts, or any other soundfonts you might obtain on the web for any particular purpose.

Once you have obtained a soundfont, you need to load it into the card. There isn't currently any user-friendly way of managing this. I'm developing a utility for this very purpose, but I did not have time to finish it before releasing this book, and so I will make no further reference to it. In the meantime, your two choices are to run the command line utility asfxload , or to configure Rosegarden to load a soundfont for you at startup, via Settings -> Configure Rosegarden -> Sequencer -> General



2.1.3.2 Cards without Synth Support under ALSA

This is really the "everything else" category. It includes too many soundcards to list; each with its own set of modules. The Sound Blaster PCI and Ensoniq AudioPCI cards (ens-1370, ens-1371, ens-1373), and integrated snd-intel8x0 and snd-via82xx are probably the most common, but soundcards that fall into this category are legion. The process for getting them to play MIDI is similar in all cases.

2.1.3.2.1 Check your Modules

First, you need to ensure you have the necessary ALSA MIDI infrastructure by loading the following modules in addition to whatever other modules you require for your particular hardware:

snd-seq-midi snd-seq-virmidi snd-seq-midi-event snd-seq

snd-timer snd-rawmidi snd soundcore

(The above list was extrapolated from the previous SB Live! example, and may contain modules that won't actually load with your particular hardware. If loading one or more of the above modules fails, don't worry about it unless you later find your MIDI subsystem doesn't work.)

2.1.3.2.2 QSynth

The least complicated way to get one of these cards to play MIDI is to use QSynth. It is a simple to use ALSA soft synth that takes MIDI data as input and uses .sf2 format soundfonts to produce audio output. In its simplest configuration, it can use ALSA for audio output, avoiding the need to run JACK. If you already need or want to run JACK, it can connect its output to JACK instead. In this configuration, you can also use a variety of other ALSA soft synths such as Hydrogen and ZynAddSubFX, all sharing the same audio output. QSynth is the most useful for general music production, and so it is my focus here.

2.1.3.2.2.1 Configure the Audio Driver

The first decision you need to make is whether to use ALSA or JACK for output. I will cover starting and configuring JACK in detail in a moment. No matter which option you choose, both are configured via the Setup button. In this example, I'm using JACK. Take special note that I have adjusted the sample rate to match the sample rate I'm using with JACK, which is 48,000 Hz (for reasons I will explain directly.) Also note that I have checked [x] Auto Connect JACK Outputs. This allows QSynth to make its own default connection with JACK, which is very convenient.

2.1.3.2.2.2 Loading a SoundFont

Finally, it's necessary to load at least one soundfont. These are the same .sf2 soundfonts used by the SB Live! series of cards, and they are loaded via a different tab on the same setup page.

2.1.3.2.3 SynthPlugins

It is also possible to play using synth plugins. There is a FluidSynth-DSSI plugin that provides essentially the same functionality as QSynth, except that it's integrated directly into Rosegarden. I will describe it in detail when I talk about assigning instruments to tracks, because its configuration and use is entirely internal to Rosegarden. For the moment it is sufficient to know that it exists, and that it requires a working JACK server in order to function.

2.2 Playing Audio

In order to play audio you will need to run JACK.

2.2.1 What is JACK?

JACK is short for the Jack Audio Connection Kit. JACK is a flexible audio server that allows its client applications to share the audio hardware seamlessly, and to share a common transport. It provides flexible mechanisms for routing inputs and outputs to and from client applications using a jack-and-cable metaphor. It is geared toward the audio professional who wants to get the lowest possible latency and the best possible performance out of his or her hardware, but professional or not, it's something you need to come to terms with JACK if you want to play audio with Rosegarden.

