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   1 [18:41] <carla_s> all righty then, the official topic is intro to Audacity
   2 [18:41] <carla_s> I was thinking we could also do an intro to JACK, since that seems to be a hard one for a lot of users
   3 [18:42] <carla_s> maybe because it's confusing and not well-documented :)
   4 [18:43] <carla_s> should I be here or in #ubuntu-classroom-chat?
   5 [18:46] <carla_s> ok then let's get started, and many apologies for lateness
   6 [18:46] <carla_s> Audacity is reputed to be "easy", and in a sense it is
   7 [18:46] <carla_s> it's a great application with a nice interface and a lot of functionality
   8 [18:46] <carla_s> the tricky part is audio terminology
   9 [18:46] <carla_s> like audio quality settings
  10 [18:47] <carla_s> WAV files are pretty much universal. WAV is a large lossless format
  11 [18:48] <carla_s> To give an idea of what high quality settings are, a CD-ready WAVE file is 16 bits depth/ 44mHz
  12 [18:48] <carla_s> sampling rate
  13 [18:48] <carla_s> bit depth and sample rate are fundamental terms
  14 [18:49] <carla_s> bit depth controls dynamic range and signal to noise ratio
  15 [18:50] <carla_s> sample rate is how many times per second the analog signal is sampled for digital conversion
  16 [18:51] <carla_s> hang on-- looking up precise terms :)
  17 [18:51] <carla_s> good thing I wrote a book
  18 [18:52] <carla_s> so 16/44 means each individual sample is given a 16-bit value
  19 [18:52] <ClassBot> There are 10 minutes remaining in the current session.
  20 [18:52] <carla_s> 0-65,535
  21 [18:53] <carla_s> professionals record at 24- and 32-bit depths, and sometimes even 64
  22 [18:53] <carla_s> but that doesn't mean we need to go nuts-- more is not always better
  23 [18:54] <carla_s> CD quality recordings and even the low-budget onboard sound chips in modern PCs deliver higher fidelity than the studio gear of my youth (1960s and 70s)
  24 [18:55] <carla_s> the skill of the person making the recordings is much more important
  25 [18:55] <carla_s> and keep in mind how your recordings will be heard-- on good equipment in a quiet environment?
  26 [18:55] <carla_s> lo-fi portable devices?
  27 [18:55] <carla_s> vehicles?
  28 [18:56] <carla_s> Audacity, like many recording apps, records internally at 32-bit float
  29 [18:56] <carla_s> I make most of my master recordings at 24 bits depth/ 48 kHz
  30 [18:57] <carla_s> your desires may vary, of course, it's always what works for you
  31 [18:57] <carla_s> I don't hear a different between recordings made at 44 kHz or 48 kHz
  32 [18:57] <carla_s> but I do hear the difference between 16-bit and 24-bit
  33 [18:58] <carla_s> it's not necessarily a question of having great hearing, but more of having a trained ear and knowing what to listen for
  34 [18:59] <carla_s> having a high-quality master means you have a lot of headroom for editing and changes, and you can always export to lower quality levels
  35 [18:59] <carla_s> can't go higher
  36 [18:59] <carla_s> a common question is "how do I put my MP3s on CDs"
  37 [19:00] <carla_s> there are two types of CDs- Red Book audio-encoded for any  CD player, like in your vehicle or home hi-fi
  38 [19:00] <carla_s> and data CDs. You can put any audio file on a data CD-- WAV, FLAC, Ogg, MP3, and play it on your computer, because software media players support all formats
  39 [19:01] <carla_s> if you want your MP3s on a universal Red Book CD then they first need to be converted to 16/44 WAV
  40 [19:01] <carla_s> then written to CD as an audio project. not a data project
  41 [19:02] <carla_s> they're still lossy MP3 quality even after conversion to WAV
  42 [19:03] <carla_s> Audacity uses a special storage method for Audacity project files
  43 [19:03] <carla_s> it breaks every project up into a mass of little individual files, for speed
  44 [19:04] <carla_s> Audacity projects only play inside of Audacity. if you want studio masters to use in other audio programs you need to export them as WAV or FLAC
  45 [19:04] <carla_s> FLAC is nice because it's lossless compression, so you get WAV quality in a smaller file size
  46 [19:05] <carla_s> one difference is WAV supports 32-bit, while FLAC only goes up to 24-bit
  47 [19:05] <carla_s> muneeb asks about file size for screencasting
  48 [19:06] <carla_s> MP3s are good for this, even though to a lot of people's ears Ogg sounds better at low bit rates, and it's an open, unencumbered standard
  49 [19:06] <carla_s> though Ogb support is growing all the time
  50 [19:07] <carla_s> checking Audacity settings---
  51 [19:07] <carla_s> bitrate is bandwidth, not to be confused with bit depth
  52 [19:08] <carla_s> amount of data per second
  53 [19:08] <carla_s> (no, everyone cannot use the same measurements, that would be too convenient)
  54 [19:09] <carla_s> doing math...
