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Digital Audio Principles
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Sound tools pt. 2: Reverse and time compression/expansion


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Digital Audio Principles

with Dave Schroeder

Video: Sound tools pt. 2: Reverse and time compression/expansion

Let's look at a few other sound tools that are pretty cool. We will look at reverse and we will look at time expansion, or compression. So first, let's start with reverse. I will open that up from the AudioSuite, and as the name implies, it reverses stuff. I don't even need to preview it actually. We will just go ahead and go for it. I will make a copy over here, and we will process it. So what have we got? (drum sounds playing in reverse) Backwards. Very cool.
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  1. 50s
    1. Welcome
      50s
  2. 39m 10s
    1. What is sound?
      4m 15s
    2. Hertz and frequency response
      5m 34s
    3. Phase
      2m 39s
    4. Capturing audio
      3m 39s
    5. Sample rate
      6m 16s
    6. Bit depth
      9m 47s
    7. The waveform
      5m 3s
    8. Audio file formats
      1m 57s
  3. 7m 25s
    1. What is a digital audio workstation?
      2m 59s
    2. Typical DAW signal flow
      4m 26s
  4. 50m 33s
    1. What microphones do
      1m 57s
    2. Element types
      5m 0s
    3. Pickup patterns
      6m 51s
    4. Axis
      2m 52s
    5. Frequency response and the proximity effect
      5m 10s
    6. Phase issues
      1m 41s
    7. Microphone types
      8m 44s
    8. Miking vocals
      5m 39s
    9. Miking amplifiers
      2m 17s
    10. Miking drums
      10m 22s
  5. 16m 39s
    1. Cables and connectors overview
      2m 42s
    2. Balanced and unbalanced cables
      3m 19s
    3. Common cable types
      7m 13s
    4. Cable tips
      3m 25s
  6. 12m 16s
    1. What is an I/O device?
      1m 41s
    2. Analog to digital conversion
      3m 10s
    3. Tour of an audio interface
      4m 49s
    4. Interface considerations
      2m 36s
  7. 21m 5s
    1. What is a preamp?
      3m 21s
    2. Input levels
      5m 29s
    3. Padding
      2m 18s
    4. Phantom power
      2m 37s
    5. Phase reverse
      3m 4s
    6. Preamp demo
      4m 16s
  8. 12m 56s
    1. What is a mixer?
      5m 55s
    2. Input section
      1m 17s
    3. Channel strips
      3m 16s
    4. Master section
      2m 28s
  9. 18m 21s
    1. What is monitoring?
      2m 11s
    2. Speakers
      4m 47s
    3. Room considerations
      5m 43s
    4. Headphone types
      3m 50s
    5. Monitoring levels
      1m 50s
  10. 15m 23s
    1. What role do computers play?
      1m 36s
    2. Performance issues
      4m 11s
    3. Hard drives
      4m 38s
    4. Mechanical noise
      2m 10s
    5. Authorization
      2m 48s
  11. 6m 54s
    1. Planning for recording
      54s
    2. Doing a system check
      1m 26s
    3. Planning your inputs
      1m 42s
    4. The recording environment
      2m 52s
  12. 25m 52s
    1. Types of digital audio software
      38s
    2. Multi-track recorders/sequencers
      4m 56s
    3. Two-track recorders/waveform editors
      4m 55s
    4. Loop-based music production software
      5m 44s
    5. Plug-ins
      6m 56s
    6. Other varieties
      2m 43s
  13. 18m 59s
    1. Common components
      46s
    2. The transport
      2m 4s
    3. The toolbar
      3m 19s
    4. The Edit/Arrange window
      4m 42s
    5. The mixer
      5m 8s
    6. The file list
      3m 0s
  14. 19m 17s
    1. Setting up a session
      3m 30s
    2. Assigning inputs and getting signals
      3m 19s
    3. Input modes
      3m 28s
    4. Overdubbing and punching
      5m 14s
    5. Bouncing down
      3m 46s
  15. 19m 42s
    1. What is editing?
      1m 21s
    2. Waveforms
      2m 53s
    3. Making silent cuts and trims
      7m 1s
    4. Fades and automation
      8m 27s
  16. 1h 23m
    1. What are plug-ins?
      3m 0s
    2. Using plug-ins
      6m 11s
    3. EQs
      7m 4s
    4. Dynamics pt. 1: Compressors, limiters, expanders, and gates
      5m 40s
    5. Dynamics pt 2: Applying dynamic effects
      7m 2s
    6. Pitch shifting
      6m 14s
    7. Reverb
      9m 28s
    8. Echo and delay
      6m 23s
    9. Modulation effects: Phaser, flanger, and chorus
      9m 39s
    10. Sound tools pt. 1: About, gain, normalize
      7m 39s
    11. Sound tools pt. 2: Reverse and time compression/expansion
      6m 29s
    12. Sound tools pt. 3: Noise reducers, dither
      8m 11s
  17. 23m 43s
    1. What is MIDI?
      3m 6s
    2. Keyboard controllers
      1m 23s
    3. Computer-based virtual instruments
      1m 6s
    4. Control surfaces
      1m 6s
    5. Recording and editing MIDI
      12m 4s
    6. Virtual instruments
      4m 58s
  18. 27m 29s
    1. What is mixing?
      1m 54s
    2. Some common objectives
      3m 4s
    3. Some useful techniques
      5m 59s
    4. A quick mixing demo
      16m 32s
  19. 18m 48s
    1. What is mastering?
      2m 24s
    2. Sonic maximization
      9m 43s
    3. Final preparations and exporting
      6m 41s
  20. 13m 34s
    1. What is audio compression?
      2m 16s
    2. Popular formats
      2m 9s
    3. Bit rate, sample rate, and channels
      5m 42s
    4. Other adjustments and considerations
      3m 27s
  21. 15m 6s
    1. Essential gear
      7m 36s
    2. Voice recording setups
      1m 43s
    3. The voice production process
      5m 47s
  22. 10m 4s
    1. Analog vs. digital
      2m 48s
    2. Tube vs. solid state
      5m 6s
    3. The continual upgrade
      2m 10s
  23. 18s
    1. Goodbye
      18s

