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New bloop slate app


Rakesh Anderson
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Is there no setting for 1/25 second? Would make the app more attractive to us Europeans...

I'm not sure why that would be important but, perhaps I misunderstand how the application works.

The bloop lights that were built into cameras (Arri BL, Eclair NPR, Bolex with MST motor, etc.) in the sixties and seventies all operated for a relatively long period. When tripped, they would flash frames and run an oscillator for six or eight frames. One synced using the last frame of flashed film opposite the last frame of tone.

Some versions incorporated an interesting sophistication to the scheme. Rather than outputting tone - actually, they usually tripped the internal oscillator in the Nagra rather than supplying a tone - they interrupted the sync pulse signal in the recorder. So, there was no audible tone but, for a half dozen frames, there would be no sync signal on the tape. Transfer machines were programmed to "listen" for the absence of tone and operate a marker pen on the mag film whenever it was encountered. The editor would find a visible sync mark on the track but the audio would be clean even during the slates.

I wonder if newer generations of equipment might feature a similar refinement. With file based recording, there is no longer a continuous sync or timecode signal that might be interrupted but the recording equipment now has a much broader range of recording capability. Perhaps the sync tone could be 30 kHz. Modern equipment can reliably record that tone, and the wave spike could be displayed, but it's inaudible on playback. (A variation on the "thumper" principal.)

David

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48 kHz Sample Rate = 24 kHz highest frequency (see Nyquist frequency)

That would work.

In fact, the frequency could probably be as low as about 15 kHz, maybe even 12 kHz, and still be good for that particular application. It's only necessary that it be sufficiently high that it either wouldn't be heard on playback or that it's possible to be Eq'd out. The Thumper systems work with a beat, if I recall correctly, around 30 Hz or 40 Hz. That's a frequency that people can hear and one even encounters it is certain music. (Also Sprach Zarathustra) But it's well below a frequency that is typically heard in normal speech and it's possible to filter it out so that the Thumper doesn't conflict with the recorded speech. In a similar way, a high frequency slate might not directly interfere with an ongoing interview.

David

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Why is it that new apps don't work with ipods older than ios 4.3?

Apple's latest programming tools will not compile for older, armv6 iPods/iPhones but are required for the latest, armv7/armv7s iPod/iPhones (at least to support the larger screen). It's apparently possible to provide binaries for all three architectures by installing two versions of the developer tools and combining the outputs of both. But it isn't easy and could introduce problems maintaining code on the two versions.

" 48 kHz Sample Rate = 24 kHz highest frequency "

48 kHz Sample Rate = <24 kHz highest frequency

To clarify, it is possible to represent a 24 kHz signal with a 48 kHz sample rate. We don't do so because without filters it would be a square wave, which is what we would recognize as digital overload if we could actually hear it. Similarly, frequencies approaching 24 kHz would also sound distorted which is why our sample rate isn't 40 kHz. The most important thing to know about the Nyquist limit is that trying to record frequencies above the Nyquist limit results in aliasing that produces frequency content below the Nyquist limit.

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Using this app on a shoot now and one thing I noticed was that the app doesn't flip with the phone. It would be great if there was an option to be able to flip the phone, so that the speaker with the beep is pointing up towards the mic. Just a suggestion.

Again, great job. We bought three copies, one for the DPs phone, the ADs and the directors iPad ;).

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Terrific - does what it does without being fiddly or toy-like (like most of the 'iPad Slate' apps). The only issue on my iPhone 3GS I have is the 1sec Tone selection results in the screen flashing red for 1 sec, but no audio tone. All the other bloop durations work fine. The 1sec duration works fine on my version-1 iPad. Not a big deal - for my needs this has swept all the other slate apps into the trash! It's great on iPad, by the way - pretty much fills the screen - perfect for quick broadcast chain sync checks too. Thanks a lot.

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