  55 [19:10] <carla_s> one channel of 16/44.1 stereo has a bitrate of about 700k bits per second
  56 [19:10] <pleia2> carla_s: there are a couple of questions in -chat, would you like me to paste them here as they come up, or do you want to take questions at the end?
  57 [19:10] <carla_s> compare to 128k MP3
  58 [19:10] <pleia2> oh dear
  59 === ChanServ changed the topic of #ubuntu-classroom to: Welcome to the Ubuntu Classroom - https://wiki.ubuntu.com/Classroom || Support in #ubuntu || Upcoming Schedule: http://is.gd/8rtIi || Questions in #ubuntu-classroom-chat || Event: Ubuntu Open Week - Current Session: Introduction to Audacity - Instructors: carla_s
  60 [19:11] <ClassBot> Logs for this session will be available at http://irclogs.ubuntu.com/2011/05/06/%23ubuntu-classroom.html following the conclusion of the session.
  61 [19:11] <carla_s> server burp?
  62 [19:11] <pleia2> bot burp :)
  63 [19:12] <carla_s> I'm reading them as I go, and trying to work in answers in a somewhat sane fashion :)
  64 [19:12] <pleia2> ok, great
  65 [19:12] <carla_s> 128k MP3 is very lo-fi, a holdover from the olden days of slow Internet streaming and small storage in portable audio players
  66 [19:13] <carla_s> to my own ears 192k sounds pretty good. 320k is as high as MP3 goes. it is billed as CD-quality
  67 [19:13] <carla_s> it isn't
  68 [19:13] <carla_s> Ogg measures quality levels differently
  69 [19:14] <carla_s> it uses a variable bitrate (which MP3 also supports) so it's hard to pin down a specific bitrate
  70 [19:15] <carla_s> Ogg rates quality levels from 0-10, with 10 the highest
  71 [19:15] <carla_s> Ogg supports multichannel surround, which MP3 doesn't
  72 [19:15] <carla_s> well there is a version of Mp3 that does, but it's not well-supported, and ti's proprietary
  73 [19:16] <carla_s> an Ogg setting of 2 is roughly equivalent to MP3 at 122k
  74 [19:16] <carla_s> 112k
  75 [19:16] <carla_s> make than an Ogg setting of 3, sorry
  76 [19:17] <carla_s> Ogg levels 0-5 use lossy channel coupling
  77 [19:17] <carla_s> this means redundancies between left and right stereo channels are combined for smaller bitrate and filesize
  78 [19:17] <carla_s> you might notice a loss of stereo spatial imaging
  79 [19:18] <carla_s> when I make Ogg files I usually use 6. it sounds good and I don't hear a lot of difference at higher settings
  80 [19:18] <carla_s> of course my ears are getting old, which is why I always say "do what pleases you" :)
  81 [19:19] <carla_s> MP3 also supports variable bitrates. the advantage over a fixed bitrate is fewer bits are used in passages that don't need a lot of bits, and more bits in the sections that need them
  82 [19:20] <carla_s> Audacity lets you select ranges, like the Standard variable setting of 170-210k
  83 [19:21] <carla_s> if everyone is still awake, let's talk about 32-bit float, because it is a source of much confusion
  84 [19:21] <carla_s> 16, 24, and 32-bit depths are integer values
  85 [19:22] <carla_s> 32-bit float is a floating point value
  86 [19:22] <carla_s> I have forgotten the math behind this, so here is the laypeople explanation
  87 [19:23] <carla_s> 32-bit float is a 24-bit mantissa plus an 8-bit exponent
  88 [19:23] <carla_s> on a practical level this means two important things:
  89 [19:24] <carla_s> greater precision and very low noise floor
  90 [19:24] <carla_s> and you cannot play 32-bit float files anywhere but inside digital audio applications that support them
  91 [19:25] <carla_s> for most playback devices you need 8, 16- or 24-bit integer (also called linear)
  92 [19:26] <carla_s> when you are planning how to make your backups, plan on lots of hard drive storage
  93 [19:26] <carla_s> Audacity projects can be a bit fragile, and if Audacity's auto-recovery does not work then your project is lost
  94 [19:27] <carla_s> so I save both projects, and WAV masters
  95 [19:27] <carla_s> belt-and-suspenders to be sure
  96 [19:28] <carla_s> Audacity projects save information that can't be saved in WAV or FLAC
  97 [19:28] <carla_s> like track labels and other metadata
  98 [19:28] <carla_s> and they load a lot faster than WAVs or FLAC
  99 [19:29] <carla_s> there is a question, is the in 32-bit float, is the exponent signed?
