Sound, Video synchronization problem

[David Phillip Oster]

Warning:

I've gotten early reports that the movies Vidnik makes work fine on
the Macintosh, but when encoded by YouTube, the sound is out of
synchronization with the picture. I'm looking in to this, and will
report back here when I know more. -- David Phillip Oster May 12, 2008
8:38 AM PDT

[Mike Bogle]

I've had similar symptoms when recording via QuickTime using the H.264
codec. In that case changing the Recording preferences in (QuickTime
Player/Preferences/Recording) to Good (MPEG-4) fixed it; but from the
look of things Vidnik uses MPEG-4 already.

Great app by the way :)

Cheers,

Mike

On May 13, 1:59 am, David Phillip Oster <DavidPhillipOs...@gmail.com>
wrote:

[David Phillip Oster]

Quicktime is producing MPEG-4 encoded movies without an initial i-
frame. Other transcoders and players, when they encounter such movies,
drop the initial sequence of p-frames from the video, but not the
audio. That's how they get out of sync.

I'm making a change to Vidnik to force an initial i-frame on the
movies it produces. I'm planning to append to the start of the movie a
black frame followed by a white frame. That should force the encoder
to produce a movie with an initial i-frame.

I'll test, the upload a new version.

[David Phillip Oster]

Revised explanation:

Quicktime is producing MPEG-4 encoded movies with an edit list. The
first displayable frame of the movie is a b-frame, not an i-frame.

Other transcoders and players, when they encounter such movies, drop

the initial sequence of b-frames from the video. I'm making a change
to Vidnik detect that the first displayable frame is not an i-frame,
and rewrite those movies, such that the first frame is an i-frame.

I'll test, the upload a new version.

I'm using http://developer.apple.com/samplecode/MovieVideoChart/ to
view the internal structure of the movie. Erica Sadun's article on it
http://www.oreilly.com/pub/a/mac/2007/01/23/modding-apple-sample-code.html
was immensely helpful.