[Lumiera] Audio editing

Ichthyostega prg at ichthyostega.de
Sun Jul 5 22:30:38 CEST 2009

hendrik at topoi.pooq.com schrieb:
> On Sun, Jul 05, 2009 at 05:15:38PM +0200, Christian Thaeter wrote:
>> Ichthyostega wrote:
>>> ... For everything I am aware off, the frame rate was fixed to a limited
>>> set of values dictated by hardware, eg. 8000, 44100, 48000, 96000,
>>> 192000, etc.

>>> Christian Thaeter schrieb:
>> That are sample rates, dunno if one wants to call single audio samples a 
>> frame :)...

yes, "audio sample frame" is a common term. Which seemed to have confused
me ;-)  because Juan probably referred to the NTSC video framerate (23.976)
-- thanks for pointing that out!

I think, for the most common video framerates, we should provide fixed
identifiers on the API/GUI (and internally represent them as rational numbers).

>> .... Even worse, a lot of (consumer) cameras clock drift depending on
>> temperature, moon-phase and mood, the audio sample rate is not exactly
>> 48kHz but some Hz more or less (i'd guess frame rates may drift too). Some
>> people told me that this gives noticeable audio desyncs depending if the
>> camera was warm or cold. We'll face endless fun with such things :).
Yes, can confirm that. Both image and sound framerate can drift on consumer
cameras, which gives you endless headaches esp. when filming a musical event
with several such cameras....

>> I think some automation for frame/sample rate fine adjustment controling
>> some noise gate (extend/compact silent phases) or frame drop (or doubling)
>> might be a forseeable tool to correct that.

we could try to find a solution here; but I'm rather sceptical with regards to
getting sound automatically synched to the image. Maybe a semi-automatic tool
could work. But even a tool of the sort "pin this (mouse click in waveform)
sound elm. to that video frame and stretch sound if necessary" would be a great
help for this tedious task...


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