 100 [19:29] <carla_s> I do not know
 101 [19:29] <carla_s> there, a definitive answer!
 102 [19:30] <carla_s> Audacity supports making multi-channel surround, like 5.1 and 7.1
 103 [19:30] <carla_s> you can export up to 32 channels
 104 [19:31] <carla_s> and if you have a playback device that supports 32 channels you win
 105 [19:31] <carla_s> but Audacity does not help you with mapping the channels correctly
 106 [19:31] <carla_s> you want to match them to your outputs: front surround, center, etc
 107 [19:32] <carla_s> the mappings vary with different audio formats, so I included some tables in my book for WAV, FLAC, and others I forget now
 108 [19:32] <carla_s> this is why I write howtos-- because I forget
 109 [19:33] <carla_s> you don't need to spend a mint on hardware
 110 [19:33] <carla_s> because as I said earlier, even inexpensive audio devices are techically superior to even studio equipment of yesteryear
 111 [19:34] <carla_s> for two-channel stereo recordings there is a vast wealth of great devices to choose from that don't break the bank
 112 [19:34] <carla_s> there are all kinds of USB audio interfaces for under a couple hundred dollars that are very good and easy to use
 113 [19:35] <carla_s> as long as they are USB class-compliant you don't have to worry about drivers
 114 [19:35] <carla_s> I will never understand why vendors would make USB devices dependent on special drivers. a lot of extra work for no good reason
 115 [19:36] <carla_s> USB interfaces are portable, and you don't have to worry about picking up internal noise
 116 [19:36] <carla_s> Behringer has a line of multi-channel USB mixers that run from around $100 to about $600
 117 [19:37] <ClassBot> There are 10 minutes remaining in the current session.
 118 [19:37] <carla_s> the most important component in your audio chain the is analog to digital/digital to analog converter
 119 [19:37] <carla_s> there are cheapos that sound bad. they introduce noise and distortion
 120 [19:38] <carla_s> you should be able to turn the volume way up before you hear any hum or hiss
 121 [19:38] <carla_s> A question about FLAC
 122 [19:38] <carla_s> I like FLAC
 123 [19:39] <carla_s> when you buy online music you often have a FLAC option. that is high quality in about one-third smaller size than WAV
 124 [19:39] <carla_s> FLAC support is still spotty, but if you're playing them on a computer-y device you're covered, like a home media server
 125 [19:40] <carla_s> WAV supports up to 32-bit, FLAC mxes out at 24
 126 [19:40] <carla_s> which is still plenty high quality
 127 [19:40] <carla_s> there are some other differences---
 128 [19:41] <carla_s> it is an open unencumbered format
 129 [19:41] <carla_s> it has several compression levels, from 0 to 8
 130 [19:41] <carla_s> these do not affect quality, just file size
 131 [19:42] <ClassBot> There are 5 minutes remaining in the current session.
 132 [19:42] <carla_s> it supports fewer channels than WAV
 133 [19:43] <carla_s> drat, can't find it
 134 [19:44] <carla_s> any questions? that was a rather random whirlwind tour
 135 [19:44] <carla_s> audacity is a great WAV editor, and great for making live recordings
 136 [19:44] <carla_s> the real power of audio editing is giving every voice and instrument its own track
 137 [19:45] <carla_s> Audacity supports unlimited tracks, until your computer keels over or your recording interface maxes out
 138 [19:46] <carla_s> it is CPU-intensive, and even though Audacity is not written to take advantage of multiple cores it runs a lot better on multicore machines
 139 [19:46] <carla_s> those extra cores take care of JACK and any other software you're running
 140 [19:47] <carla_s> thanks everyone for being here, congratulations and thanks to the Ubuntu team for putting on Open Week!
 141 [19:47] <ClassBot> Logs for this session will be available at http://irclogs.ubuntu.com/2011/05/06/%23ubuntu-classroom.html