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Digital Audio Principles
7h 57m Appropriate for all Mar 02, 2007

Viewers: in countries Watching now:

Whether one is producing music, podcasts, game sounds, or film sound effects, Digital Audio Principles provides the tips and techniques that will make the project a success. Author Dave Schroeder explains the basics of digital audio production techniques and covers the essential hardware and software. He also discusses sound theory, frequency response, the range of human hearing, and dynamic range.

Subjects:
Audio + Music Audio Foundations Acoustics Microphones
Author:
Dave Schroeder

Sound tools pt. 2: Reverse and time compression/expansion

Let's look at a few other sound tools that are pretty cool. We will look at reverse and we will look at time expansion, or compression. So first, let's start with reverse. I will open that up from the AudioSuite, and as the name implies, it reverses stuff. I don't even need to preview it actually. We will just go ahead and go for it. I will make a copy over here, and we will process it. So what have we got? (drum sounds playing in reverse) Backwards. Very cool.

How about on a voice? I can kind of get some possessed sounds going. (garbled speech) So that's for the possessed podcast, for those of you who want to tune in. So reverse, it's pretty basic, pretty simple. You can use it for some pretty cool things. In music mixes, you can use a reverse cymbal hit as a nice transition into kind of different sections. Obviously, if you are doing sound design, you can use it to make some pretty interesting effects, different kind of shoops out into space and impacts and hits and things like that.

And also, maybe if you are doing a podcast and you wanted to kind of have something kind of lighthearted in there, and say, hey let's rewind that a minute, I don't believe you, you could hit that and kind of hear that backing up and say, okay. (garbled speech) Well, without the drums. (garbled speech) And then roll it again and say, let's hear that! (Female Speaker: This is episode 47) So there is ways you can kind of use it for fun. You can do kind of interesting things with it. The other thing I want to show you is time compression and expansion. This is another thing that is pretty much possible thanks to the digital world.

