Category: DSP

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Audio from Video

Using video to generate audio.

jit.peek~ outputs an audio signal from video matrix data.

(jit.peek~ help)

from cycling74.com

At any point in the the process, matrix data can be tapped to produce an audio signal. Analyzing video is very much like analyzing audio. For example, using envelope following and spectral analysis. Here are examples.

examples

1. jit.peek~-additivesynth.maxpat (in Max/MSP examples/jitter-examples/audio)

Draw a song

By Adam Florin and Joshua Kit Clayton

2. Frame subtraction

By Adam Rokshar

https://reactivemusic.net/?p=7005

3. Sound Emotion2 – using Macbook built-in camera

By Andreas Wittich

https://reactivemusic.net/?p=9225

4. jit.peek~-osctrack.maxpat (in Max/MSP examples/jitter-examples/audio)

Derives rhythmic audio data from video. (Using bball.mov)

By cycling74.com

5. Whispering Heights (in Max/MSP examples/jitter-examples/3rd-party/image-to-spectral-filter/whispering_heights.maxpat)

Similar to above but uses video to create a moving spectral filter.

6. Wolframatic.maxpat  (in Max/MSP examples/jitter-examples/other/Wolframatic/)

Fractal generator also generates audio.

By R. Luke Dubois

 

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maxradio updates

Upgrade to Mac OS Max version.

Windows, runtime, standalone, and documentation upgrades still in progress…

changes

This is an interim update to add new drivers.

  • driver for rtl-sdr
  • minor bug fixes

download

https://github.com/tkzic/maxradio

instructions

  • Connect a radio
  • Open maxsdr7a.maxpat 

note: 1/23/2015 – the repository was really messed up – missing externals, etc., have reloaded. The local source is now at tkzic/maxradio

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VCR’s are analog TV transmitters

Any VCR with antenna output has a built-in RF modulator.

Generally they transmit on channels 2-4. Here are the US frequencies:

from wikipedia http://en.wikipedia.org/wiki/Television_channel_frequencies

The signal is weak, not intended for broadcast. Not legal to broadcast… but hypothetically, amplifiers and antennas could be connected.

This audio signal is from an iPod playing through a VCR received by rtl-sdr in Max on 65.75 MHz. (channel 3) using a random length wire connected to the antenna output.

 

Notes about RF modulators:

I have tried this with some small RF modulator boxes. One of the problems is that you need to send a signal to the video input, or the modulator won’t run. You can get a rough signal by patching one of the audio channels into the video input jack. Or a better signal by using the video composite output of a raspberry-pi. Although the VCR gives a much cleaner signal

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Pd signal streaming objects

Use streamout~ and streamin~ to stream audio over a local network

The ‘help file’ for streamout~ has an example. Change ‘localhost’ in the connect message to the local IP address of the target.