When you seek you then need to decode until you get a picture, if this
is for playback or display. When you decode the picture you should get
a PTS. If you are not try turning on the AVFMT_FLAG_GENPTS flag. I
understand this flag correctly it will always generate a PTS even if
the stream doesn't have one.
I ended up creating my own little decode loop for seeking since i am
trying to display images as i seek. it basically has a little tight
decode loop that is not spread across threads.
Scott Andrew
On Jul 16, 2009, at 10:04 AM, Will Ross wrote:
On Jul 16, 2009, at 11:45 AM, Art Clarke wrote:
If you're not using libavformat to demux, then for many codecs
libavcodec
relies on you to set timestamps on objects. If you don't set them,
it
defaults to NO_PTS_VALUE which happens to be the number you see.
So, either set and manage timestamps yourself, or use libavformat
to demux
(you'll still need to worry about the time-bases of different
timestamps --
they are not directly comparable across different streams).
See the ffmpeg.c source code for some of the stuff it does to track
timestamps.
- Art
If I understand correctly, I am using libavformat to read the
streams, as I'm using the functions listed in avformat to read the
video files in (av_open_input_file(), av_find_stream()). I'm not
trying to do different streams, just one at a time, so that should
simplify things. My opening code is really close to that used in
Martin Böhme's tutorial, with some syntactic sugar for Objective-C.
My current code to seek to frames only works (well, it kinda/not
really works for all frames, but the P-frames show only the changes,
as they're supposed to) for keyframes. the duration of a packet was
found by decoding one packet and pulling duration out, and when I
want to go to frame n, I seek to n * packet.duration. The problem I
have is I have no way of knowing in code where I am.
-Will Ross
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