2.2.2 Obtaining a Suitable Kernel

It is theoretically possible to run JACK and Rosegarden with an ordinary kernel, but I have never obtained acceptable results, even on machine with fairly high specs. CPU power and abundant RAM are insufficient to guarantee reliable performance, and you will, unfortunately, need to run a specialized kernel. Fortunately, the likes of AGNULA make it much easier than it used to be. It is now possible to do quality audio work in Linux without having to become an expert kernel hacker. I have to admit that I was impressed with this when I finally came around to trying it for myself. If you read any of the pre-release versions of this book, you may remember various rants I wrote about Linux audio along the way. I can now report that a happy JACK can be as simple as downloading one of AGNULA's (or CCRMA's presumably) kernels, installing it, and rebooting. The particular vagaries of installing the kernel are beyond the scope of this book, but I am running with these packages on my Debian box (laptop users might need to snag the PCMCIA modules as well):

alsa-modules-2.4.25-1-multimedia-686

kernel-image-2.4.25-1-multimedia-686

NOTE: Your mileage may vary if you want to use a newer 2.6-series kernel. As of this writing (2.6.8 is currently in Debian unstable), I have not yet heard of anyone having good results doing audio work with the new kernels. Some of the features patched into the AGNULA kernel have been incorporated into the mainline 2.6 tree, but not all of them. I recommend that you stick with a 2.4 series kernel for now.

2.2.3 Starting and Tweaking JACK

The simplest way to control your JACK server is to use qjackctl. It is a very useful utility that provides a convenient way to start and stop your JACK server, to play with various configuration parameters to find the best combination for your hardware, and to manage JACK connections between applications.

2.2.4 Configuring the JACK Server

To change how your JACK server is configured, use the Setup button. The process that follows will probably be tedious and time-consuming, but once you have discovered the "magic numbers" for your hardware, everything should continue to work thereafter. The patched kernel you installed allows JACK to have higher than normal priority, and this requires root privileges. You should configure JACK to start using "jackstart" so that you can run Rosegarden and JACK as an ordinary user.

The settings displayed are those that work best for me on my Sound Blaster Live!, and you may well have some fiddling to do from here. If you have more than one soundcard, you may need to twiddle the "Interface" setting. I don't actually have any experience in such a situation, so you are on your own to experiment in that case.

Discovering the best combination is a process of playing with the "Frames/Period", "Sample Rate" and "Periods/Buffer" settings. Your objective here is to find the lowest possible latency, as reported in the lower right-hand corner of the dialog. As you change settings, this number will show the results yielded by that combination. You want the sample rate high, and the frames/periods and periods/buffer low.

I suggest you dial up the lowest possible latency, click on OK, then try to start the JACK server with the Start button on the main dialog. If the server fails to start, come back to this dialog and keep working up, one setting at a time, until you find a combination that works. Many combinations of settings will probably cause JACK to fail immediately. You should quickly begin to get an idea of the range of possible values you can use that will actually work, and then you can home in on the ideal settings from there. (For example, it isn't possible to start JACK on my hardware with a periods/buffer other than two, so there is nothing for it but to use that setting and move on to a different parameter.)

2.2.4.1 The Evil XRUN

It's very important to avoid xruns. If you find a combination of low-latency settings that allow the JACK server to start, but which produce a flood of xruns, you're aiming too high. Xruns are reported in the main QJackCtl dialog. Ideally, you should see this:

If, on the other hand, you see something like this, you have trouble ahead:

You never want to see this much red. Seeing any red at all is really unacceptable, but you can probably get by so long as your xruns are few and far between. Xruns cause audio dropouts; clicks, pops, distortions, flanger-like effects. If you get more than two or three in the course of a day, you probably need to de-tune JACK a notch and trade some performance for reliability.

2.2.5 Managing JACK Connections

Rosegarden will establish sane default connections automatically. So will QSynth and Hydrogen, if you've configured them to do so. ZynAddSubFX and perhaps other JACK-aware applications do not do this. To see and change the connections, click on the Connections button. Making or breaking connections is a process of highlighting one or more items in the left pane and one or more items in the right pane, then using the Connect or Disconnect buttons as required.

NOTE: You can also use QJackCtl to manage ALSA MIDI connections. I do not recommend that you do so while you are running Rosegarden. Rosegarden has its own internal MIDI router, and it doesn't work properly if you change MIDI connections externally. However, if, for example, you want to play your Sound Blaster Live! or QSynth with your MIDI keyboard without running Rosegarden, you can use QJackCtl's MIDI connection manager to hook it up.


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