#10045 HIGH 1.5-sof: XO-1.5 Record audio/video are out of sync with each other

Benjamin M. Schwartz bmschwar at fas.harvard.edu
Thu May 13 08:07:54 EDT 2010

On 05/13/2010 03:26 AM, James Cameron wrote:
> We discussed this briefly in team meeting this morning ... Record is
> writing an uncompressed stream to SD, before then compressing it in the
> "Save" step once the video recording is stopped.  (I could be wrong).
> This means that no matter what the size of the buffer memory, if the
> data rate from the camera exceeds the rate at which we can write to SD,
> there will be skips once a recording is long enough to fill the buffer.
> So we determine the data rate by choosing height, width, and frame rate
> from the camera.  We determine the maximum rate according to the choice
> of SD media.

If I understand correctly, Record does compress the video on the fly.
It's the audio that it writes uncompressed to disk for later compression
and muxing.  I don't know at what quality it performs audio recording, but
it might be as low as 32 KB/s uncompressed.


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