It wasn't really happening too much and very effectively before we had digital computers and we got to digitize audio. So it's really worth checking out. Again this is a file-level process. You can't use reverse or time expansion/ compression as an insert or a real-time plug-in. Remember earlier where we talked about pitch and we are kind of changing the pitch up and down, and there is a feature in there that allowed you to keep the rate of the performance the same so the time didn't change, just the pitch.

Well this is kind of the opposite. We can change the time without affecting the pitch, and it's very cool. I will go ahead and just show you a few examples of what's possible. Let me go ahead and delete our backwards track there, solo that out, and zoom in on it. And we can move this over here. Let's pick a couple words, just a short phrase, maybe this. (Female Speaker: This is episode 47) We will make it a little bit longer.

(Female Speaker: 2007. This is episode 47.) Let's say I want to make that take place a little bit faster. Well, I highlight it, and in my Plug- in window, I see the Source here on the left, which is the length of what we have got highlighted, and then the Destination, and right now there is no change. So its 4.6 seconds long, and the destination, the output of process, would be 4.6 seconds. I can drag a ratio here and change that and make it longer. So let's give that a shot. We will make it 7 seconds long.

(Female Speaker: 2007. This is episode 47.) So we have made a little bit slower. Now you can hear there is a little bit of artifact there, and that's one thing to keep in mind with most time compression/expansion stuff. You can use it, but only within reason. The greater the effect you ask for, the more chance you are going to get little artifacts, or little digital imperfections. I mean we are kind of asking it to do something pretty amazing. So I am going to undo that, and we will see. I bet we can probably get away with making it, maybe it's 4.5.

We could add another second to that, and it probably would still sound pretty good. (Female Speaker: 2007. This is episode 47.) And one of other thing you can do is go in and highlight each one of these little fellows and process them separately. We can also take this and make it shorter, so it happens faster. Take a second off that.

(Female Speaker: January 19th, 2007. This is episode 47.) (Female Speaker: January 19th, 2007. This is episode 47.) Pretty cool. So we can use this on the voice. We can also use it on instruments or on performances. If you have a little passages in a piece of music--the drummer maybe slowed down for a couple beats-- you can go in and try and apply this and speed them back up a little bit and shift things with it. Or you can use it if there is a couple of notes here and there that kind of get held too long. You can also go in and just individually grab those notes and slide them around.

But it's kind of fun to play with the time expansion/compression plug-in. If you are doing production for things like podcasts or TV commercials, and you know you want to get something to match up and you know that you have to make your production 30 seconds long and that's it, going in and kind of speeding up a few things a little bit here and there to kind of make sure you hit that deadline can help out a little bit. But again, you have to use it judiciously, because if you go too far--all people are pretty good listeners--and if we speed things up too much, people will know. And when people will hear something that seems kind of unnatural, unless it's there for kind of a comical effect, it throws us off a little bit, and it distracts us a little bit.

So if you are trying to create a podcast or something where you want people to be listening to the content of what you are saying, it's better to make sure that you deliver it in a way where the audio and production itself doesn't distract them, where they are sitting there saying, oh! That voice is sped up, as oppose to, wow! That's an amazing Pentium 7 computer Dave is talking about. Also, if you are working on like voiceovers that go with film where you kind of record the things out of sync or away from a film, you can use this to speed up or slow down little clips of the voice to try and make them match the mouth movements. Or if you are working against an animation, you can use this to change the speed the people are talking to kind of match sounds to images a lot better.

So time compression and expansion comes in really handy when you are trying to marry sound to picture. At any rate, regardless of what you are using these tools for, you will find that reverse and time expansion and compression are both really pretty cool tools and can be very helpful when you are working with audio.

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