On 14/12/2005, at 4:21 PM, Trent Piepho wrote:
When you use -F 4 -p, the mpeg file has its framerate set to 30
fps, but there
are only 24 frames encoded per second. The encoder puts in repeat
field flags
that tell the decoder to do the pulldown, which has the effect of
converting 24
frames into 30 frames. So it's more correct to say that the
decoder contructs
30000:1001 video from a 24000:1001 source, as opposed to the other
way around.
I am guessing that these repeat field flags are not to difficult to
add to a stream.
As this program can modify an existing m2v stream
http://www.inwards.com/inwards/?id=36
(source is available and will compile on OSs other than windows)
And I am also guessing that the repeat field flags are distinct
enough for players, such as mplayer, to say, hey this is really a
23.976 progressive steram, I'll play it as such. I've seen mpeg
files that swap between 29.97 and 23.976 with pulldown. Some of the
video is in 23.976 progressive and some is 29.97 interlaced, mplayer
can detect these changes and will change it's playback mid stream.
I guess my confusion is, that the resulting mpeg stream is a fully
compliant 29.97 interlaced stream, and is played as such by players
that don't know about pull down, but these repeat field flags can be
added, detected and removed easily. I don't quite understand.
Mark
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