On 5/27/14 11:28 AM, wm4 wrote:
On Tue, 27 May 2014 17:10:55 +0530
sithruk sana <[email protected]> wrote:
thanks for the reply.
I am doing the same by queueing the packet as described in dranger
tutorial http://dranger.com/ffmpeg/ffmpegtutorial_all.html
This tutorial is prehistoric, and following it will cause you more pain
than not. Many things in it are just wrong or uses deprecated APIs. I
recommend pretending that this tutorial doesn't exist.
Normally, libavcodec decodes one frame for one packet. But you need
to deal with "codec delay": at first you won't get any decoded frames,
even if you put in some packets. Only later (when enough frames are
queued internally), you will get 1 decoded frame for 1 packet. (You also
need to feed it null-packets at the end of the video to get the last
frames.)
If I have a buffer of encoded units, which I know contains a complete
frame of encoded input, are you saying that I may have to pass multiple
sets of these before I receive the decoded results of the first buffer?
Or are you saying that I can submit chunks of a frame's worth of encoded
input, and (understandably) won't get a complete frame back until I pass
in enough data for 1 frame?
Does the term "packet" in your reply correspond to something specific,
as in, one "packet" of h264 encoded data corresponds to one NALU, or do
you mean, one "packet" refers to enough encoded data, no matter the
encoder, to make one frame?
There are others reasons why it wouldn't output a frame. If the video
frame is "damaged", you may need to set CODEC_FLAG2_SHOW_ALL or
CODEC_FLAG_OUTPUT_CORRUPT (forgot which one) to make lavc output them.
Also, it's possible to drop frames by setting skip_frame, but you
probably don't use this.
this is useful, thank you
Joshua Kordani
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