StretchFix

http://yano.wasteonline.net/software/stretchfix/ 2008-2016 Kevin C Dixon

Problem Definition

The effects of age on a tape can make it playback through the tape heads at varying speeds. If dubbing an old master tape to digital, a gunky tape can make this task difficult. The end result may be an un-listen-able, slo-motion, and totally worthless dub of the original tape master.

Solution

StretchFix uses a two step process to restore your audio files to "normal speed".

First, you load the SMPTE Linear Time Code track, as dubbed from your gunky tape. StretchFix then parses the time code to determine how much each LTC frame varies from real-time.

Secondly, given this data, it processes any tracks you select using a varispeed, to restore them to real-time.

Getting Started

1. Clone this repo
2. Clone submodules if you didn't already
3. Prepare libsamplerate (below)
4. Open StretchFix/StretchFix.xcodeproj

libsamplerate setup

libsamplerate needs the Xcode Command Line Tools, autoconf, and friends...

1. sudo xcode-select --install
2. brew install autoconf
3. brew install automake
4. brew install libtool
5. brew install pkg-config
6. Finally, in libs/libsamplerate, run ./autogen.sh
7. Run make all

Install/Run

Once you successfully build the StretchFix target and all its Target Dependencies, you must install the Audio Units. Copy the products sscau.component and secretrabbitau.component to ~/Library/Audio/Plug-Ins/Components/ You can run auval -s auol to see if the plugs in are present. This lists the "Offline" types of AudioUnits You should see

  auol srvs YSPf  -  StretchFix: SecretRabbitAU
  auol ssca YSPf  -  StretchFix: SSCAU

in the list somewhere.

If you modify these AudioUnits, you'll have to re-install them to see the changes at runtime. An enterprising hacker could probably make a post-build step to install these.